# A DC-DC converter for EVs, maybe via Kickstarter



## Tesseract (Sep 27, 2008)

About 2 years ago there was a thread discussing Evnetics possibly developing a DC-DC converter. The project was shelved mostly because I couldn't get the manufactured cost below $200, and then the locomotive drive system project came along and derailed (ahem) all other projects.

Well, we finally shipped off the prototype locomotive drive system to the customer so I've revisited this gaping hole in the market, except with the intent of making the DC-DC myself, because, again, it still wouldn't be possible for Evnetics to make it profitably - not alongside the DIY EV and locomotive drives, anyway.

And as explained in that thread from 2 years ago, I have already worked out most of the details for a 14V/50A DC-DC converter that can run on a very wide input voltage range of 100-400V.

So given that Evnetics can't make this product profitably, I've been contemplating funding the development and/or production of it via a Kickstarter campaign. This thread, then, is to discuss the technical details of the converter as well as the prospective Kickstarter campaign. For example, it seems to me that most of the products which have been successfully funded on Kickstarter were open source. I don't have a problem making this open source, but I'd rather not offer a kit for people to build this themselves because, a) it will be mostly surface mount and, b) I don't want to deal with the people who really shouldn't be building something like this buying the kit and attempting to build it anyway just to save $100-$200. And besides, I know from experience that it takes just as long to pack a kit as it does to simply populate the board with the parts.

However, that does leave a pretty big spread between the obligatory altruistic $10 pledge to give your support with nothing much to show for it, and the (estimated) $350 pledge for the assembled and tested product. Any ideas for intermediate rewards would be welcome, as this is where my imagination tends to fail me.

Finally, I used to run a small electronics design & manufacturing business, so I know from both that experience and from Evnetics that a lot more people will say they want your proposed gadget than will actually buy it. Funding the development - or the production of the first batch, at least - via Kickstarter would spread out the entrepreneurial risk rather than me shoulder it all by myself. Also, if this experience with Kickstarter turns out well then I (or Evnetics) will be much more inclined to use it to fund even more ambitious products like, say, an AC inverter or a drive for switched reluctance motors. Baby steps first, though.


----------



## gunnarhs (Apr 24, 2012)

Tesseract said:


> However, that does leave a pretty big spread between the obligatory altruistic $10 pledge to give your support with nothing much to show for it, and the (estimated) $350 pledge for the assembled and tested product. Any ideas for intermediate rewards would be welcome, as this is where my imagination tends to fail me.


Ok you can count me in, I have only seen the option between 
1) cheap and dangerous (due to low isolation standard)
2) integrated with controller (siemens)
3) very expensive ( I was going for that option)

So if you think you are able of doing a good DC/DC converter for voltage up to 400V and less than 500 USD I would very much like that


----------



## palmer_md (Jul 22, 2011)

I don't know anything about kickstarter, but I'm still interested in a quality dc-dc converter for $350-$400.


----------



## frodus (Apr 12, 2008)

Sounds like a great idea actually. There's also a gap at lower currents and 100-400V for Motorcycles, which may only need 20A or so. Not sure if that's easily done or not, but keep it in mind.


----------



## Yabert (Feb 7, 2010)

Interesting idea Tess. Good helping hand at the DIY market. Thanks.

But what would be the main gain over currently available product? Let say Mean Well SP-750 at 200$ (127-370VDC in, 13.5-16.5v out, 50A).


----------



## Hollie Maea (Dec 9, 2009)

I would be in at the product level of funding.


----------



## CKidder (Dec 12, 2009)

Unfortunately I'm all set for DC/DC converters so I can't say I'd be in for pledging to buy one with Kickstarter. I could probably do one of the altuistic pledges for nothing in return though. I would really like to see something like this succeed. Disclaimer: I haven't found your previous discussion about this so if I've gone over anything already said I apologize.

For tiers on kickstarter this is my initial brainstorming: You could have batches and make the first batch more money and each subsequent batch a bit less. This lets people who are eager early adopters get theirs first and people who aren't in as big of a hurry can hold off for a second or third batch. I have seen this done on kickstarter. Another idea might be to include wiring with more expensive pledges. If the unit would be externally fused maybe have that as an option as well. I'd imagine most converters maintain a fusebox in the car but if you could source something like that for people who need it then that might be a potential option as well. 

Another idea (maybe dumb): Maybe include an output that supports limited amperage but never turns off. You know, something that could support an ignition switch and maybe keep people's radio presets and such. This eliminates any reason to keep a small 12V battery for bootstrapping purposes.


----------



## gunnarhs (Apr 24, 2012)

Yabert said:


> Interesting idea Tess. Good helping hand at the DIY market. Thanks.
> 
> But what would be the main gain over currently available product? Let say Mean Well SP-750 at 200$ (127-370VDC in, 13.5-16.5v out, 50A).


The only option is SP-750-12V
These small details....
I need at least 400 V input, 
I need at least 14V out (13,5 is not enough, my not exceed 15V)
I would prefer better isolation than 100 MOhm per 500V
I would need the developer to have extensive experience with EV and it is a bonus to be able to bug him personally


----------



## Tesseract (Sep 27, 2008)

frodus said:


> Sounds like a great idea actually. There's also a gap at lower currents and 100-400V for Motorcycles, which may only need 20A or so. Not sure if that's easily done or not, but keep it in mind.


Yes, easily doable, though I would think it would be more useful to cover a lower voltage range rather than 100-400V. Are you trying to accommodate the RMS drive system by any chance?




CKidder said:


> ...Disclaimer: I haven't found your previous discussion about this so if I've gone over anything already said I apologize.


I put a link to it in the opening post. It drones on for many pages with me often waxing acerbic and cantankerous, as is my wont.



CKidder said:


> For tiers on kickstarter this is my initial brainstorming: You could have batches and make the first batch more money and each subsequent batch a bit less.


Interesting suggestion. Definitely not something I would have thought of. Can you provide some example projects which used this kind of tier system as I would very much like to take a closer look at it.



CKidder said:


> Another idea might be to include wiring with more expensive pledges.


This ain't the GEVCU with 30 something wires - it's just going to have 5 or 6 terminals - HVIN+, HVIN-, Chassis Ground, LVOUT+, LVOUT- (optional), IGNIN (optional - enables the converter, fed by 12V from ignition switch).



CKidder said:


> If the unit would be externally fused maybe have that as an option as well.


Not a bad suggestion, but a surprisingly expensive one relative to the overall cost of the product. Still, I'll look into it as it could be for a premium tier?



CKidder said:


> Another idea (maybe dumb): Maybe include an output that supports limited amperage but never turns off. You know, something that could support an ignition switch and maybe keep people's radio presets and such. This eliminates any reason to keep a small 12V battery for bootstrapping purposes.


Nope, this one is a bad idea on two counts: 1) without a 12V battery to buffer peak currents the output voltage will simply collapse every time, say, an electric power steering pump starts pulling 65A; 2) the DC-DC will draw current from the traction pack continuously to supply those "parasitic" 12V loads and to prevent overdrawing the pack would require adding intelligence to what is otherwise a dumb black box can be told what the battery pack voltage is so it can shutdown if it drops too low.

Believe me, simpler is better in this case - just hook the thing up to HV and 12V and let'er rip.


----------



## frodus (Apr 12, 2008)

Tesserect,
There's a big gap for the Electric Motorcycles with DC-DC converters. People do use some Vicor, but they're just the module, without terminals or filtering. Also, they basically stop at 96V for most of the 400W or smaller models, and then its off to TC Charger to get something else. Rinehart, Sevcon, Curtis, Soliton, are all over 100V ready controllers, but when you put them in a motorcycle, not sure we need 50-60A worth of 12V is all.


----------



## Tesseract (Sep 27, 2008)

Yabert said:


> But what would be the main gain over currently available product? Let say Mean Well SP-750 at 200$ (127-370VDC in, 13.5-16.5v out, 50A).


This is the central question, and the answer is simply that my converter will be designed for use in an EV. Either that is immediately worth the $150 premium to you, or you can effectively pay ~$550 for it later on... after having to replace the $200 Mean Well that, well, meant well, but couldn't quite handle the often-hostile EV environment.

1. The topology I've chosen (buck current-fed full bridge) is uniquely suited to handling wild swings in pack voltage. The typical commercial power supply is ill-equipped to handle this because it either uses a voltage-selector switch and so can only run over the range of around 275-375VDC, or it uses a PFC stage to cover the entire AC mains range but then suffers from extremely slow transient response because the loop bandwidth of the PFC stage needs to be well under the line frequency to meet the IEC power factor and distortion specs. 

2. It won't be bothered by ripple from the controller.

3. It will be in a closed box and passively cooled - no fan, no perforations - and designed for life outside at 50C, rather than in an air-conditioned office at 20-25C.

4. It will totally disconnect from the HV pack when shutdown, and will not place a parasitic drain on the main 12V output, either.


----------



## palmer_md (Jul 22, 2011)

Tesseract said:


> This is the central question, and the answer is simply that my converter will be designed for use in an EV. Either that is immediately worth the $150 premium to you, or you can effectively pay ~$550 for it later on... after having to replace the $200 Mean Well that, well, meant well, but couldn't quite handle the often-hostile EV environment.
> 
> 1. The topology I've chosen (buck current-fed full bridge) is uniquely suited to handling wild swings in pack voltage. The typical commercial power supply is ill-equipped to handle this because it either uses a voltage-selector switch and so can only run over the range of around 275-375VDC, or it uses a PFC stage to cover the entire AC mains range but then suffers from extremely slow transient response because the loop bandwidth of the PFC stage needs to be well under the line frequency to meet the IEC power factor and distortion specs.
> 
> ...


+1 I like it!


----------



## Tesseract (Sep 27, 2008)

frodus said:


> ...Rinehart, Sevcon, Curtis, Soliton, are all over 100V ready controllers, but when you put them in a motorcycle, not sure we need 50-60A worth of 12V is all.


No problem on making a smaller version that only puts out 20A, and while it will be less expensive, the price won't be directly proportional to output current. Off the cuff I'd say that halving the current would drop the price from $350 to $250. This is because while the basic design will be the same, most of the components will change: a different case, PCB, power transformer, MOSFETs, diodes, heck, even the values of the resistors and capacitors for loop compensation will change! So I don't know if that would be terribly attractive, pricewise, but it could make for an interesting stretch goal.

Oh, and a more general comment - I want honest feedback, not people blowing smoke up my *$$. [edit - this is not a jab at palmer_md  ]

Also, I'm pretty sure I can hit a price point of $350 for a 50A output unit. Near as I can tell, that means I would actually be competitive with the Chinese "made for EV" stuff like the Chennic.


----------



## gunnarhs (Apr 24, 2012)

Tesseract said:


> Oh, and a more general comment - I want honest feedback, not people blowing smoke up my *$$. [edit - this is not a jab at palmer_md  ]
> 
> Also, I'm pretty sure I can hit a price point of $350 for a 50A output unit. Near as I can tell, that means I would actually be competitive with the Chinese "made for EV" stuff like the Chennic.


I am full in.
The model I know for kickstart-like-project is based on subscription 
I would like to start with USD 100 / month for my part.
Meaning after 6 month I would have put in 600 USD and hopefully get one (prototype) converter.
First would not need to be certified, that is ok with the second (bought) one.
The rule who pays most gets first would apply of course..


----------



## Yukon_Shane (Jul 15, 2010)

I'm very happy to see you put this back on the table. If you can get close to the $350 price point I'm definitely in; that's a bargain in my books. 

With regards to the tiered supporter question, perhaps you could offer different case options: a cheap stamped steel option for a contribution of $350 and a nice aluminum case version for $500?

Keep up the good work.


----------



## Tesseract (Sep 27, 2008)

gunnarhs said:


> ...
> The model I know for kickstart-like-project is based on subscription


Another interesting suggestion, though I'm not quite sure how that would be implemented; it seems to reward me for procrastinating, which doesn't sound too good to prospective pledgers!? So I suspect I am missing something here, which is the real point of this thread: I am far more familiar with the design & manufacturing aspects of this project than I am with the Kickstarter part. 



gunnarhs said:


> First would not need to be certified, that is ok with the second (bought) one.


Ah, yes... certification. I am designing this with eventual certification in mind - and can do some basic "pre-compliance" testing myself - but understand that the cost to have a product certified for the EU can be *very expensive* and whether or not I pursue that will depend a lot on the success of the Kickstarter project and the volume of subsequent sales. So you European fellows are very much depending on your North American compatriots to make a good showing.




Yukon_Shane said:


> ...
> With regards to the tiered supporter question, perhaps you could offer different case options: a cheap stamped steel option for a contribution of $350 and a nice aluminum case version for $500?...


That is something I have considered, but if I had the freedom to use any case shape/design I wanted I probably would design the board differently! Anyway, here is the case I have tentatively selected:

YGKT enclosure

I chose it because of the following reasons:

1. I estimate it is large enough to contain all the major components (won't know that for sure until I start to design the board);
2. it's black so it won't be too noticeable;
3. it has mounting flanges;
4. it is split, so I will be able to bolt the power semis to the sidewall, maybe with a copper heat spreader (I don't expect losses to be high enough to warrant that, though);
5. and, finally, it is cheap.

And interesting to see you join the fray, as you were the one that started the previous thread 2 years ago


----------



## palmer_md (Jul 22, 2011)

Its a little different than the BUD you had in mind earlier, but I guess the case is not as important as the function. I don't need a pretty case since I don't intend to put it "front and center" when you open the hood.

http://www.budind.com/view/NEMA+Die+Cast+Aluminum+Box+With+EMI_RFI+Shielding/ANS-Series


----------



## Tesseract (Sep 27, 2008)

palmer_md said:


> Its a little different than the BUD you had in mind earlier, but I guess the case is not as important as the function..


Correct. Also, that Bud case wasn't all that attractive, really, and was rather expensive - $56, IIRC. If you all think the $40 premium in price for the Bud box is worth it, well, now is the time to cast your vote.


----------



## palmer_md (Jul 22, 2011)

Tesseract said:


> Correct. Also, that Bud case wasn't all that attractive, really, and was rather expensive - $56, IIRC. If you all think the $40 premium in price for the Bud box is worth it, well, now is the time to cast your vote.


I vote no for cost, but I really don't know the other considerations such as the shielding, sealing and such that the Bud seems to offer. I'd say its an engineering decision and its outside my expertise. As far as looks, you are correct, the less expensive box probably looks better.


----------



## gunnarhs (Apr 24, 2012)

Tesseract said:


> Another interesting suggestion, though I'm not quite sure how that would be implemented; it seems to reward me for procrastinating, which doesn't sound too good to prospective pledgers!? So I suspect I am missing something here, which is the real point of this thread: I am far more familiar with the design & manufacturing aspects of this project than I am with the Kickstarter part.


