# Evnetics Developing a DC/DC Converter



## Yukon_Shane (Jul 15, 2010)

I thought this deserved it's on thread...



Tesseract said:


> I finally caved on this and am designing a DC/DC converter. To keep costs down it is not going to have any programmable frills - not even adjustable output voltage - but it will be water-resistant, if not water-proof, accommodate a very wide input voltage range (probably 90-425V), be naturally capable of paralleling, short-circuit protected, reverse-input voltage protected (no way to protect against connecting pack voltage to the 14V output, though) and somewhere around 40-50A max output current - depends more on the thermal stuff than anything else.
> 
> Should have a prototype done in a month or so. Estimated cost of the production unit will be pricey - probably in the $400 range because, sorry, we make kick-ass stuff in tiny quantities and don't use slave labor, so... definitely a "get what you pay for" kind of thing.


 
I don't know about the rest of you but I'm pretty excited to have a purposed built EV DC/DC convert that's available to the DIY community. My IOTA is probably the weakest component in my current conversion and I'll be happy to replace it with something that's design to handle up to 425 VDC.


Shane


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## Yukon_Shane (Jul 15, 2010)

Any updates on the progress of this project from the Evnetics guys?

I got $400 burning a hole in my pocket


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## Tesseract (Sep 27, 2008)

Yukon_Shane said:


> Any updates on the progress of this project from the Evnetics guys?
> 
> I got $400 burning a hole in my pocket


Not much since that post, I'm afraid. I've designed most of it in my head, along with a few calculations here and there to nail down some of the particulars, but it might be another month or so until I make a prototype.


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## etischer (Jun 16, 2008)

IOTA is the weak link in my conversion too, I've already had one fail. The voltage boost input (boosts output voltage from 13.8 to 14.3) has stopped working on my second one. The voltage boost is a great feature, saves the 12v battery from boiling when the ignition is off, and keeps the headlights bright when the ignition is on. 

It would be great to have a fanless DC-DC, is it possible? IOTA is not designed to take the heat of being trapped in a hot car in the summer, the fan is always going 100%.


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## ruckus (Apr 15, 2009)

etischer said:


> IOTA is the weak link in my conversion too, I've already had one fail.


Get a Chinnoz, Chennic, elcon, or whatever it is they call them this week. Use 4 headways as a 12v stabilizer. You will have no problems.

Of course, once it comes out, a 'made in U.S.A.' dc-dc would be a nice premium option. 

p.s. can you up the voltage to about 800?


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## TheSGC (Nov 15, 2007)

After a few dead DC/DCs I ended up getting a Zivan DC/DC for $550, so in the $400 range is a bargain in my books.


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## onegreenev (May 18, 2012)

Using a MegaPack for my DC DC. Works great. UP to 300 plus volts. Not usable below like 120 volts. Best if you are at least that or above. Fan runs all the time but I am setting up a thermal fan switch.


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## etischer (Jun 16, 2008)

ruckus said:


> Get a Chinnoz, Chennic, elcon, or whatever it is they call them this week. Use 4 headways as a 12v stabilizer. You will have no problems.
> 
> Of course, once it comes out, a 'made in U.S.A.' dc-dc would be a nice premium option.
> 
> p.s. can you up the voltage to about 800?



I'm running 340v currently, and need 60A output. It doesn't look like Chennic/elcon has anything, I'd have to run two in parallel.


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## skooler (Mar 26, 2011)

Jeffrey,

Put me down for one as soon as its ready!

Are you taking deposits!? (seriously!)

Cheers,

Mike


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## adeyo (Jun 6, 2012)

Sorry, newb question, but what exactly does a dc/dc converter do? ...& where does it fit in the EV system?


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## skooler (Mar 26, 2011)

adeyo said:


> Sorry, newb question, but what exactly does a dc/dc converter do? ...& where does it fit in the EV system?