Ok the same here I would be the worst salesman ever I think, so I have to get advice from some friends on this part. Here is one of the site used in Iceland similar to kickstarter , the karolinafund
http://www.karolinafund.com/project/index.
It is the same type of projects which are successfully funded
1) Their funding target is 1500-3000 EURO
2) They have 50-100 backers
3) Most common backup is about 20 EURO
4) The outcome is a product which could cost 20 Euro each or a bit more.
5) Funding was raised in less than 30 days
6) Product was in many cases delivered 30 days after the complete funding
7) Successful fundraisers had at least one successful product before.

So it is same for 300.000 (Iceland) as for 300.000.000 market (USA).
(only difference USD instead of EURO  )

It is a bit hard to read into the backers mind but we tried...
1) Backers are not investors, they are potential buyers
2) (Early) Backers are ready to loose the money invested
3) Later backers are the result of herding, they don't want to miss the opportunity to join the successful buying
4) Very few are ready to lose more than 20 bucks
5) No interest after 6 months (much less after 1 month)

So what to do if you have a project which funding might be 5 to 10 times the size of most common success regarding funds and time?
Points 4) and 5) are a obvious problem, 
Also that backers can only afford a certain amount and they do not if they are not a bit sure of the funder. So this typical funding websites may not be the answer but rather working in a known community.
The model of subscription has the same target (buy a product) but offers less risk for backer and also fundraiser.
1) Expected product price will be devided in affordable parts, monthly payment for example
2) There is always a possibility to back out if necessary (could be a 30% repayment rule or another rule up to certain amount). 
3) Benefit of (early?)high backing would be first to receive (the Tesla effect)
4) Deadline for early funding, goals must be clear. this could be realized for example with paypal.

1. Step startup 
To start the product 50% of the total funding goal must be reached at day X (less than 30 days for example). This could be paid on a paypal-account with a payback-option until day X. If goal is not reached, then the product will not be started. Full repayment is easy.

2. Step work start
After day X the (conceptual) work will begin. At this time both fundraiser and backup have committed. the fund in step 1. will not be repaid. Next payment will result when next goal has been reached. Meaning design and cost of product will to be have fixed. This is the ugly way of the compromise (other will be to expensive)

3. Step production phase. 
Before this begins, Second payment must be maid, again there is a option to back out before it results. Here backing out would still leave an (time limited) option of turning back later at the cost of getting later delivery. The payment from 1. could act like a future price-off for the product. The risk is still that there will never be a product.
If there is a lot of backout the fundraiser has two options
a) To delay the product until further raising has been achieved
b) To stop the product and compensate the ones that paid the second payment, either with repayment or with an open source contribution.

4. Delivery prototype phase
Only to backers which have backed up at least the prototype price.
The higher the backup, the earlier the deliverment.
Other than backers can ofcourse buy but at higher price

5. Complete. 
Some backers have their product, other backers which have paid less or stepped out earlier have a sort of price off of the product based on their backing (could be considered as prepaid up to a certain amount). 

Just ideas...


----------



## steelneck (Apr 19, 2013)

Tesseract said:


> .. it's just going to have 5 or 6 terminals - HVIN+, HVIN-, Chassis Ground, LVOUT+, LVOUT- (optional), IGNIN (optional - enables the converter, fed by 12V from ignition switch).


Great! Keep It Simple Stupid. Today many engineers seem to have forgotten what good engineering is, implementing bells and whistles that just complicate things, sometimes to the point of making it silly. Keep it simple and elegant, bolt on and it just works, things like that is good engineering and often it demand a bit more thought from the engineer than those complicated things that try to do everything, like a Swiss knife that can do everything but is no good for anything.



Tesseract said:


> .. simply that my converter will be designed for use in an EV.
> 
> .. It will be in a closed box and passively cooled - no fan, no perforations - and designed for life outside at 50C, rather than in an air-conditioned office at 20-25C.


Yes. This is needed, but do not forget about -35C also.

Right now i am in the process of converting an old Ford Granada, any day now i will be ordering a Soliton 1 and a Kostov K11 (a bit overkill but i think the Jr. will be just a tad too weak). When i thought about about the 12V issue i did not find a converter i could consider reliable enough, so i made up my mind to use an alternator driven by the EM. Not the most elegant solution, but time tested, very cheap (used unit) and almost reliable in extreme. Things under the hood of a car has to withstand temps from very cold to quite hot, rain, humidity, snow, salt, dirt and dust, even a hot water high pressure wash and minutes later drive out in the winter and -20C. Most cars handle all this just fine and i think EVs should do the same. OK, the high pressure wash is extreme, especially combined with freezing temps minutes later, not all cars can take that.

If there is a unit i can buy from you before i get to the point of installing my 12V supply, you can probably count me in as a customer.


----------



## Rob A (Feb 7, 2010)

I'm in, where do I sign up?

I have avoided putting a DC-DC converter in the car because of all the failure stories in the forums. I am currently running an alternator off the tail shaft of the motor. It seems to work ok except whenever I am stopped I am running off of the battery. It gets a little nerve racking watching the volt gauge go down while waiting for a green light.


----------



## gunnarhs (Apr 24, 2012)

Rob A said:


> I'm in, where do I sign up?
> 
> I have avoided putting a DC-DC converter in the car because of all the failure stories in the forums. I am currently running an alternator off the tail shaft of the motor. It seems to work ok except whenever I am stopped I am running off of the battery. It gets a little nerve racking watching the volt gauge go down while waiting for a green light.


We have a similar solution in one with the only difference that the (AC-induction motor) is always on minimum at 500 RPM. In our case the alternator powers both power-steering and 12V battery like in the gasoline version. This solution is not an option when using the Siemens-Motor for example and it makes our setup in this car inflexible.
In the other cars we have cheap DC/DC. The problems with it have can be listed in the forum and adressed in this thread quite well , bottom line a DC/DC-converter MUST be built for EV-use.


----------



## Tesseract (Sep 27, 2008)

steelneck said:


> Today many engineers seem to have forgotten what good engineering is, implementing bells and whistles that just complicate things, sometimes to the point of making it silly.


Yep - that is precisely my design philosophy: "eschew obfuscation".



steelneck said:


> ...do not forget about -35C also.


Right. I do tend to gloss over low temperature operation, living in sunny and tropical Florida (where a cold front is coming through right now, dropping the temperature to a frigid 15C...).

I was aiming for -25C; -35C might be tough to swing. There is no avoiding the use of electrolytic capacitors in something like this, and most of them are only spec'ed down to -25C (where their ESR has already doubled, btw). 



steelneck said:


> Things under the hood of a car has to withstand temps from very cold to quite hot, rain, humidity, snow, salt, dirt and dust, even a hot water high pressure wash and minutes later drive out in the winter and -20C. Most cars handle all this just fine and i think EVs should do the same. OK, the high pressure wash is extreme, especially combined with freezing temps minutes later, not all cars can take that..


I agree that all of this is desirable and the ideal to strive for, but practically speaking, making the device truly waterproof - as in, you can spray it from any direction with a garden hose for several minutes with no ingress - would be very difficult for one man to do with off-the-shelf components. 

So I am aiming for "water resistant", which to me means it will tolerate the occasional incidental splashing from a puddle or condensation, but not, say, the direct and continuous spray that might be kicked up from the tires while driving in the rain. 

Also, even if one starts with a waterproof box - like the Bud box that palmer_md keeps referring to (ANS-3809) - that can, and often will, change once connectors are installed. In this case, I will almost certainly use the same type of barrier terminal strips as is used on the Soliton controllers. Not technically waterproof, but can be made decently water-resistant by applying a little silicone to the backside before mounting.


----------



## Tesseract (Sep 27, 2008)

Rob A said:


> I'm in, where do I sign up?


I'm still figuring out the Kickstarter thing and I'd like to nail down the rest of the design details like selecting an enclosure, getting quotes for the custom magnetic components, etc., so maybe a few weeks away from launching the Kickstarter campaign?



Rob A said:


> I have avoided putting a DC-DC converter in the car because of all the failure stories in the forums. I am currently running an alternator off the tail shaft of the motor....


Yeah, this is what I recommend people do now, even though it is kind of a kludgy solution. All these past 5 years I kept thinking that someone would surely come out with a decent dc-dc converter for EVs and, well... I finally realized that if not me, then maybe no one... unless y'all want to pony up for the 2.2kW Delphi that is bidirectional (useless) and has a minimum input voltage of ~220VDC, IIRC.


----------



## Tesseract (Sep 27, 2008)

gunnarhs said:


> Ok the same here I would be the worst salesman ever I think, so I have to get advice from some friends on this part. Here is one of the site used in Iceland similar to kickstarter , the karolinafund
> http://www.karolinafund.com/project/index.


That was an excellent post, so I gave you a point for your green block collection 

I'll have to think on your comments some more. I might very well conclude that the subscription model is not the way to go, but at least it will be a better informed decision.


----------



## brainzel (Jun 15, 2009)

Only a hint, but 15V is much to high for a four cell LiFePO4 (nor lead acid) auxiliary battery for a backup.
14.4V would be max, 13.6 would be great.
So if the output is adjustable, that would be nice.

Michael


----------



## Tesseract (Sep 27, 2008)

brainzel said:


> Only a hint, but 15V is much to high for a four cell LiFePO4 (nor lead acid) auxiliary battery for a backup.
> 14.4V would be max, 13.6 would be great.
> So if the output is adjustable, that would be nice.


Yeah, I figured it was only a matter of time before someone asked for adjustable output voltage. I happen to think there is no advantage over simply fixing the output voltage at 14.0V, and at least a couple of disadvantages to making V_out adjustable, but if you want to make a case for it - rather than just say you want it - I'm open to being persuaded otherwise.


----------



## gunnarhs (Apr 24, 2012)

Tesseract said:


> That was an excellent post, so I gave you a point for your green block collection
> 
> I'll have to think on your comments some more. I might very well conclude that the subscription model is not the way to go, but at least it will be a better informed decision.


Well thanks. I will give the credit to my friends
I forgot to mention that this subscription idea was really an exception used in this ?***? project here : http://www.karolinafund.com/project/view/139
(not every backer but there were some dedicated)
So everything is possible in this circus at least... , not sure that fits everywhere


----------



## toddshotrods (Feb 10, 2009)

I have a bit of, indirect, experience with Kickstarter Projects (KP), from being a member of the community workshop (CIF). The expansion into the wing I was in was made possible by a successful Kickstarter Project. The actual Project was to have a "Grand Opening" event to celebrate the expansion/doubling of size that was before my unit and, because they doubled the amount, Alex grabbed another unit - facilitating my 2-year, fully sponsored studio, journey there. Since then, I have watched a handful of CIF members and affiliated organizations/people do their own KP; some successful, some not. I was supposed to do my own, part of which was to purchase a Shiva from you, but ultimately decided not to.



What I found is a successful KP is a LOT of work. Most of the successful projects I saw were the result of a massive promotional effort. For that month, it was non-stop selling and promoting and pushing and sweating.
It's a typical numbers game, meaning the more people you reach, the better your chances of success. The most successful (the ones that doubled or tripled their requests) had large networks, and they tapped them, and worked them really well. I believe CIF's total reach, through members, newsletter mailing list, FB page, Twitter, and (most importantly) the organizations it interacts with frequently, was around 20,000 people. IIRC, less than 10% of those actually backed the project.
Don't immediately count out the "talkers" - the people who say they would buy your project, but actually never do (I think I just pointed at myself). A significant portion of the funds raised often comes from those people, and people who have no active interest in what you're doing, but want to support a good cause (part of the premise of Kickstarter).
Most successful projects start off with a big _dose_ of pledged money, then there is a lull about midway through, and a final push over the cliff near the end. If you start strong, you boost the confidence of the fence straddlers, and if they feel the rush near the end people begin to want to see you succeed and pledge, up their pledges, spread the word, etc.
Don't underestimate the work it might take to make all that happen. There are those projects that take off and almost self-fund, but most successful projects are the result of a lot of hard work in promoting them. Considering the size, and nature, of our little cottage industry - I would at least _plan_ to work my azz off.
Be wise and strategic with backer awards. Almost every successful Kickstarter Project I have seen has resulted in more work to fill the backer awards than to do the thing that was promised. It's easy to underestimate that, but with your real-world product development experience, you have a better idea of what you're promising. I'm not talking money here, because they all were very good about budgeting the awards into the amount requested - it was the work required to fill the awards that was underestimated; especially when they also had to complete the project. This burden increases exponentially when the awards are not directly related to the Project. That is the main reason I never did mine - I had no direct product to promise and most of my focus and time would have been spent making and shipping BS. The nail in my KP coffin was realizing that most of my Team was completely unreliable and that all of that work was going to fall on my few dedicated, hardworking, interns and volunteers; and ultimately, squarely, on my shoulders. It was just too far off track...
There are people/companies that will do the unrelated awards for you, but that (of course) means you need to request more money to pay them.
It's a typical sales game - how you present and promote the KP means as much as _what_ you're actually trying to do. In this case, if I were you, I would go the whole "save the Earth" route and try to reach out to every "Greenie" you have access to. A lot of people would probably be willing to contribute $10 for a good cause that helps "save the Earth", and often for no more than a simple mention on your website, or a certificate... I've seen simple awards like we'll shout your name from some specified location, or we'll plant a tree (on our tree farm that we make money from) in your honor, etc. Those people were giving because they supported the end goal, not for a "prize" (and shouting their name sounds cool, planting a tree is a good thing to do, etc)...
I've attached a PDF with a couple documents from Kickstarter. I had more research but can't find it - might have accidentally deleted it, or if it was CIF's they may have deleted it from their Google Drive.


----------



## dougingraham (Jul 26, 2011)

I am using a Vicor and while I have not had any problems with it there are some issues which your proposed device fixes. I have three of the 5 volt 40 amp modules in series. I trimmed them down to 4.53 volts so I have 13.6 volts which I float across a 4S 8 AH LiFePO4 pack. This all works great except for the following things I don't like.

1) There is a 7ma leakage when the Vicor is off. If I add the three 40A boosters this becomes 70ma which is why I don't have them anymore.

2) There is a significant inrush current such that I have had to fuse it with a 20A slow blow. A 10A fuse was inadequate and I am certain this inrush will eventually destroy the contacts used to turn it on.

3) The fan whine.

4) This is not even remotely water resistant.

5) It is physically too big. And while I would not consider it heavy it is more than necessary.

Your proposed converter addresses all of these issues. The only thing it doesn't have (but was mentioned) is the adjustable output voltage. I would prefer 13.6V to float my LiFePo4 buffer battery (3.4 volts per cell.) 13.8 would be a good choice for those who want to use a Lead Acid car battery. 12.6 would be good if your choice was a 3S LiPo battery. How about making this a selectable option inside the sealed case. Come up with four voltages selectable by a dip switch or dip pin jumpers. Anyway I think a somewhat adjustable output is desirable to match the buffer battery acceptable float voltage. I don't like the idea of a trim pot at all and I am sure you don't either for a number of reasons.

I would buy your device this minute if it could be adjusted to a safe level to float my buffer battery.

Thanks for considering this project. It is an essential EV component and I think you have come up with a good set of specifications.


----------



## GerhardRP (Nov 17, 2009)

Tesseract said:


> <snip> Any ideas for intermediate rewards would be welcome, as this is where my imagination tends to fail me.
> 
> Finally, I used to run a small electronics design & manufacturing business, so I know from both that experience and from Evnetics that a lot more people will say they want your proposed gadget than will actually buy it. Funding the development - or the production of the first batch, at least - via Kickstarter would spread out the entrepreneurial risk rather than me shoulder it all by myself. Also, if this experience with Kickstarter turns out well then I (or Evnetics) will be much more inclined to use it to fund even more ambitious products like, say, an AC inverter or a drive for switched reluctance motors. Baby steps first, though.


From the other comments, it seems that the project will be much more likely to succeed if it is done as Evnetics rather than Tess.
That also opens another backer award possibility that, when some production goal is reached then the support amount could be used as a rebate for the purchase of a different item from the Evnetics product line.


----------



## toddshotrods (Feb 10, 2009)

GerhardRP said:


> From the other comments, it seems that the project will be much more likely to succeed if it is done as Evnetics rather than Tess...


I would kind of agree with that - at least affiliated/associated with Evnetics, if not from it, to tie into the company's history of providing top notch DIY products "for the good of the world", probably literally at their own expense (compared to what could have been accomplished in the name of "profit" with the same resources).

That's the kind of stuff that makes people commit on Kickstarter. It's not a store, and Kickstarter doesn't want people to use it like one. It's a place to support things, and obtain support for things, that people believe in enough to open their wallets. More _cause_ oriented. Remember my journey was financed by people backing a celebratory event - because they believed that CIF is a great asset to their community.

One more (critical) point:


Shoot a video. That opening video can be everything. Kickstarter recommends it, and every successful KP I've seen had a video that got the point across quickly and convincingly. It's not absolutely necessary, but it tugs at the heart, and purse strings, (arguably) better than anything else.


----------



## Hollie Maea (Dec 9, 2009)

The easiest Kickstarter campaigns are those in which the primary pledge level is a copy of the product, as this would be. In these cases, people are essentially giving an advance for the product. The biggest challenges to overcome are marketing the kickstarter to a group of people who trust your and want the product. But since you have a great reputation on this board, and it is a product that is really lacking, I think it will be doable. Since it's not a "mortgage your house" level of project, as an inverter would be, and since you are not viewing this as your road to riches, I think you will have no problem finding enough people willing to put an advance down to "spread out the entrepreneurial risk".


----------



## toddshotrods (Feb 10, 2009)

Hollie Maea said:


> The easiest Kickstarter campaigns are those in which the primary pledge level is a copy of the product, as this would be. In these cases, people are essentially giving an advance for the product. The biggest challenges to overcome are marketing the kickstarter to a group of people who trust your and want the product. But since you have a great reputation on this board, and it is a product that is really lacking, I think it will be doable. Since it's not a "mortgage your house" level of project, as an inverter would be, and since you are not viewing this as your road to riches, I think you will have no problem finding enough people willing to put an advance down to "spread out the entrepreneurial risk".


In that case, you will probably have (maybe) a dozen or so people who are serious and ready to buy now (a lot of _interested_ others will prefer not to be early adopters, and wait a bit, but may have been interested in supporting the "cause", possibly for a future discount certificate/price guarantee or something).

Just targeting the immediate DIY community (not just this board), I would use one of the other fundraising sites that don't require you to meet your target to be funded. You get what was pledged regardless of the final amount. That eliminates the play-to-win, challenge, aspect of Kickstarter. It's more like a committed, organized, group buy.


----------



## Tesseract (Sep 27, 2008)

toddshotrods said:


> I have a bit of, indirect, experience with Kickstarter Projects (KP)...


More good stuff - excellent post and thank you for taking the time to write it. My only possible counterargument is that this project is almost certainly going to be a lot smaller in scale than your CIF ones. As in, I only need about 20 people to go for the $350-$400 pledge to make this worthwhile, and will probably cap that number at 40 so I don't overextend myself. I need to raise about $10-12k to cover the cost of developing the converter and building 20 of them. And let's face it, if I can't convince 20 people to pledge for the actual product just with this thread then, well, maybe it really isn't worth doing, eh?

Which segues nicely to your last post where you estimated a similar number of people who will want to "buy it now":



toddshotrods said:


> ...I would use one of the other fundraising sites that don't require you to meet your target to be funded....


Hmm... the only other one I have heard of is Indiegogo, but I've gotten the impression (from other forums) that there are a lot of charlatans and fraudsters on there, so only really obvious/simple things succeed. For example, I found this project on the "most popular" page which looks ingenious and which I am going to back: snap-strap.


----------



## Tesseract (Sep 27, 2008)

Hollie Maea said:


> ...But since you have a great reputation on this board, and it is a product that is really lacking, I think it will be doable.


YYes, trust me: I have a "spectacular aura about" [sic]. 



Hollie Maea said:


> Since it's not a "mortgage your house" level of project, as an inverter would be, and since you are not viewing this as your road to riches, I think you will have no problem finding enough people willing to put an advance down to "spread out the entrepreneurial risk".


Clearly someone pays attention to what I write...


----------



## toddshotrods (Feb 10, 2009)

Tesseract said:


> More good stuff - excellent post and thank you for taking the time to write it...


De nada. It's the least I could do, since I still have yet to _buy_ something from you. 





Tesseract said:


> ...My only possible counterargument is that this project is almost certainly going to be a lot smaller in scale...
> 
> ...Which segues nicely to your last post where you estimated a similar number of people who will want to "buy it now":...
> 
> ...


Gotcha. Give my brain a bit to access, or think what person's brain to access, and I'll post info/links. There are more purpose-oriented fundraising sites, including one or a couple where you can even "invite" the prospective backers - like from this thread, directly. So, that way every one knows everyone, and it's a simple, professional, transaction...


----------



## Tesseract (Sep 27, 2008)

dougingraham said:


> ...Come up with four voltages selectable by a dip switch or dip pin jumpers. Anyway I think a somewhat adjustable output is desirable to match the buffer battery acceptable float voltage. I don't like the idea of a trim pot at all and I am sure you don't either for a number of reasons.


I, too, think an adjustable output voltage - in and of itself - is desirable, it's just that I can't think of a way to implement it that doesn't compromise one or more of the following: 1) vibration tolerance (applies to shorting jumpers, dipswitches and, definitely, trimpots); 2) weather-resistance (e.g. - opening the case to flip a dipswitch would defeat silicone sealant applied "at the factory"); cost (using a case with an integral gasket will be more expensive); sensitivity to noise (e.g. - adding two terminals for an external trimming resistor exposes the feedback loop to the outside world... a world that includes a big, bad motor controller very close by).

I really have given the design of this thing a lot of thought, but if y'all are fine with paying a good $50 more for a case that has an integral o-ring/gasket to keep it sealed after opening it up, and are also fine with the inevitable reduction in vibration resistance because of the electromechanical bits, then I will amend the design specifications.



GerhardRP said:


> From the other comments, it seems that the project will be much more likely to succeed if it is done as Evnetics rather than Tess.


I know we are already on p3 of this thread, so the opening post is but a distant memory, but in it I explained that Evnetics can't make the proposed dc-dc converter for enough of a profit to matter at a price point of $350, and that is before Seb goes bat-_guano_-crazy with the CNC and a billet of aluminum.


----------



## dougingraham (Jul 26, 2011)

Tesseract said:


> I, too, think an adjustable output voltage - in and of itself - is desirable, it's just that I can't think of a way to implement it that doesn't compromise one or more of the following: 1) vibration tolerance (applies to shorting jumpers, dipswitches and, definitely, trimpots); 2) weather-resistance (e.g. - opening the case to flip a dipswitch would defeat silicone sealant applied "at the factory"); cost (using a case with an integral gasket will be more expensive); sensitivity to noise (e.g. - adding two terminals for an external trimming resistor exposes the feedback loop to the outside world... a world that includes a big, bad motor controller very close by).


I agree with all of that. So the conclusion is the factory sets the output voltage when you place your online order. To change it you send it back in and pay some extra. How does that sound?



Tesseract said:


> I really have given the design of this thing a lot of thought, but if y'all are fine with paying a good $50 more for a case that has an integral o-ring/gasket to keep it sealed after opening it up, and are also fine with the inevitable reduction in vibration resistance because of the electromechanical bits, then I will amend the design specifications.


I know you have given it a lot of thought. It is pretty much exactly what we need. I would pay $50 extra but would rather do what I mentioned above. I mean how often are you going to want to change this after the fact. The answer is almost never.


----------



## Tesseract (Sep 27, 2008)

dougingraham said:


> ...So the conclusion is the factory sets the output voltage when you place your online order. To change it you send it back in and pay some extra. How does that sound?....


I can live with that. I don't think I am going to accommodate a 3s LiPo pack, though - firstly, I don't see too many people crazy enough to go that route and secondly, headlights are noticeably dimmer if the "at battery" voltage is 12.6V. So two voltage choices, 13.6V for LFP and 14.0V for Pb, but with 14.0V the default option, because a top-balanced 4s LFP pack would be perfectly happy with that voltage.

That said, I have been looking at enclosures once again and found this ugly sonuvabiscuit which has an integrated silicone gasket to achieve an IP67 rating (essentially waterproof): Bud IPS-3935. Mounting ears are available, too, for an extra $4.10.


----------



## steelneck (Apr 19, 2013)

Tesseract said:


> So two voltage choices, 13.6V for LFP and 14.0V for Pb, but with 14.0V the default option, because a top-balanced 4s LFP pack would be perfectly happy with that voltage.


Perfect. A simple little switch behind a rubber cap in the casing. Or, if you want a trimpot to get a bit wider voltage range, but that could mess things up if someone try to push things a bit too far, so the switch would do just fine.


----------



## toddshotrods (Feb 10, 2009)

steelneck said:


> Perfect. A simple little switch behind a rubber cap in the casing. Or, if you want a trimpot to get a bit wider voltage range, but that could mess things up if someone try to push things a bit too far, so the switch would do just fine.


You missed some key words there steelneck! No consumer accessible switch, and you probably void your warranty if _you_ open it and change it.



dougingraham said:


> I agree with all of that. So the conclusion is *the factory sets the output voltage* when you place your online order. To change it you send it back in and pay some extra...
> 
> ...I mean how often are you going to want to change this after the fact. The answer is almost never.





Tesseract said:


> I can live with that...


----------



## bhayman (Feb 17, 2011)

Tesseract said:


> So two voltage choices, 13.6V for LFP and 14.0V for Pb, but with 14.0V the default option, because a top-balanced 4s LFP pack would be perfectly happy with that voltage.


That works for me. I prefer the 13.6v option for working with my 4s LPF accessory battery.

I had planned on a DC-DC converter for my build, but after reading about so many failures/issues I just opted to spend the money on an extra 4 100ah cells as my accessory battery and avoid the DC-DC converter/alternator route. For over a year now, this has worked out quite nicely as I wait for an affordable and well-built DC-DC converter to hit the market. 

If you go the Kickstarter route, I'm in.

-Bryan.


----------



## toddshotrods (Feb 10, 2009)

Fundable is one, but still an all-or-nothing format. Though they do have a flat monthly rate, instead of the (roughly) 10% Kickstarter and Amazon nab off the top.

I'll keep trying to remember the other one I was thinking of, that I think lets you keep whatever you raise. Actually, if you're basing it mostly on a small group, mostly from this board/thread, that you're sure will show up, Indie-Go-Go might not be a bad option. I would just want to avoid the pressure of making that line in the sand.

The last two CIF members I watched were 50/50. The one, a natural saleman, was still pretty far off halfway through and he pushed really, really, hard for the last two weeks and made it - to buy a laser cutter for his biz (that upcycles old materials into new stuff, usually on a contracted basis). The other, not so much the salesman, tried his hardest and missed. He had a more community oriented, good-for-all, hydroponics biz that teaches people how to grow healthy food, almost anywhere. I would have thought people would dig deep to help him, since he's actually, actively, trying to help their great little city - nope. He was completely stressed out by that deadline, and still seems a little different to me.


----------



## Duncan (Dec 8, 2008)

I am notoriously tight fisted - but I would put my name down for one


----------



## Tesseract (Sep 27, 2008)

steelneck said:


> Perfect. A simple little switch behind a rubber cap in the casing. Or, if you want a trimpot to get a bit wider voltage range...


The only problem with that suggestion is that waterproof switches are expensive: $20-$40 is typical. I would rather spend that money on a case with an integrated gasket and put a slide switch inside that the end-user can flip.



toddshotrods said:


> You missed some key words there steelneck! No consumer accessible switch, and you probably void your warranty if _you_ open it and change it.


If I go with an enclosure that requires silicone to seal it against water intrusion, then opening it up will void the warranty, but if I go with, e.g., that Bud enclosure with an integrated o-ring gasket, then no worries. I'm not too concerned with people ripping off my idea - in fact, I will probably provide the schematic with the converter (my only obstruction to doing that is I don't want to get deluged with tech support requests from people who want to build it, but don't know which end of the soldering iron to hold).


----------



## gunnarhs (Apr 24, 2012)

Tesseract said:


> The only problem with that suggestion is that waterproof switches are expensive: $20-$40 is typical. I would rather spend that money on a case with an integrated gasket and put a slide switch inside that the end-user can flip.


Please do. I would prefer that too. And for me it would be best to have the switch internally (I always need 14V, due to regulations in Europe I have to have a 12V battery inside and it will always be a Pb in my case) .
I would ifor my part want to avoid open the case, but would be fine if I could do that in case of any "Emergency".

PS: We have a "waterproof" case with silicone from Kelly, it does one good thing, we can see (on the colour of it) the actual time of the year  (spring/summer/autumn/winter)


----------



## toddshotrods (Feb 10, 2009)

Tesseract said:


> ...people who... don't know which end of the soldering iron to hold).


 At least they would have that wisdom _burned in_, when they healed enough to call you.


----------



## rwaudio (May 22, 2008)

Tesseract said:


> The only problem with that suggestion is that waterproof switches are expensive: $20-$40 is typical. I would rather spend that money on a case with an integrated gasket and put a slide switch inside that the end-user can flip.
> 
> 
> 
> If I go with an enclosure that requires silicone to seal it against water intrusion, then opening it up will void the warranty, but if I go with, e.g., that Bud enclosure with an integrated o-ring gasket, then no worries. I'm not too concerned with people ripping off my idea - in fact, I will probably provide the schematic with the converter (my only obstruction to doing that is I don't want to get deluged with tech support requests from people who want to build it, but don't know which end of the soldering iron to hold).