The wiki on this site (top right of page has lots of information such as this.

http://www.diyelectriccar.com/forums/showthread.php?t=22818

Cheers,

Mike


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## Tesseract (Sep 27, 2008)

Nah, no deposits because then I'd have to answer annoying "when will it be ready" emails... 

60A at ~14V output is a bit more than I was planning on. I realize that some people really do need that much current - mainly because of electrohydraulic steering (e.g. - like used in the MR2) - but the majority of vehicles would do fine with a 40A dc/dc, and the vast majority - probably 80% - would do fine with 50A. In trying to balance all of the various requirements like cost, efficiency, using the case as a heatsink, input voltage range, etc., it looks like 14V/50A is a reasonable upper limit.

I was planning on making it possible to trim the output voltage over a narrow range using an external resistor which could be used to boost the voltage when the ignition is on much like the IOTA's.

There won't be a fan and the box I intend to use (Bud ANS-3809) is both waterproof and has EMI gasketing. It's not too pretty, but it gets the job done. There is a black powder-coated version for $10 more, IIRC.

I just need to make a bit more progress on the other two projects (one EV-related, one not) before resuming work on the dc/dc.


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## dougingraham (Jul 26, 2011)

adeyo said:


> Sorry, newb question, but what exactly does a dc/dc converter do? ...& where does it fit in the EV system?


It takes your high voltage traction pack and gives you 12 volts so you don't need a 12V battery to power the car systems.

In point of fact it is a good idea to have a 12V battery and use the DC-DC converter as a charger for the battery. Think of it as an alternator replacement. You want a battery because if you have a catastrophic failure in the DC-DC you still want to have your lights and other safety equipment work until you get off the road. Using two independent DC-DC converters is a good compromise for not having a 12V battery because it is unlikely both converters will die at the same time. But a main traction pack issue will still take out both converters. This is why many people still recommend a battery. I am using an 8AH LiFePo4 pack and a 40amp DC-DC converter in my conversion.


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## ruckus (Apr 15, 2009)

I would very much recommend a small 12v battery to stabilize surge loads on the dc-dc (like intermittent wipers or vacuum pumps). I use 4 Headways to stay on the lithium side of things. Many people who have tried to use only a dc-dc without a 12v batt have them blow over and over. 

It is not good practice. 

Jack Rickard also has a theory that when your traction pack sags under heavy acceleration it can pull juice backwards from the dc-dc caps and cause them to blow. He recommends using a 1-way isolator on the dc-dc input to prevent this. Not a bad idea.

With these 2 precautions, most dc-dc failures would likely be avoided.


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## adeyo (Jun 6, 2012)

Awesome. That link answered my question...thank you! I am already planning on running an alternator off the front shaft of my motor and using an auxiliary battery. I never knew this to be the purpose of a dc/dc converter. :thumbup:

Edit: thanks Dougingraham! That really further clarifies things. Helpful


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## PStechPaul (May 1, 2012)

If you can accept an input voltage range of 127 to 373 VDC, you can get 16 amp switching chargers for about $80 each:
http://www.mouser.com/ProductDetail/Mean-Well/PB-230-12/?qs=AmzscSOM9ZYKHcxj/5DIEw==

Mean-Well also makes a 1000W version for 12V, 24V, and 48V:
http://www.trcelectronics.com/Meanwell/battery-charger-pb1000.shtml

The 12V 60A version is $278:
http://www.trcelectronics.com/Meanwell/pb-1000-12.shtml

It might be worthwhile to have a look at one and see if it meets the need. For a special purpose OEM maybe they could build a version designed for higher input voltage, and specifically DC. I'm sure these are also for lead-acid batteries, but maybe they are still OK for running the accessories. You could keep the same battery as comes with the car for conversions.

I'm looking into a DC-DC converter design that boosts 12, 24, 36, or 48 VDC up to 160, 320, or 640 VDC. Having it work the other way is essentially the same, and could use the same transformer and control circuitry. The changes would be the higher voltage MOSFETs or IGBTs, and other components such as rectifiers and capacitors. 