What about using a decent relay inside and just bringing out the coil terminals to your terminal strip? A jumper wire from the 12v/Ign or ground line to the appropriate relay or relays could select the desired trim voltage. 

That or you have a trim pot inside and set the customers desired voltage at the time of ordering put some goop on the trip pot and seal it up.

No need to make it too complicated, but I would require some sort of variable voltage.


----------



## Tesseract (Sep 27, 2008)

toddshotrods said:


> At least they would have that wisdom _burned in_, when they healed enough to call you.


I wish that were true, but just read the posts on this page of valerun's open source charger thread for several counterexamples. No offense to the participants in said thread, I'm just saying they really should have ordered the pre-assembled version of the charger... 




rwaudio said:


> ...No need to make it too complicated, but I would require some sort of variable voltage.


No to trimpots, no to relay. And why do you need the output voltage to be variable, anyway?


----------



## Tesseract (Sep 27, 2008)

There have been some useful suggestions over the last few pages, some of which I am going to implement. So to nominally stay within the remit of the "Technical Discussion" subforum (not that the crowdfunding stuff isn't valuable - far from it), I thought a post stating the design goals in more detail - and the changes that have been made to them as a result of this thread - would be timely.

1. Input range of approximately 100-400V. I might be able to extend the high end a little more depending on how well the prototype behaves.

2. Output of either 13.6V or 14.0V, and 50A max. (ie - 700W max)
a. Output voltage selectable by internal switch or shorting jumper.

3. Secondary side current sensing and a combined CC/CV regulation loop to allow for graceful handling of high peak current loads [edit: also allows paralleling]

4. Change back to an enclosure that uses an integral o-ring in the lid to maintain water-resistance even if the lid is removed to change the output voltage setting. 

5. Draw no power from either the HV or LV sides when turned off. This means all power to operate the converter must either be supplied or controlled by the ignition switch. More specifically, I have chosen to use a a separate "ignition in" terminal to which switched 12V (nominal) must be supplied for the converter to operate. (NB - I was going to make the IGNIN terminal optional, but decided to simplify my life by putting the housekeeping power supply on the secondary side).

6. Design for EU EMC requirements - testing/certification to those requirements, however, is quite expensive and so would maybe make for a good "stretch goal" on Kickstarter (or whatever crowdfunding site is used, if any).

7. The specific topology for the converter is a cascaded synchronous buck without an output capacitor which directly feeds a full bridge (aka - a "buck current-fed full-bridge").

8. I will probably use self-driven MOSFETs as synchronous rectifiers on the secondary side, mainly to reduce losses to a level at which even a die-cast aluminum case can be used as a heatsink, and not so much to improve efficiency, per se.

9. Intrinsic protection against reverse polarity and controller ripple on HV input - both will help converter meet EU EMC requirements, too.

10. Estimated price is now somewhere between $350 and $400.

I've worked out plenty more details but these are the top-level ones.


----------



## dimitri (May 16, 2008)

I'll buy one, Jeff. I am on my second DC/DC, which is kept alive by extra inductor on the input side, but I feel its only a matter of time till it bites the dust, literally, since its not sealed and has fans blowing dust thru it


----------



## bwjunkie (Jul 31, 2013)

off topic sorry, i'll post this in chit chat


----------



## rwaudio (May 22, 2008)

Tesseract said:


> No to trimpots, no to relay. And why do you need the output voltage to be variable, anyway?


Because as my name implies audio is my background, I wouldn't be just powering headlights and ignition. I want the flexibility to use Li-ion or LiFePO4, depending on what type of amplifiers I use and what kind of voltage they work best at. 

I have a waterblock and a bunch of Vicor modules to make my own, but haven't gotten around to making all of the other pieces I need, and it would only be splash proof at best, your product already sounds better than what I would put together.

Buying something that was designed by a very competent individual specifically for EV use at a fair price is quite desirable, and I'm sure I'm not the only one with that point of view (even if the voltage isn't adjustable the availability of such a product is very welcome).


----------



## Tesseract (Sep 27, 2008)

rwaudio said:


> Because as my name implies audio is my background, I wouldn't be just powering headlights and ignition. I want the flexibility to use Li-ion or LiFePO4, depending on what type of amplifiers I use and what kind of voltage they work best at.....


Okay, I'm not going to put in a trimpot just so you can tweak amplifiers, but I will put in a couple of vias on the board to make it easy to wire in an external variable resistor. However, note that I will have to limit the adjustment range to not interfere too much with the stability of the control loop. And don't ask for more than 14.0V because then I have to change the number of turns on the transformer or raise the minimum voltage, and that would annoy me greatly...


----------



## rwaudio (May 22, 2008)

Tesseract said:


> Okay, I'm not going to put in a trimpot just so you can tweak amplifiers, but I will put in a couple of vias on the board to make it easy to wire in an external variable resistor. However, note that I will have to limit the adjustment range to not interfere too much with the stability of the control loop. And don't ask for more than 14.0V because then I have to change the number of turns on the transformer or raise the minimum voltage, and that would annoy me greatly...


That's more than I would ask for, thank you for making that possible.


----------



## crackerjackz (Jun 26, 2009)

Id be in but only if I could get it in pieces to build it ! so I could bitch that you don't have instructions and blow shit up  !!! ... 


more seriously .... I honestly think you have a good idea going . I presently have a chennic which is brand new actually since my ev isn't finished  .... once it is finished and running should be around june . I would very probrebly be interested since I know this is the weak part of my build . but it was a cheap way around a lot of problems with my inspection process ect in quebec . if need be id be up to helping funding with a somewhat of deposit say 50 or 100 until id be ready to pay the rest and change out my chennic type dc dc ...


----------



## weber (Apr 22, 2009)

Sounds like a much needed product, Tesseract. We have a 720 V battery split into halves and we have been runing two MeanWell HLG-240H-15A's, one off each half, and paralleling their outputs by running each to the 12 V battery on a separate wire with a separate fuse at the battery end.
http://www.meanwell.com/search/HLG-240H/HLG-240H-spec.pdf

A 320W version is also available
http://www.meanwell.com/search/hlg-320h/default.htm

These are passively cooled in a sealed case (IP65) and are designed for 50degC ambient. They are rated for 431 Vdc (277 Vac + 10% * sqrt(2) ) and have a PFC stage. Although they are potted, they have a trimpot for adjusting voltage, whose access is via a plastic "chimney" through the potting, which is sealed with a rubber plug. We need this continuous adjustment so we can make them share current equally.

We recently had one fail for unknown reason. 
http://forums.aeva.asn.au/weber-and-coulombs-mx5_topic980_post49858.html#49858
So your mention of their inability to deal with input voltage transients is of interest. Thanks.

I would encourage you to allow continuous adjustment from 13.6 to 14.4 V. I see a lot of other people want user adjustment too, even if they have to open the case. Would a 10 turn trimmer be more stable? Couldn't the circuit be made so if the trimmer goes open circuit you get the lowest voltage, 13.6 V?

I'd also encourage designing for operation up to 450 V input to allow for regen braking in a nominally 400 V system and to allow for use with the Tritium WaveSculptor200 AC motor controller. 
http://tritium.com.au/products/wavesculptor200-motor-inverter/


----------



## Tesseract (Sep 27, 2008)

weber said:


> ...we have been runing two MeanWell HLG-240H-15A's, one off each half, and paralleling their outputs
> ...
> We need this continuous adjustment so we can make them share current equally.


I wouldn't rely on a trimpot setting the output voltage to ensure two converters share current equally over long periods of time, and definitely not in a high vibration/wide temperature environment. The output voltages will inevitably diverge with the lower voltage converter supplying little, if any, of the load current until the higher voltage converter goes into current limiting. Unless both converters have a true constant current mode then they will start oscillating, as the load current will switch back and forth between them as they each go into and out of current limit. Eventually one of them blows up, and then for some reason the system behaves much better, even if too much load current is being demanded of that remaining converter.

So, once again I see no upside to a continuously adjustable output voltage. 



weber said:


> I'd also encourage designing for operation up to 450 V input to allow for regen braking in a nominally 400 V system and to allow for use with the [product link deleted]


And just how many people are running that competing drive system at over 400V??? Unless it is more than 10 - and all of them commit in writing to buying the converter I design - I can't really justify increasing the cost of the buck stage to accommodate them. Understand that most people over here run systems in the 120-150V range, and the vast majority of all EVs worldwide - probably 95%, or 2 sigma on ye olde bell curve - run a pack voltage in the range of 100 to 350V.


----------



## bwjunkie (Jul 31, 2013)

dougingraham said:


> I am using a Vicor and while...
> 5) It is physically too big.


Which model are you talking about? because I was thinking this thread would be comparable to the Vicor Maxi (500w) which seems fairly small.



Tesseract said:


> I don't have a problem making this open source, but I'd rather not offer a kit


If the schematic/design alone was open source you could leave the idea of a "Parts list" or "DIY kit" to some other thread or person.
-josh


----------



## Brute Force (Aug 28, 2010)

What sort of connector is being considered? Please say it's an automotive grade weatherproof type and not screw terminals...

I'm keenly interested in this development!


----------



## dedlast (Aug 17, 2013)

Tesseract,
I'm wondering if, instead of variable output, would it be possible/cost-effective for you to put two outputs on it? One "low" voltage at 13.6 or whatever and the other "high" voltage at 14.0 or whatever. That would allow you to do the factory seal on a better looking case and give those who "need" it, a choice of outputs. I'm thinking that would double the output circuit component count, though, which puts a crimp in the cost effective part of the question.

Bill


----------



## palmer_md (Jul 22, 2011)

Tesseract said:


> And just how many people are running that competing drive system at over 400V??? Unless it is more than 10 - and all of them commit in writing to buying the converter I design - I can't really justify increasing the cost of the buck stage to accommodate them. Understand that most people over here run systems in the 120-150V range, and the vast majority of all EVs worldwide - probably 95%, or 2 sigma on ye olde bell curve - run a pack voltage in the range of 100 to 350V.


Not that this matters too much since what you said above is true, but the Renault/Leaf packs that were just sold at EVTV were all ~395v packs. I'm not sure if anybody is going to use them as is in series. I suppose many are going to turn the pack into three parallel sections of ~130v, which is right back into your "vast majority" voltage range. But if some are going to keep them in series and feed the DMOC645 then there will be some folks with this higher pack voltage out there. I'm not sure it is worth re-engineering unless we hear that there are a lot of these folks, but just thought I'd throw that out there to consider.


----------



## toddshotrods (Feb 10, 2009)

If a person has a 600-750v pack, that is wired as two sub-packs in series, is there as issue with tapping one DC-DC off one of the sub-packs?


----------



## Jan (Oct 5, 2009)

toddshotrods said:


> If a person has a 600-750v pack, that is wired as two sub-packs in series, is there as issue with tapping one DC-DC off one of the sub-packs?


You'll have a very serious out of balanced pack every day. 

I'm wandering if you could connect two converters in series in that case, and parallel the output?


----------



## Coulomb (Apr 22, 2009)

Jan said:


> I'm wandering if you could connect two converters in series in that case, and parallel the output?


Yes, that's what we do with our MX-5 (Miata). Or will when we unparallel and series our half-packs. That's why we want *continuously* variable output voltage, so we can balance them.

We confirmed today that with our long independent cables to the battery at the other end of the car, the two MeanWell supplies don't oscillate, and share pretty well. But the voltage drop across those long leads is reducing the charge current, and we need to do something to fix that. We can shorted the leads, but then when emergency services chop the lead to the auxiliary battery, the DC/DCs could keep the contactors pulled in and the battery pack lethal.

Our half packs are just under 400 V each, so we're likely not a consideration here. Also, two 50 A DC/DC supplies in parallel is way overkill. Though if you did make the "motorbike" version, and we lost a few more cells (we're a bit heavier than we'd like), then we might be potential customers. We'd be happy with some way of opening the lid, using those spare vias, and adjusting the voltage externally, even if that voided the warranty.


----------



## Tesseract (Sep 27, 2008)

Brute Force said:


> What sort of connector is being considered? Please say it's an automotive grade weatherproof type and not screw terminals...


I haven't decided on any of the connectors, but the default choice would be the same type of feedthrough barrier strip as used in the Soliton controllers. A slight step up would be a two-piece pluggable/gasketable version of the same made by Phoenix Contact, though all of those I have seen are merely dust-resistant and not water-resistant, per se (e.g. - rated IP51).

Understand that most (read: all) of the weatherproof automotive-grade connectors require a special crimp tool to make the wire terminations, and not using it can compromise the weather-resistance and/or the long-term reliability of the connection. Thus, you the customer would have to either buy or rent the special crimp tool and, of course, use it correctly to install the dc-dc converter.

When I actually start sifting through connectors in earnest I'll toss a few of the contenders up here for your consideration. If nothing else you all might gain an appreciation for the difficulty involved in a task that otherwise seems pretty straightforward and simple.


----------



## Tesseract (Sep 27, 2008)

palmer_md said:


> ...the Renault/Leaf packs that were just sold at EVTV were all ~395v packs...


Is that 395V *actual* or some nebulous, undefined "nominal"?




Jan said:


> I'm wandering if you could connect two converters in series in that case, and parallel the output?


Bad idea, as a switchmode converter acts a constant power load, and so the battery pack voltage will split in inverse proportion to the current drawn by each converter. As long as the two converters are both drawing the same current, no problem, but as soon as one starts to draw just a little bit more current its share of the battery voltage will decrease, causing it to draw even more current, etc., and so on, until the other converter hits its overvoltage shutdown (or blows up).


----------



## Tesseract (Sep 27, 2008)

Tesseract said:


> When I actually start sifting through connectors in earnest I'll toss a few of the contenders up here for your consideration....


First contender for the 12V power terminals are these feedthrough bushings:

VTEWorld - 3/8" 300A

Minuses: I would have to make cables to connect the stud to the pc board. At $12 for a pair they are a lot more expensive than a 4-position barrier strip (in which two terminals are wired in parallel for each output), but, admittedly, the price is not beyond consideration.

Pluses: Rated for way more current than necessary. Weather/touch-resistant boots available for just $2 more. Wire can be crimped with readily available hammer or hydraulic crimpers.

So we probably have a winner here... even as I watch my parts cost creep upwards... Oh well, I knew that was coming.


----------



## Coulomb (Apr 22, 2009)

Tesseract said:


> Bad idea, as a switchmode converter acts a constant power load, and so the battery pack voltage will split in inverse proportion to the current drawn by each converter. ... as soon as one starts to draw just a little bit more current its share of the battery voltage will decrease, causing it to draw even more current, etc., and so on, until the other converter hits its overvoltage shutdown (or blows up).


Oh. That would happen if you just connected the two converters in series, without connecting to the "tap" in the pack. I agree that that is a bad idea. We connect to the centre point of the pack (so each converter is connected across a half-pack), so small differences in current drawn stay small, and the voltage doesn't change appreciably.


----------



## toddshotrods (Feb 10, 2009)

Jan said:


> You'll have a very serious out of balanced pack every day...


Doh!  I was really underestimating how much it might draw, thinking it would be almost insignificant. Thanks.






Tesseract said:


> ...Understand that most (read: all) of the weatherproof automotive-grade connectors require a special crimp tool to make the wire terminations, and not using it can compromise the weather-resistance and/or the long-term reliability of the connection. Thus, you the customer would have to either buy or rent the special crimp tool and, of course, use it correctly to install the dc-dc converter...


Yup, Curt has a drawer full of expensive crimpers - way beyond what the average person would want to spend (per tool) for a _simple_ task.

Most companies that supply products with those connectors also supply a user-end, pre-crimped, wiring harness.


----------



## palmer_md (Jul 22, 2011)

It is a 96 series pack that has each cell fully charged and resting at 4.1volts. Here is the manufacturers site: http://www.eco-aesc-lb.com/en/product/liion_ev/

Here is a user documented voltage curve on discharge of a Leaf. It matches my experience in our Leaf of seeing between 390v and 360v during operation.
http://www.mynissanleaf.com/viewtopic.php?f=31&t=6116&hilit=turtle+dead&start=79


----------



## Tesseract (Sep 27, 2008)

palmer_md said:


> It is a 96 series pack that has each cell fully charged and resting at 4.1volts.


The design as it stands should handle that voltage, though the buck's freewheeling diode might get too hot. Won't know for sure until I build the prototype.


----------



## Batterypoweredtoad (Feb 5, 2008)

Shouldn't it handle a Shiva? I'm in for the donation/purchase when it gets going. Just sold a few things and will earmark some of the cash-just say when.


----------



## Tesseract (Sep 27, 2008)

Batterypoweredtoad said:


> Shouldn't it handle a Shiva?


In a previous post I said I might be able to extend the range depending on how well the prototype performs. More specifically, I need to see how well the die cast aluminum box acts as a heatsink. The problem with increasing the max input without a corresponding increase in the minimum input voltage is that the freewheeling diode runs hotter, as both the conduction losses increase (from having to conduct a higher average current) and the switching losses increase (which are proportional to both current and voltage). The switching loss is the real killer, as it basically goes up with the square of voltage in the FWD, so even a seemingly minor increase of 400V to 425V can result in dramatically higher losses.

This is why switching frequency declines as operating voltage and power level climb. I can run a 700W dc-dc converter at 100-150kHz, but a 300kW Soliton has to be limited to ~8kHz and a 650kW locomotive drive has to be limited to 2kHz.

Now I could do the same thing here - lower the switching frequency - but then I would have to move up to the next larger core for the transformer (I'm already squeezing as much from it as I can) and that would require a bigger enclosure, etc... So this minor change has a cascading effect that results in an outsized increase in price.

As I've said before, I've already given the design of this dc-dc a lot of thought and so I have high confidence in my estimated specs. After I build a prototype I might find that some of my loss estimates are a little conservative and/or that the enclosure acts as better heatsink, and so I might be able to safely increase the input voltage range, but for now consider that spec to be pretty much nailed down.


----------



## Yukon_Shane (Jul 15, 2010)

As a point of discussion on this thread, in my efforts to try and replace my crappy iota dc/dc converter (and before this thread was started) I got a deal on one of the Azure-Dynamic asset auction TDK DC/DC converters.

Recognizing that my battery pack is outside of the voltage range of this TDK unit, I knew it likely wouldn't work for me but I figured for $90 it was worth a try and if it didn't work it could make a decent trophy for a potential future higher voltage project.

I received this unit a couple days ago and noticed that it actually appears to be liquid cooled. Perhaps this isn't a surprise to those of you familiar with OEM DC/DC's but it seemed a bit strange to me.

Tesseract: I suspect you've given this options some thought in addressing heating issues. What are the prose/cons of this water cooled approach? Does it adds significantly to the material costs? Would it allow for significant voltage/current increases to your current design?

For my purposes the specs on your current design are perfect and I think the robust but simple (from a users perspective) design approach is best for a product such as an EV DC/DC converter; for my money I would prefer the unit to have 4 connections and limited/no adjustment. I say keep it simple, the spaghetti wires and strange looking connectors associated with this TDK unit scare the pants off me and I suspect it would take me a month to figure out how to hook it up just to discover that it won't work at voltages below 250V (which I'm already certain is true).

Now that this "baby soliton" product is looking like it will become a reality, I'm quite happy to make a space for this TDK unit on my shop shelf. 

Now we just need to convince you to take on a charger


----------



## Tesseract (Sep 27, 2008)

Yukon_Shane said:


> ...What are the prose/cons of this water cooled approach? Does it adds significantly to the material costs? Would it allow for significant voltage/current increases to your current design?


The semiconductor losses in this design are not terribly high, it's just that they are produced by relatively small parts (ie - TO-247 or TO-220 packages) which are then depending on the (as yet unknown) thermal properties of an off-the-shelf die cast aluminum enclosure to keep them cool. Adding liquid cooling to a custom enclosure would be trivial (it adds almost no cost to the Soliton controllers, for example) but trying to incorporate a cold-plate into off-the-shelf enclosure would be nightmarish. I would either have to cut a large window for the semiconductors inside the box to attach to the cold plate outside of it, or I would have to figure out a way to seal the hole for the hose fittings as they exit the box. Either way, a lot of assembly labor and the potential for reliability problems. Also, liquid cooling does vastly increase the amount of a power a given semiconductor package can handle, but *only* if you monitor that device's temperature and do something to limit the power quickly should the cooling system fail. I will be monitoring the hottest device(s) (probably the output rectifiers) to protect against over-temp, but this protection doesn't have to be terribly quick nor accurate with a purely passively-cooled design.



Yukon_Shane said:


> Now we just need to convince you to take on a charger


If the dc-dc goes well I'll reconsider it...


----------



## Joey (Oct 12, 2007)

I'm extremely excited to see this potentially come back to life.



Tesseract said:


> This is the central question, and the answer is simply that my converter will be designed for use in an EV. Either that is immediately worth the $150 premium to you, or you can effectively pay ~$550 for it later on... after having to replace the $200 Mean Well that, well, meant well, but couldn't quite handle the often-hostile EV environment.
> 
> 1. The topology I've chosen (buck current-fed full bridge) is uniquely suited to handling wild swings in pack voltage. The typical commercial power supply is ill-equipped to handle this because it either uses a voltage-selector switch and so can only run over the range of around 275-375VDC, or it uses a PFC stage to cover the entire AC mains range but then suffers from extremely slow transient response because the loop bandwidth of the PFC stage needs to be well under the line frequency to meet the IEC power factor and distortion specs.
> 
> ...


All of these issues would lead me to replace the meanwell supply that has been working well in my car for the last 9 months - especially the fan noise and the parasitic load. I will be watching this thread so that I can be one of the first to sign up to support for this project. 



Tesseract said:


> I can live with that. I don't think I am going to accommodate a 3s LiPo pack, though - firstly, I don't see too many people crazy enough to go that route and secondly, headlights are noticeably dimmer if the "at battery" voltage is 12.6V. So two voltage choices, 13.6V for LFP and 14.0V for Pb, but with 14.0V the default option, because a top-balanced 4s LFP pack would be perfectly happy with that voltage.
> 
> That said, I have been looking at enclosures once again and found this ugly sonuvabiscuit which has an integrated silicone gasket to achieve an IP67 rating (essentially waterproof): Bud IPS-3935. Mounting ears are available, too, for an extra $4.10.





Tesseract said:


> Okay, I'm not going to put in a trimpot just so you can tweak amplifiers, but I will put in a couple of vias on the board to make it easy to wire in an external variable resistor. However, note that I will have to limit the adjustment range to not interfere too much with the stability of the control loop. And don't ask for more than 14.0V because then I have to change the number of turns on the transformer or raise the minimum voltage, and that would annoy me greatly...


Finding credible specs for float charge voltage on lithium cells, (or equivalently the open circuit voltage vs. state of charge) is proving difficult. It seems that 10 Ah Headway HW 38120L/S cells will be fine with <= 3.6 V, but I can't find anything but opinions for other cells. The resting voltage on my CALB CA traction pack 24 hours after charge is around 3.35 V/cell, and I suspect I'm slightly under charging. Float charging needs to be done at a lower voltage than the CC/CV profile that most use for the traction pack. Having a standard config set at 14 volts, and those vias to select between 13.4 and 14 volt output (I personally would solder in a fixed value resistor after finding the correct value with a pot) would be very accommodating for all but the last 2% of users that take up 90% of your support time.



Tesseract said:


> First contender for the 12V power terminals are these feedthrough bushings:
> 
> VTEWorld - 3/8" 300A
> 
> ...


I would be more than happy with those connectors. Something to consider might be using a cable gland for the enclosure feed through and then connecting the wires to a terminal strip inside the enclosure. Pros: IP-68, no special crimpers. Not too expensive Cons: requires more enclosure space, you need to open the enclosure to make the connection, limited diameter range of the cable that can be used to hook up the DC-DC, might have to crimp ring terminals after feeding the cable through the gland.

If this goes well and you decide to look at charger, I would be interested to know your thoughts on a DC quick charger. Probably a topic for a different thread.


----------



## Tesseract (Sep 27, 2008)

Joey said:


> ...Something to consider might be using a cable gland for the enclosure feed through and then connecting the wires to a terminal strip inside the enclosure.....


Excellent suggestion! I'm a little embarrassed, actually, that I didn't think of this myself... Cable glands would be less expensive, don't require interconnect cables to go from the enclosure to the board, and can still achieve an IP65-67 rating for dust/water resistance. Having to open the case to make the connections isn't a dealbreaker (as long as an o-ring is used for sealing!) so the only potential negative to cable glands is that the allowed wire diameter is limited, but given that the wire diameter needs to be a minimum size to handle the output current, that's not too much of an issue. 



Joey said:


> If this goes well and you decide to look at charger, I would be interested to know your thoughts on a DC quick charger. Probably a topic for a different thread.


Sure, start a new thread and I'll chime in. "ChargedEVs" magazine asked me to write an article about level 3 charging and, well, I haven't gotten around to it yet (next up will probably be an article on power semiconductor technology).


----------



## Duncan (Dec 8, 2008)

_Finding credible specs for float charge voltage on lithium cells, (or equivalently the open circuit voltage vs. state of charge) is proving difficult. It seems that 10 Ah Headway HW 38120L/S cells will be fine with <= 3.6 V, but I can't find anything but opinions for other cells. The resting voltage on my CALB CA traction pack 24 hours after charge is around 3.35 V/cell, and I suspect I'm slightly under charging. Float charging needs to be done at a lower voltage than the CC/CV profile that most use for the traction pack. Having a standard config set at 14 volts, and those vias to select between 13.4 and 14 volt output (I personally would solder in a fixed value resistor after finding the correct value with a pot) would be very accommodating for all but the last 2% of users that take up 90% of your support time.

_Why is this so critical?
If you are using 4 Lithium cells as an auxiliary battery you should be aiming for somewhere near the middle of the charge
Anything between 40% and 80% charged should do
The Auxiliary battery is only to cover spikes in demand and to give back-up for emergencies
You don't want it to be fully charged as that will reduce its life


----------



## gunnarhs (Apr 24, 2012)

Joey said:


> I would be more than happy with those connectors. Something to consider might be using a cable gland for the enclosure feed through and then connecting the wires to a terminal strip inside the enclosure. Pros: IP-68, no special crimpers. Not too expensive Cons: requires more enclosure space, you need to open the enclosure to make the connection, limited diameter range of the cable that can be used to hook up the DC-DC, might have to crimp ring terminals after feeding the cable through the gland.


I totally support this idea, this is much closer to the way I would do it coming from the electric background.
I tend to disagree with some of my fellows in the automobile branch about electric enclosures, safety etc. The problem I see with these crimping tools is that they are often not commonly standardized (require special connectors etc.) and that in case of adjustment, which often is necessary when building a prototype car, you end up changing the connectors AND cables very often. Meaning these tools are not suitable when constantly changing the environment which is a big part of DIY. A cable gland is a much more flexible solution.


----------



## dougingraham (Jul 26, 2011)

Duncan said:


> _Finding credible specs for float charge voltage on lithium cells, (or equivalently the open circuit voltage vs. state of charge) is proving difficult. It seems that 10 Ah Headway HW 38120L/S cells will be fine with <= 3.6 V, but I can't find anything but opinions for other cells. The resting voltage on my CALB CA traction pack 24 hours after charge is around 3.35 V/cell, and I suspect I'm slightly under charging. Float charging needs to be done at a lower voltage than the CC/CV profile that most use for the traction pack. Having a standard config set at 14 volts, and those vias to select between 13.4 and 14 volt output (I personally would solder in a fixed value resistor after finding the correct value with a pot) would be very accommodating for all but the last 2% of users that take up 90% of your support time.
> 
> _Why is this so critical?
> If you are using 4 Lithium cells as an auxiliary battery you should be aiming for somewhere near the middle of the charge
> ...


A123 on their spec sheet for the 26650 cells indicated 3.45 volts was the correct float voltage. This eventually results in a fully charged cell. I am floating my pack of these cells to 3.40 volts so they never actually quite get fully charged.

One reason to fully charge your pack is in case the DC-DC fails or you have a total failure of the traction system. This would allow you to operate your hazard lights for a period of time. I get several hours of operation on my 8AH buffer battery. My own experiments with leaving LiFePO4 cells fully charged for months on end is that they are not damaged by this. I don't know what the result is if you leave the cells floating above 3.4 volts for long periods. I do know that this 2.5 year old pack I built as a buffer battery tested the same at the two year mark as it did when new. And it has been floated at 3.4 volts per cell for its whole life.

I believe John Hardy is doing an overvoltage float test to see what happens long term. I look forward to those results.


----------



## crackerjackz (Jun 26, 2009)

hey tesserect . may be worth you looking at these enclosures ... http://www.ebay.com/itm/Aluminum-Pr...728?pt=LH_DefaultDomain_0&hash=item35d2ca8e38

not sealed as is but nothing urethane and sealant wont fix ... plus it would help keep parts cool with the fins ....


----------



## Joey (Oct 12, 2007)

Duncan said:


> _.
> 
> _Why is this so critical?
> If you are using 4 Lithium cells as an auxiliary battery you should be aiming for somewhere near the middle of the charge
> ...