I plan to make a 2kVA and 5kVA model, although I may start with a 1kVA prototype because I already have some of the components, such as the transformer core and bobbin. I also found some EE55 ferrite kits on eBay for $13, probably good for at least 1kVA and possibly 2kVA. And they have E80 cores, good for 3-7kVA, for $14/pair. The bobbins are cheap and the wire is probably no more than $20-$30 or so. Everything else should be under $50, except for any special packaging. 

Maybe I can collaborate with you on this design. I'm not looking to make a lot of money on this and I'm really not set up for manufacturing, so maybe we should talk about details via PM or email. My immediate needs are for small tractor conversions and step-up converters, and I'm not even sure I can or want to go into production, but I've gotten the interest of some people on the tractor forum so there may be a market.

Good luck!


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## dladd (Jun 1, 2011)

Tesseract said:


> I was planning on making it possible to trim the output voltage over a narrow range using an external resistor which could be used to boost the voltage when the ignition is on much like the IOTA's.
> 
> There won't be a fan and the box I intend to use (Bud ANS-3809) is both waterproof and has EMI gasketing. It's not too pretty, but it gets the job done. There is a black powder-coated version for $10 more, IIRC.
> .


not that you asked, but here's what I think.  I like the voltage boost idea, my DC/DC is always at 13.5v, and my headlights are noticeably dim compared to my other cars. Of course my car is almost 20 years old so it could just be old wiring and dim lights, but I think some of it is the lower voltage.

I love the no fan and waterproof idea, but I think it would be a mistake to not make it cool looking. Lets be honest, the awesome looks of your controllers is a definite selling point. Look at how much work folks go through to make sure their Solitons are front and center in the motor compartment cause they look so awesome.  I know you are not going after the bottom end market here, a few more bucks for a good looking custom box would move it appropriately upscale visually. Perhaps out of the question at DIY market quantities though?


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## PStechPaul (May 1, 2012)

These enclosures look nice. 6" x 6" x 2", green anodized extruded aluminum. On sale for $25:

http://www.newark.com/box-enclosures/b4-160gr/enclosure-instrument-aluminium/dp/26K9071

Or a larger one 8" x 6" x 2", blue, for $36:

http://www.newark.com/box-enclosures/b4-220bl/enclosure-instrument-aluminium/dp/26K9075

Or:

http://www.newark.com/hammond/1455zt1601/enclosure-wall-mount-aluminium/dp/50H5773

Or if plastic is OK, only $14:
http://www.newark.com/jsp/search/productdetail.jsp?SKU=10R1327
http://serpac.com/userprints/WM073i_UP.pdf


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## EVfun (Mar 14, 2010)

ruckus said:


> Jack Rickard also has a theory that when your traction pack sags under heavy acceleration it can pull juice backwards from the dc-dc caps and cause them to blow. He recommends using a 1-way isolator on the dc-dc input to prevent this. Not a bad idea.


This was just rehashed a few threads ago after Tesseract gave me a lesson a month before that. It isn't that the controller caps supply power because the input voltage sags, they would supply just a little in a smooth action as the sag happened. That won't blow any fuse and won't upset the DC>DC unless you go below its rated input voltage (some DC>DC converters will blow up just for that.)

The problem is that the controller is switching about 15,000 times each second. If the caps in the DC>DC try to follow that the input fuse will blow because it measures the current both ways and adds them up. If your DC>DC starts supplying and then receiving 30 amps back and forth constantly with the controller switching then the input fuse will likely blow. It should do that because heating caused by resistive losses goes both ways too. The diode will prevent the 30 amps from leaving the DC>DC but it is still using power off those caps (without the pack able to charge them for that tiny fraction of a second because the pack voltage is less than cap voltage) and when the controller power section switches off the current will rush into the caps. Depending on pack voltage swings, the impedance between the controller and DC>DC, and other factors (impedance and capacitance is everywhere) the blocking diode could solve the problem, or do almost nothing to help. 