I agree, you probably don't want to be fully charged in a float situation. My thought was that 13.6 volts might be too high for some cells, and I was having trouble finding the recommended float voltages posted online. 

I found my user manual that came with the Calb CA cells and it calls for a maximum float voltage of 3.4 volts per cell. 3.4 x 4 cells = 13.6 V. To avoid the maximum, 13.4 volts would seem like a good setting. I would be more likely to use Headway cells (more reasonable size for my application), and the spec sheet says 3.6 volts/cell max for float. I'm not sure how low the voltage can go, but having vias on the board to allow flexibility for a range of cells sounds like a very good solution to me.


----------



## Tesseract (Sep 27, 2008)

crackerjackz said:


> hey tesserect . may be worth you looking at these enclosures ... http://www.ebay.com/itm/Aluminum-Pr...728?pt=LH_DefaultDomain_0&hash=item35d2ca8e38
> ...


Good find. The only possible problem (besides having to manually seal the box) is that the side walls looked curved on the inside, which would make it impossible to use them as a heatsink. So, I asked the seller if the sides are, indeed, curved - if not then I'll buy a couple to check them out.




Joey said:


> ...My thought was that 13.6 volts might be too high for some cells, and I was having trouble finding the recommended float voltages posted online.
> 
> I found my user manual that came with the Calb CA cells and it calls for a maximum float voltage of 3.4 volts per cell. 3.4 x 4 cells = 13.6 V. To avoid the maximum, 13.4 volts would seem like a good setting.


I already decided on 13.6V and 14.0V as the two output voltage settings 13 days ago (see post 41). Needless to say, this thing will never get designed - much less built - if I have to keep revisiting decisions that were made weeks or months ago.

Besides, you seem to be forgetting two things: 1) there will be some IR (voltage) drop between the dc-dc and battery unless the current is really low; 2) the dc-dc doesn't run 24/7 - ie, it only supplies power to the 12V system when the key is on. Thus, there is little chance of overcharging a 4s LFP battery at 14.0V (3.5vpc), much less at 13.6V (3.4vpc). In fact, undercharging is the more likely outcome, with a concomitant loss of usable capacity.


----------



## Joey (Oct 12, 2007)

I must have misunderstood this comment in post 56:




Tesseract said:


> Okay, I'm not going to put in a trimpot just so you can tweak amplifiers, but I will put in a couple of vias on the board to make it easy to wire in an external variable resistor. However, note that I will have to limit the adjustment range to not interfere too much with the stability of the control loop. And don't ask for more than 14.0V because then I have to change the number of turns on the transformer or raise the minimum voltage, and that would annoy me greatly...


I guess I'm being too conservative, given your points, but given the trade off - possible fire vs loss of useable capacity. It is possible someone forgets to turn the ignition off and leaves the DC-DC on for an extended period. I'm not sure if the on/off switch function can fail on. Simple solution: use the cells with a 3.6 volt float spec.

I'm not trying to stir things up. When you open your design proccess for feedback, we can sometimes get carried away. Continue on...


----------



## Tesseract (Sep 27, 2008)

Joey said:


> I must have misunderstood this comment in post 56:


You perhaps misunderstood the scope of said comment - my adding vias to satisfy one person's weird/unusual request should not have been interpreted as a more general approval to muck around with the output voltage. 



Joey said:


> I guess I'm being too conservative, given your points, but given the trade off - possible fire vs loss of useable capacity. It is possible someone forgets to turn the ignition off and leaves the DC-DC on for an extended period. I'm not sure if the on/off switch function can fail on. Simple solution: use the cells with a 3.6 volt float spec.
> 
> I'm not trying to stir things up. When you open your design proccess for feedback, we can sometimes get carried away. Continue on...


First off, applying 13.6v to a 4s LFP pack will not result in it catching on fire. And while 14.0V *may* result in one cell being slightly overcharged ...eventually... that is still a relatively low probability event requiring both that the DC-DC be left on for many hours and that the battery be bottom-balanced as well. Otherwise, each cell at 14.0V will asymptotically approach 3.5V and that is 0.1V less than what is recommended for the CV part of the charge cycle on pretty much every LFP cell out there, Headway excepted, apparently (then again, 2-4% of Headway cells still show up as DOA, so maybe we shouldn't place so much faith in their datasheets, n'est-ce pas?)

As for what can fail... Everything!

That said, the "on-off" switch inside the dc-dc isn't really a switch, rather, I am just separating the line that supplies power to the control circuit, rather than supplying the control circuit directly from either the HV side (which spans too wide a voltage range) or the LV side, which would draw some power all the time, even when "shutdown". It's a very simple solution to the quiescent current problem, but one which I feel is quite elegant, and I am all for elegant solutions.

Finally, I'm not really looking for criticism of my design so much as soliciting comments on what features are needed - and *why* - as well as help with funding the development and/or production of the DC-DC via Kickstarter. All of you arguing about whether to charge your dinky little 4s LFP battery (and which probably cost all of $50) at 13.4V or 13.6V are giving me a headache...


----------



## Tesseract (Sep 27, 2008)

In other news, I received a couple of the sample enclosures I ordered from China today... let's just say they make that hideous Bud enclosure look pretty damn good. Oh well, that's why you buy samples!


----------



## gunnarhs (Apr 24, 2012)

Tesseract said:


> In other news, I received a couple of the sample enclosures I ordered from China today... let's just say they make that hideous Bud enclosure look pretty damn good. Oh well, that's why you buy samples!


 Ok good, any other updates on the kickstarting financing ?


----------



## JRP3 (Mar 7, 2008)

Tesseract said:


> Besides, you seem to be forgetting two things: 1) there will be some IR (voltage) drop between the dc-dc and battery unless the current is really low;


What sort of voltage drop during operation are you expecting? With my current setup, Meanwell 600 watt, if I set the voltage below 14V or so the contactor for my heating system won't engage. Unfortunately anything above 13.8V made my EV Display keep resetting, but I solved that with 2 silicon diodes in series on the 12V input for the display.


----------



## Tesseract (Sep 27, 2008)

gunnarhs said:


> Ok good, any other updates on the kickstarting financing ?


I'm leaning towards using the Kickstarter campaign to fund a limited production run of the converters, rather than both the development of the converters and their production. In other words, I will fund the development of the prototype out of pocket. That was something I really wanted to avoid doing, but it seems that a Kickstarter campaign is much more likely to succeed if the goal is just to mass produce something that already works (and which one already knows the cost to build it - at least in prototype quantities).

So that means I am or will be getting quotes for the custom magnetics, building the bill of materials, designing the board, etc. first, then debugging/revising the prototype. 

I also dusted off a limited liability company I incorporated a few years ago along with the business bank account that has all but sat dormant with a whopping big $100 in it. I need to set up accounts linked to said company with Amazon payments and PayPal, have a website made, etc.

In the meantime, I also have work to do on the locomotive drive system for Evnetics. So it will likely be a few more weeks before I finish the first revision of the board and then a few more weeks before I'll be ready to launch the Kickstarter campaign.


----------



## Tesseract (Sep 27, 2008)

JRP3 said:


> What sort of voltage drop during operation are you expecting?...


That depends on three things that are outside of my control: 1) the cable resistance; 2) the current demanded from the converter; 3) the cleanliness of the interconnects.


----------



## JRP3 (Mar 7, 2008)

Let's say good connections and short cables, at max current draw. I assume you have an idea how stable the voltage will be under load.


----------



## Tesseract (Sep 27, 2008)

JRP3 said:


> Let's say good connections and short cables, at max current draw. I assume you have an idea how stable the voltage will be under load.


Figure on a minimum circuit resistance on the output side of 2mΩ, with 4mΩ being more likely. At 50A that will be 0.1V to 0.2V of drop.


----------



## crackerjackz (Jun 26, 2009)

Tesseract said:


> That depends on three things that are outside of my control: 1) the length of the cables; 2) the current demanded from the converter; 3) the cleanliness of the interconnects.



You forgot the size of the wiring ...


----------



## Tesseract (Sep 27, 2008)

crackerjackz said:


> You forgot the size of the wiring ...


Oh-ho... look who's correcting me for a change. Yes I did forget the size of the wiring... along with a few other things of lesser importance. So I reworded #1 to lump all of that under "cable resistance".


----------



## crackerjackz (Jun 26, 2009)

Tesseract said:


> Oh-ho... look who's correcting me for a change. Yes I did forget the size of the wiring... along with a few other things of lesser importance. So I reworded #1 to lump all of that under "cable resistance".



I didn't think of it as correcting you ... More like adding information where i can . This is after all what this website is about  ... From experience wiring size has a huge importance to the final end voltage under load . Obviously as the distance increases in wiring so should its size to retain proper conductivity ... You know this im sure . But many dont .


----------



## Tesseract (Sep 27, 2008)

crackerjackz said:


> From experience wiring size has a huge importance to the final end voltage under load...


Yep - wiring resistance is directly proportional to length, and inversely proportional to area (or the square of diameter, if you prefer). I mentioned the length factor in my original reply, but failed to mention the area factor, so you were entirely correct to call me out on it. I didn't take it personally - it was an oversight on my part and fixing it was the right thing to do. I may be a royal a-hole, but I am an ethical royal a-hole.


----------



## Yukon_Shane (Jul 15, 2010)

Any updates?

My Iota is making a funny noise these days and is going to die any second now. Don't make me have to buy one of those horrible Meanwell monstrosities.


----------



## Tesseract (Sep 27, 2008)

Yukon_Shane said:


> Any updates?
> 
> My Iota is making a funny noise these days and is going to die any second now. Don't make me have to buy one of those horrible Meanwell monstrosities.


I've been working on making some final tweaks to the locomotive drive system after it was finally tested in a working locomotive so I've set this project aside for now. I might be able to resume working on it in a few more weeks, but be warned that the lead time on the custom transformer and magnetics is either 8 weeks *or* very expensive, and since I am self-funding the prototype (based on feedback here vis-a-vis Kickstarter) I am disinclined to spend lots of my money just to get a product to market faster.


----------



## RIPPERTON (Jan 26, 2010)

Lets contemplate this for a possibly very cheap DCDC system

http://www.diyelectriccar.com/forums/showthread.php/12v-regen-system-96955.html


----------



## Yukon_Shane (Jul 15, 2010)

I'm going to change my forum name to "the nag" soon.

Any updates Tesseract? 

My dc/dc has finally died confirming my suspicion that this is the weakest part of my build (and likely most other peoples on this forum). If you're product is on it's way to production I'll wait but if it's looking like it might be awhile I'll have to sort out an alternative.

cheers,


----------



## steelneck (Apr 19, 2013)

Tesseract, you can count me in as a buyer of your DC/DC when it is ready. For now i am using an alternator direct drive from the tailshaft, but it is an old and very used one..


----------



## Tesseract (Sep 27, 2008)

Yukon_Shane said:


> I'm going to change my forum name to "the nag" soon.
> 
> Any updates Tesseract? ...


Nope, I haven't done a lick of work on this in months, mostly because I was still working on the locomotive drive system up until last weekend. 

Also, isn't Jack Rickard trying to get people to hack OEM EV components so they can be used outside of their native environment? I expect that if someone got the dc-dc from a Leaf to work outside of a Leaf it would greatly reduce demand for my dc-dc converter...


----------



## steelneck (Apr 19, 2013)

I think you are downplaying your self now.. Think of what you are comparing here, a dirty hack of something (that could be hard to come over in the first place) to get it to work outside of its native environment, and a much more generic thing made to work reliably in just about whatever custom built car.

EV-conversions are custom cars, think of all the things specially built for custom cars, or even all stores both online and physical selling custom parts. Yes, for now the DIY EV scene is not big, but it is getting bigger. You have taken a corner of this market with your Soliton controller, you could also do it regarding DC/DC, and that is a larger market than hi perf DC controllers (our AC friends also need DC/DC). Another area missing in the market is a simple "plug n play" heater control made for custom automotive use.


----------



## rwaudio (May 22, 2008)

Tesseract said:


> Nope, I haven't done a lick of work on this in months, mostly because I was still working on the locomotive drive system up until last weekend.
> 
> Also, isn't Jack Rickard trying to get people to hack OEM EV components so they can be used outside of their native environment? I expect that if someone got the dc-dc from a Leaf to work outside of a Leaf it would greatly reduce demand for my dc-dc converter...


More than anything that would depend on the voltage range, and does it require a CAN signal to operate. The first could be a deal breaker to many builds and if the 2nd adds 100's of dollars to the installed cost it's a much less attractive option.


----------



## Yukon_Shane (Jul 15, 2010)

Tesseract said:


> Nope, I haven't done a lick of work on this in months, mostly because I was still working on the locomotive drive system up until last weekend.
> 
> Also, isn't Jack Rickard trying to get people to hack OEM EV components so they can be used outside of their native environment? I expect that if someone got the dc-dc from a Leaf to work outside of a Leaf it would greatly reduce demand for my dc-dc converter...


Sounds like this project is looking less likely, that's too bad.

It's interesting to speculate how Jack Rickard's work is effecting the DIY EV market. From my perspective it's fun to watch these experiments but I haven't seen/heard anything that would motivate me to consider purchasing any of his "adapted" products. I suspect many of these efforts are a direct result of a lack of good quality equipment such as the one you've proposed here (ie. if the community had a good quality, reasonably priced DC/DC no-one would be bothered trying to figure out how to make a Leaf DC/DC work for them).

In watching his show I often get the impression that Jack has cultivated a small group of very loyal fans that buy from him exclusively ("Jack Nation") but don't necessarily represent the larger DIY EV community. In my opinion his focus on somewhat rare and expensive AC and OEM equipment is making his show increasingly irrelevant to the average person who may be interested in converting their vehicle to electric.

I'd say there is still going to be a market for a well built, simple, reliable, DC/DC converter designed for the DIY EV market. Not just for new builds but also for all the folks like me that installed crappy converters a few years ago and now they're all starting to die. We're probably the real market for this product because anyone who's had to replace something once is likely willing to pay a bit extra for a better product that they won't have to replace again. A quick run through the various EV conversion online stores offerings gives you an idea as to the gap that exists. Most of these stores are suggesting a noname DC/DC convert that looks like it was ripped off the back of some server rack or something.

All that being said I can't blame you for being reluctant to dive into this project. I expect it would be alot of work for relatively small profit.


----------



## samwichse (Jan 28, 2012)

The DC DC from a Honda Insight is cheap, rated at 70A, works from 80-220V, and requires no hacking to get working.

In all my years on the insightcentral forum, I've never heard of a single case of one failing. Peter, the forums resident engineer-at-large, has called the design "a work of art."

http://www.insightcentral.net/forum...s/21025-dc-dc-inverter-needed-experiment.html

Usually on eBay around $160, but you so around you can get them cheaper.
http://m.ebay.com/itm/321455698526?nav=SEARCH


----------



## 67BGTEV (Nov 1, 2013)

Thanks Sam for sharing this info and the InsightCentral URL. Went through it and bought the Converter. I hope it works out for me..



samwichse said:


> The DC DC from a Honda Insight is cheap, rated at 70A, works from 80-220V, and requires no hacking to get working.
> 
> In all my years on the insightcentral forum, I've never heard of a single case of one failing. Peter, the forums resident engineer-at-large, has called the design "a work of art."
> 
> ...


----------



## Yukon_Shane (Jul 15, 2010)

samwichse said:


> The DC DC from a Honda Insight is cheap, rated at 70A, works from 80-220V, and requires no hacking to get working.
> 
> In all my years on the insightcentral forum, I've never heard of a single case of one failing. Peter, the forums resident engineer-at-large, has called the design "a work of art."
> 
> ...


Interesting that I haven't seen anyone post on this here before. 

thanks.


----------



## Elegancec (May 23, 2012)

Im also searching for a 400V DC DC converter.
My second Meanwell PSP 600 -13.5V died now and the seller is not present anymore, so no warranty left.
It died while switching on again the 260V side and the 12V side was still connected.
Has anyone have an idea what it could be? Nothing obvious what I could see so far.
But a more reliable solution would be great.


----------



## 67BGTEV (Nov 1, 2013)

67BGTEV said:


> Thanks Sam for sharing this info and the InsightCentral URL. Went through it and bought the Converter. I hope it works out for me..


Sam, 
Thanks again for sharing the details about the Insight DC-DC Converter. I got the shipment last week and bench tested it yesterday. It works well. I'm planning to integrate into my BGTEV drive next week.


----------



## samwichse (Jan 28, 2012)

No problemo, glad I could contribute .


----------



## bfuqua (Sep 6, 2012)

Tesserect - 

it appears from your last post that this project is at least on hold. I read this string from front to back today and was getting very encouraged about the possibilities as I consider my DC-DC converter to be a weak link as well.

I do have an additional request for information and folks on this thread might be able to point me in the right direction. Like Tesserect I live in a hurricane prone area. I keep thinking I have this huge power pack fully charged and it would run my refrigerator and some lights for days.... I just need to tap into it in emergencies (well, also at the tailgating parties before the football games - of course that is an emergency). Folks keep saying to get a converter to 12V and then an inverter to 120 VAC. This really sounds inefficient to me and it seams there would be a market for something like this. Bill


----------



## JRP3 (Mar 7, 2008)

A company was producing them but I'm not sure if they still do.

http://electricbluemotors.com/blueflash120.html


----------



## bwjunkie (Jul 31, 2013)

JRP3 said:


> A company was producing them but I'm not sure if they still do.
> 
> http://electricbluemotors.com/blueflash120.html


Hah, that article mentions accurately running a turntable. So in a hurricane emergency you could still listen to your vinyl records! I can appreciate that.


----------



## Tesseract (Sep 27, 2008)

bfuqua said:


> ...
> it appears from your last post that this project is at least on hold. I read this string from front to back today and was getting very encouraged about the possibilities as I consider my DC-DC converter to be a weak link as well.


It was on hold while I did some more work for the locomotive drive system but when samwichse posted about the Honda Insight dc-dc converter that can be had from ebay/junkyards for $160 or less that basically killed any incentive on my part to resume working on this. I don't blame y'all for re-purposing used OEM components, but realize that soon that might be all you have to choose from.



bfuqua said:


> ...I keep thinking I have this huge power pack fully charged and it would run my refrigerator and some lights for days...


Yep, I also think that a 60Hz "static" inverter that can work on a wide range of DC input voltage would have broad appeal, especially if it can be connected to a Leaf's battery pack without voiding the warranty.


----------



## palmer_md (Jul 22, 2011)

Tesseract said:


> It was on hold while I did some more work for the locomotive drive system but when samwichse posted about the Honda Insight dc-dc converter that can be had from ebay/junkyards for $160 or less that basically killed any incentive on my part to resume working on this. I don't blame y'all for re-purposing used OEM components, but realize that soon that might be all you have to choose from.
> 
> ...


The Honda unit is fine for those who are running low voltage like the curtis controllers, but with a maximum of 180v dc input, it is a non starter for those of us running higher voltage.

I fully understand your hesitation to enter this market since the Honda unit does offer a way out for about half your potential market.

I just want to say thank you for all the work you have done for this community in both the Evnetics line of controllers as well as just answering general questions around here. It is very nice to have access to someone of your talents. That goes for your two partners at EVnetics as well. 

I for one am still looking for a good DC-DC solution, so I guess my quest moves on.


----------



## samwichse (Jan 28, 2012)

Tesseract said:


> It was on hold while I did some more work for the locomotive drive system but when samwichse posted about the Honda Insight dc-dc converter that can be had from ebay/junkyards for $160 or less that basically killed any incentive on my part to resume working on this.


What have I done???

I didn't mean to kill a great project, just thought people needing a stop gap solution could find one.

Keep in mind worldwide Insight production was only about 18k total... not that many cars, and it's been out of production for 9 years now.


----------



## EV-propulsion.com (Jun 1, 2009)

Tess,
I hope you would reconsider, most of my customers builds are for quality parts, preferable "bolt in, plug and play". The builders are investing in a later model car, or a restoration, looking to make a clean, reliable vehicle and are looking for the best available (within reason of course), and not looking to scrounge scrapyards for parts as good as they may be. They generally don't want to piece together a bunch of parts that may not work well together, which is what is happening with the available DCDC converters being used now-it definitely is the weak link.
I would think at least 80% (probably more) of the soliton customers (and you know how many of those sold) would definitely buy one of your converters if available-I really don't see a problem with being a little higher cost like you are considering, if having a product like the soliton is the end product. We sold a bunch of solitons, I think almost all would have bought a DCDC from the same mfg. - after all almost all did purchase the soliton throttle with their controller - they could have made something else work for less cash, but didn't.
Yes there will always be the low cost builds (and there is nothing wrong with that-it generally shows inginuity on the part of the builder to do a low cost build) but the market I see is headed in the opposite direction- using AC motors, etc now. 
So I say build it!
Mike
EV-propulsion llc


----------



## steelneck (Apr 19, 2013)

EV-propulsion.com said:


> ... most of my customers builds are for quality parts, preferable "bolt in, plug and play". The builders are investing in a later model car, or a restoration, looking to make a clean, reliable vehicle and are looking for the best available (within reason of course), and not looking to scrounge scrapyards for parts as good as they may be. They generally don't want to piece together a bunch of parts that may not work well together,


Yes, many of us are the same people that built various custom cars some years ago. Today we have just chosen a bit different propulsion system. It is just a matter of time until some of the classic firms providing custom parts start to also have some EV-custom parts.

Think of classic custom part brands like Edelbrock, MSD, Isky cams, Hooker Headers and so on. Among us doing EV-conversions, today we can add Evnetics and a few other brands.


----------



## Tesseract (Sep 27, 2008)

Thanks for the positive comments but there is no avoiding the fact that the Honda DC-DC covers the vast majority of DIY EV applications and there are more OEM EVs and PHEVs coming, so I can expect more competition in that respect, not less.

That said, there is no way I can make a DC-DC that is competitive with one from a Honda Insight, or a Nissan Leaf, or whatever OEM hybrid/BEV comes down the pike, but if I take a totally different (and altogether much more quotidian) design approach I might be able to widen the input range slightly, increase the output power some, and still reduce the parts cost.

That said, understand that this is what I do for a living and so I expect to make a reasonable profit on anything I produce. In this particular case, I need to make at least $100 per unit for it to be worth my time, and even that presupposes the boards are assembled by someone besides me. And for this to be remotely palatable on the retail level it needs to sell for less than my initial estimated price of $350-$400; more like $300 or less, which means I need to get the manufactured cost below $200. That's going to be tough, but perhaps not impossible.


----------



## steelneck (Apr 19, 2013)

Tesseract said:


> Thanks for the positive comments but there is no avoiding the fact that the Honda DC-DC covers the vast majority of DIY EV applications and there are more OEM EVs and PHEVs coming, so I can expect more competition in that respect, not less.


I do not think Edelbrock or similar makers of custom parts see them self as competitors to yunkyards.. Your worst competitor is probably old alternators, but if i had the choice, i would rather buy a reliable DC/DC made for custom cars if that option actually did exist. You have the chance of taking a corner of this market, just as you have done with the Solitons, right now there is a window of opportunity for a product in some demand that does not exist.


----------



## JRP3 (Mar 7, 2008)

The problem is the DIY market is tiny at this point, (contrary to what Jack Rickard may claim), not the huge, established ICE aftermarket that Edelbrock sells into.


----------



## steelneck (Apr 19, 2013)

JRP3 said:


> The problem is the DIY market is tiny at this point, (contrary to what Jack Rickard may claim), not the huge, established ICE aftermarket that Edelbrock sells into.


Yes that's right. But how did the market for custom parts look like in the fourties when Edelbrock began its long journey to the old respected name it is today. Edelbrock may be an extreme example, but i think you get my point. There are lots of more recent examples regarding more specialized parts, like MSD or others making electronics for custom cars. I know, Tess may have to take a quite hefty price initially, but he will be No1 at least for a while, and that while is very important regarding his future spot in the market.

I think the first paragraph on the Edelbrock history page describe it quite well, a short cite of it:



> In the early days of the automotive performance industry, you either ran what was available, or you fabricated something you thought met your needs. Such needs were the building blocks of this industry,


Today we can see the exact same situation regarding parts for custom built EVs.


----------



## JRP3 (Mar 7, 2008)

The problem is the EV world is closer to the 20's now than the 40's. We don't have 20+ years of volume OEM production behind us to build large a aftermarket upon. Not that I'm trying to talk Tess out of doing a DC/DC, just trying to have a realistic look at the market.

Off topic, but regarding the DC to AC pack inverter discussed previously, I was wondering if any solar panel inverters run at higher DC voltages than 48V?


----------



## steelneck (Apr 19, 2013)

JRP3 said:


> We don't have 20+ years of volume OEM production behind us to build large a aftermarket upon.


Thats right, we have only 80 years OEM production of cars to convert. I think that the custom EV-market will look quite different 5-10 years from now. Cars like the Zombie, Zombie222, that green BMW in Croatia(?) and other hi perf EV conversions will have a huge impact on the EV-custom part market (or even HotRod if you want).

Though it will never be world wide big as in OEM production, we are not talking about mega corporations here. Custom car builders, EVs or ICE, are quite few compared to those selling to the passive consumerist Joe Average.


----------



## JRP3 (Mar 7, 2008)

My point was more that the demand for the EV portion is still in the infant stages. I think the sales volumes in the DIY EV market bears that out.


----------



## EV-propulsion.com (Jun 1, 2009)

Tesseract said:


> And for this to be remotely palatable on the retail level it needs to sell for less than my initial estimated price of $350-$400; more like $300 or less, which means I need to get the manufactured cost below $200. That's going to be tough, but perhaps not impossible.


I still don't see a problem with a reliable product at $400. If wiring is simple and doesn't have to be a kludge like some of the available units wind up being, it's well worth it. We have had to relay in other maker's units fan controls, on off circuits, input wiring, etc - They just don't make for a clean installation, not to mention reliability....And, after all, the soliton cost much more than a Kelly or a Curtis, and no one really buys _them_ anymore... so you don't _have_ _to_ compete on price always...
Mike


----------



## sholland (Jan 16, 2012)

I would love to have DC-DC with the same quality and look of the Soliton... and I would pay a premium for it. But I know that I'd be getting what I paid for, rather than now constantly worrying if the industrial DC-DC I'm using will last...


----------



## Tesseract (Sep 27, 2008)

It is important to understand that the thermal and environmental performance of the DC-DC, as well as its overall cost, are all heavily dependent on the enclosure. Asking me to put the DC-DC into a sexy, Soliton-esque enclosure will easily add $150 to the manufactured cost and I really feel that will make the retail cost wholly unpalatable. Also, it is much more difficult to pin down the real cost of a custom-milled enclosure, and as I said in the thread from 2 years ago, it's one thing to be off by $100 for the enclosure cost of a $3000 Soliton1; quite another for a $350 DC-DC...


----------



## TheSGC (Nov 15, 2007)

Tesseract said:


> Yep, I also think that a 60Hz "static" inverter that can work on a wide range of DC input voltage would have broad appeal, especially if it can be connected to a Leaf's battery pack without voiding the warranty.


If I could have a DC/DC converter for my EV (13.6v 50a+), with a 60 Hz 110v 2kW+ output I'd pay $1k for that any day... Then I wouldn't need a generator, and it would act has "jump start" for charging another EV if they ran out of power.


----------



## gunnarhs (Apr 24, 2012)

Same here just to confirm my ongoing and not dying interest for this project.


----------



## JRP3 (Mar 7, 2008)

Tesseract said:


> Asking me to put the DC-DC into a sexy, Soliton-esque enclosure will easily add $150 to the manufactured cost and I really feel that will make the retail cost wholly unpalatable.


I'd say you do the basic enclosure since most people don't spend much time looking at their DC/DC. For the ones who do, they can dress it up as they wish.


----------



## sholland (Jan 16, 2012)

JRP3 said:


> I'd say you do the basic enclosure since most people don't spend much time looking at their DC/DC. For the ones who do, they can dress it up as they wish.


I agree with this, and I suppose I should clarify my previous request... My thinking is that whatever you provide will at least have an enclosure that can handle the elements, required thermal handling and has easy connections. It doesn't have to be as fancy as the Soliton1, but I'm sure a product from you will have what it requires. That was the point I was trying to convey...


----------



## steelneck (Apr 19, 2013)

Would a box like this suit your needs?

http://www.electrokit.com/g1201-aluminiumlada-gjuten-tat-171x121x55mm.42596

It is casted aluminum and watertight, 6 countesinked hex screw lid with o-ring seal. The price on the page, 229 SEK is with tax in Sweden, i guess the shop get it for something like 17-20 US dollar.

Update. As for connections, just have wires going out of the box through proper seals. Locktite the screws if you do not want people to poke inside without breaking warranty (the foam rubber o-ring will melt if someone try to heat the locktite to be able to unscrew).


----------



## Tesseract (Sep 27, 2008)

steelneck said:


> Would a box like this suit your needs?
> 
> http://www.electrokit.com/g1201-aluminiumlada-gjuten-tat-171x121x55mm.42596


Yep, I've been looking at similar boxes from Bud that can be bought from the usual electronics distributors. Something from this family of enclosures, more specifically, because they have an o-ring for sealing against water intrusion and mounting flanges. Can't underestimate the value of mounting flanges in this application!



steelneck said:


> Update. As for connections, just have wires going out of the box through proper seals. Locktite the screws if you do not want people to poke inside without breaking warranty (the foam rubber o-ring will melt if someone try to heat the locktite to be able to unscrew).


I'm still undecided on how to make the input and output connections. There is the method you mentioned, which is to put cable glands on the box to feed wires to terminal blocks mounted on the board inside - which requires the use of the proper diameter wires to maintain the seal integrity and, of course, you'll have to open the box to make the connections - or using bulkhead connectors for the 12V side and a terminal block not unlike what is used on the Soliton controllers for the HV input and control signals. I am leaning towards your solution, mainly because I don't want to put the HV input and control signals on the same terminal strip; that's just asking for trouble (and even though accidentally connecting the traction pack to the LV control terminals would definitely be the customer's fault, that usually doesn't make the customer any happier).


----------



## Tesseract (Sep 27, 2008)

TheSGC said:


> If I could have a DC/DC converter for my EV (13.6v 50a+), with a 60 Hz 110v 2kW+ output I'd pay $1k for that any day... Then I wouldn't need a generator, and it would act has "jump start" for charging another EV if they ran out of power.


Hmm... interesting suggestion and one I would find personally useful, myself. There needs to be a transformer in the DC-DC to provide isolation between the traction and 12V batteries, and in all of the topologies I've been considering that transformer will always have the same applied voltage across it, so I could easily add another secondary winding for ~170V to be chopped by an H-bridge into 120VAC (or 325V for 230VAC).


----------



## bfuqua (Sep 6, 2012)

I am with TheSGC. I would pony up a grand for a DC-DC if you could add in a 110 VAC. That would solve a lot of issues and give me max use of my batter pack. PLEASE! bf


----------



## steelneck (Apr 19, 2013)

Tesseract said:


> Can't underestimate the value of mounting flanges in this application!


Right, without mounting flanges people have to open the box to mount it. Your box suggestion look very much alike the one i linked to, exept the mounting flange. There is of course the option to use a box without mounting flange and just screw an L-bracket on each side as mounting flange, depending on price and labor time of course, or just drill and thread some holes on the sides with small screws in them - mount here.



Tesseract said:


> There is the method you mentioned, which is to put cable glands on the box to feed wires to terminal blocks mounted on the board inside


Not sure we understood each other here.. Look at the Elcon chargers, a cable going out on each side, AC in and DC out. That makes it simple and cheap to manufacture, no terminal blocks what so ever. A picture explains better. A lot of things use the same approach, some cables sticking out - connect this and that to this cable..


----------



## JRP3 (Mar 7, 2008)

> I would pony up a grand for a DC-DC if you could add in a 110 VAC.


I might go for it as well, but I think you'd vastly limit your market, unless it was an option.


----------



## EVfun (Mar 14, 2010)

JRP3 said:


> I might go for it as well, but I think you'd vastly limit your market, unless it was an option.


I don't know, that is an idea that gets my attention too. A wide input range DC to DC with 120 VAC out you could get yourself charged at a car show in a pinch. Just unplug the input from your pack and plug it into another pack. Then plug the AC output into your charger. It could contribute to running my home from my EV in the event of a power failure. I see something very useful.


----------



## TheSGC (Nov 15, 2007)

Tesseract said:


> Hmm... interesting suggestion and one I would find personally useful, myself. There needs to be a transformer in the DC-DC to provide isolation between the traction and 12V batteries, and in all of the topologies I've been considering that transformer will always have the same applied voltage across it, so I could easily add another secondary winding for ~170V to be chopped by an H-bridge into 120VAC (or 325V for 230VAC).


Using a transformer to provide isolation and two windings would definitely make it doable, with only a small amount of extra electronics. I'm not sure about your total design in your head, but a single DSP would easily handle the PWM for the DC/DC, along with the H-bridge for AC output. (Disclosure: I am a DSP Applications Engineer for a major DSP manufacturer. )


Besides using my EV as a battery backup for the house in the winter, I like going to car shows and I would love to have AC power to run a TV to show off the videos of my conversion, along with pictures. I also have a Solectria Force that I tend to kill the 22 year old NiMH batteries while range testing and require towing if I can't find a plug....


----------



## JRP3 (Mar 7, 2008)

TheSGC said:


> Besides using my EV as a battery backup for the house in the winter, I like going to car shows and I would love to have AC power to run a TV to show off the videos of my conversion, along with pictures.


You could do that now with a 12VDC to 120VAC inverter, unless you're running a large screen plasma or something.


----------



## EVfun (Mar 14, 2010)

JRP3 said:


> You could do that now with a 12VDC to 120VAC inverter, unless you're running a large screen plasma or something.


Not with the DC to DC converter I have. Well, I guess I could get about 2 amps at 120 volts (it's a good old Todd PC20-LV.) Having 2 kW of AC available would actually do something.


----------



## TheSGC (Nov 15, 2007)

JRP3 said:


> You could do that now with a 12VDC to 120VAC inverter, unless you're running a large screen plasma or something.


I've done that in the past, but I'd rather have an all-in-one solution, with a pure sine wave output and better than the 50% efficiency that the sub $300 inverters give.

Tess, let us know what you need for motivation/help/getting started on a DC/DC w/AC output. Several times last winter the power went out while I was visiting my girlfriends parents and they asked me why I couldn't plug my EV into the house, and I'd rather put some resources into a purposefully built EV DC/DC/AC system than hacking at a standard inverter.


----------



## Tesseract (Sep 27, 2008)

JRP3 said:


> I might go for it as well, but I think you'd vastly limit your market, unless it was an option.


Yes, the static AC inverter function will definitely be an option, and I won't be trying to design it into the first DC-DC converter, either, so as to not get bogged down by too many design details at once. However, just knowing that I want to add the ability to get 120VAC from the DC-DC converter at some point in the future will certainly influence some of the decision decisions today.


----------



## JRP3 (Mar 7, 2008)

I went for 2.5 weeks without power a few winters ago, using only a 1000 watt inverter to run my wood stove blower, a computer, flat screen TV, modem, and router, by hauling batteries to and from work. Would have been nice to just drive the EV to work instead, charge it up, and plug into it at night.


----------



## Tesseract (Sep 27, 2008)

TheSGC said:


> Using a transformer to provide isolation and two windings would definitely make it doable, with only a small amount of extra electronics. I'm not sure about your total design in your head, but a single DSP would easily handle the PWM for the DC/DC, along with the H-bridge for AC output. (Disclosure: I am a DSP Applications Engineer for a major DSP manufacturer. )





TheSGC said:


> I've done that in the past, but I'd rather have an all-in-one solution, with a pure sine wave output and better than the 50% efficiency that the sub $300 inverters give.


Well, there are lots of ways to skin this cat... The simplest is to wind a secondary on the DC-DC converter's isolation transformer to supply ~165VDC followed by an H-bridge with the switches operated with sine-modulated PWM (ie - carrier-based PWM) followed by an LC filter whose pole is set halfway between the desired 60Hz fundamental and the PWM carrier frequency. This reduces the size (and cost) of the LC filter components but still gives you a decent sine wave output from the inverter. For a fixed frequency single-phase inverter, a DSP is way overkill for the job, in other words 

However, controlling the DC-DC function *could* benefit from a DSP and would open up a lot more topologies for consideration. For example, if I could get two PWM channels that are 180 degrees out of phase and can span 0-90% duty cycle then I could instead use the "dual inductor converter" [DIC], which is a very interesting variation of the current-fed push-pull converter. A control IC for interleaved dual-channel boost power factor corrrection stages could probably be kludged into controlling a DIC, but it might be difficult or impossible to get good dynamic response from the control loop, then (most PFC ICs expect to achieve no better than a 6Hz control loop bandwidth).

At any rate, there is much to consider here and as for what I need to motivate me, well, the two things that are the most expensive to prototype in any switchmode converter are the magnetic components (more specifically, transformers) and, of course, the PC boards, because rarely does one get the design right the first time. Heck, I had to cut a trace and bodge in a jumper to correct a stupid mistake on a simple '3063 based buck converter. I've used this chip lots of times over the years for to make low power buck and boost converters and still managed to incorrectly wire up the Vcc, current sense and Vcollector pins in a board for the locomotive drive system...


----------



## Yukon_Shane (Jul 15, 2010)

allow me to muddy the waters even further and suggest you consider this inverter concept as part of a charger project rather then a DC/DC converter.

I know nothing about the design requirements but I'd say from a marketing perspective I'd happily pay several thousands of dollars for a good quality charger that could also serve as an inverter....my ceiling for a DC/DC converter (even with the AC ability) is probably around $5-600 

food for thought...


----------



## toddshotrods (Feb 10, 2009)

Tesseract said:


> ...and, of course, the PC boards, because rarely does one get the design right the first time...


You need one of these. Caveat: I know nothing about them, other than seeing this pop up in my news feed...


----------



## Tesseract (Sep 27, 2008)

Yukon_Shane said:


> ...I know nothing about the design requirements but I'd say from a marketing perspective I'd happily pay several thousands of dollars for a good quality charger that could also serve as an inverter....my ceiling for a DC/DC converter (even with the AC ability) is probably around $5-600...


No, a charger is not even remotely under consideration anymore because I have zero interest in competing against open source alternatives, and it will cost to much to develop *and* get safety certification (which the open source alternatives never bother with... fine, until one catches on fire and your homeowner's or car insurance refuse to cover the loss).

However, I can kind of see your point about the value of the inverter. Realistically, it needs to be able to deliver at least 2kW to be useful as backup power during an outage and that would require a far bigger transformer than is really necessary for a DC-DC converter. I mean, I know some OEM DC-DC's are that powerful, but very few - if any - DIYers really need 2kW of 12V power; heck, some still run their EVs on just the 12V battery, charging it up from the mains along with their traction battery.


----------



## Yukon_Shane (Jul 15, 2010)

Tesseract said:


> No, a charger is not even remotely under consideration anymore because I have zero interest in competing against open source alternatives, and it will cost to much to develop *and* get safety certification (which the open source alternatives never bother with... fine, until one catches on fire and your homeowner's or car insurance refuse to cover the loss).
> 
> However, I can kind of see your point about the value of the inverter. Realistically, it needs to be able to deliver at least 2kW to be useful as backup power during an outage and that would require a far bigger transformer than is really necessary for a DC-DC converter. I mean, I know some OEM DC-DC's are that powerful, but very few - if any - DIYers really need 2kW of 12V power; heck, some still run their EVs on just the 12V battery, charging it up from the mains along with their traction battery.


I'll save my comments on the open source charger for a different thread (in my desperation to find a good charger I'm one of the suckers that lost money on this) and agree with you on all points above.

Just one question though: if you integrate the inverter into the DC/DC now you're talking about plugging into the mains so don't you have the same safety certification requirement problem you'd have with a charger?


----------



## Tesseract (Sep 27, 2008)

Yukon_Shane said:


> ...
> Just one question though: if you integrate the inverter into the DC/DC now you're talking about plugging into the mains so don't you have the same safety certification requirement problem you'd have with a charger?


Not quite... or, I should say, not necessarily. The inverter would deliver AC power from a NEMA 5-15 or 5-20 receptacle - just like an automotive 12V to 120VAC inverter - and so would be subject to the same safety and EMC rules (which is to say, almost none, and almost all voluntary). So you plug your appliance or extension cord into it, rather than directly wire it your panel. Indeed, current "anti-islanding" regulations prohibit anything but grid-tie inverters from connecting directly to the AC mains.

Granted, anything which is intended to supply AC power should probably be safety certified to the same level as anything which consumes AC power, but, well... that's the wild, wild west that is the good ol' US of A for you.


----------



## TheSGC (Nov 15, 2007)

I'm going to go through my storage of power components in a few weeks when I get back from vacation, but I *may* have materials for winding high power transformers. 

As for PCBs, I agree those can get expensive, especially if populated. For small projects I've done, I've used ExpressPCB in the past, but I like to use real PCB tools, so I have had good luck with Advance Circuits (www.4pcb.com) on their PCBs and population service. 

My current DC/DC converter is a Zivan 14v/60a (840w), which I find sufficient for the 12v system, but doesn't allow me to hook up a 2 kW inverter to my 12v system. That, and the engineer in my twitches with all the losses from going to 144vdc->12vdc->120vac... It's also not sealed and if any decent water gets in the engine compartment, that's all she wrote. Oh, and it's my second DC/DC, my previous Curtis DC/DC didn't last very long.


----------



## ndplume (May 31, 2010)

Tesseract said:


> No, a charger is not even remotely under consideration anymore
> <snip>


Ok, skip the charger.


What about incorporating a DC-DC and/or 2KW Inverter into a Soliton Rev?


----------



## Tesseract (Sep 27, 2008)

ndplume said:


> Ok, skip the charger.
> 
> 
> What about incorporating a DC-DC and/or 2KW Inverter into a Soliton Rev?


That would require redesigning the controller(s) to incorporate the new functions and people who already have EVs - regardless of the controller used - won't be interested. I'd say that is more  than  .


----------



## ndplume (May 31, 2010)

Tesseract said:


> That would require redesigning the controller(s) to incorporate the new functions and people who already have EVs - regardless of the controller used - won't be interested. I'd say that is more  than  .


Well how do we get some  back into it? For YOU and your customers?

I've seen some folks asking/looking for an inverter that would take pack voltages in and output 220/120VAC without having to pass thru 12,24 nor 48VDC first. So maybe that is your main market and OBTW, you have a 100A, 14VDC on there as an option. And it can connect to the same cooling loop as your other products.

Someone will produce a portable inverter like this as opposed to the Vaporware I keep seeing on the net
http://www.plugincars.com/mitsubishi-unveils-blackout-inspired-i-miev-power-box-114873.html


----------



## Tesseract (Sep 27, 2008)

ndplume said:


> ...I've seen some folks asking/looking for an inverter that would take pack voltages in and output 220/120VAC without having to pass thru 12,24 nor 48VDC first.


Yep, an inverter that runs off the EV traction battery is something I would personally find useful and have given some thought to already. I was thinking of a non-isolated boost converter to create the constant 340VDC needed for a half-bridge inverter stage. For people with packs higher than ~330VDC the boost converter could be replaced with a buck. 



ndplume said:


> ...have a 100A, 14VDC on there as an option.


Not to echo Bill Gates here, but 50-60A at 14V ought to be enough for almost every EV. 



ndplume said:


> http://www.plugincars.com/mitsubishi-unveils-blackout-inspired-i-miev-power-box-114873.html


Interesting find... $1300 for 1500W seems a bit expensive (at current exchange of 117Y per USD). If there is no isolation between the battery pack and AC output (and none is needed, really) it should be possible to do at least twice that for the same cost. However, not with a ChaDeMo plug - that still seems to be ridiculously expensive over here.


----------