An inductor in the power line to the DC>DC can help, consistently. They are cheap and Mouser of Digikey, less than $10 for the part. If you are using any controller that might reflect to much ripple onto the system bus by all means use this simple fix for the DC>DC and avoid a half fix with a diode.


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## Tesseract (Sep 27, 2008)

dladd said:


> ... I like the voltage boost idea, my DC/DC is always at 13.5v...


13.5V is too low to properly charge a 12V lead-acid battery but it shouldn't result in noticeably dimmer headlights. I would check the voltage at the headlights to make sure you aren't losing too much in the wiring (which, I should note, is often intentionally sized too small to reduce the inrush current stress).



dladd said:


> ...I think it would be a mistake to not make it cool looking....


We don't disagree in principle, but in practice this is a tougher argument to make because it is difficult to nail down the exact cost of a custom enclosure. For our controllers it's alright - not ideal, mind you, but alright - if we are off on our cost estimate by $100 or so, but that could be the difference between profit and loss for the dc/dc converter. Also, nickel plating is very expensive while anodizing is too inconsistent to use on aluminum castings. All in all my guesstimate is that a custom milled nickel-plated enclosure for the dc/dc would add $150 to the cost. That might make it too big a pill to swallow, particularly if it doesn't put out 60A or more.

Lately we've been kicking around the idea of combining the dc/dc and charger in one box... It seems like a good idea to me, and eliminates some of the cost concerns with a custom enclosure, etc., since the charger would require one anyway.


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## skooler (Mar 26, 2011)

Hi Jeffrey,

What kind of size charger are you thinking of (in kw)? Or will you have more than 1 option?

Will it be possible to parallel them?

Either way... Put me down for the one!

Cheers,

Mike


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## Tesseract (Sep 27, 2008)

skooler said:


> ..
> What kind of size charger are you thinking of (in kw)? Or will you have more than 1 option?
> 
> Will it be possible to parallel them?
> ...


I just started on the design so can't answer any questions yet. It will be isolated, it will be at least 8kW, and it will be programmable. That's about all I've nailed down right now.


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## Woodsmith (Jun 5, 2008)

Tesseract said:


> Lately we've been kicking around the idea of combining the dc/dc and charger in one box... It seems like a good idea to me, and eliminates some of the cost concerns with a custom enclosure, etc., since the charger would require one anyway.


I like this idea.

The more I read about your products the more I feel I should be saving for and planning around using them.

It may mean I can't afford a battery pack but I can cross the bridge then.


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## Yukon_Shane (Jul 15, 2010)

Tesseract said:


> Lately we've been kicking around the idea of combining the dc/dc and charger in one box... It seems like a good idea to me, and eliminates some of the cost concerns with a custom enclosure, etc., since the charger would require one anyway.


I think this is a great idea. The more integration the better; plus you're killing two problem areas with one stone.

Glad to see the evnetics charger is still on the table.


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## Emd (Jan 17, 2011)

Tesseract said:


> Lately we've been kicking around the idea of combining the dc/dc and charger in one box...


Not in favor because
-I already have a charger (although if I needed one, I'd probably buy one from Evnetics )
-I need more than 50A from the DC-DC... I don't think I'd buy two DC-DC + Charger combos to get there...
-If something fails (DC-DC or charger), I like to return only the affected item for service.

So please count my vote for keeping components separate.

Cheers!


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## PStechPaul (May 1, 2012)

Just to enhance my own understanding, I had thought that the DC/DC converter and charger, for 12V accessories, was a single unit, and would always be used with a regular lead-acid battery as may have been in the vehicle. And I had assumed that the charger would just keep that battery topped off from the main battery pack. Of course a separate AC-DC charger could be used to keep the accessory system charged up during extended storage.

Then there would need to be the main battery charger, which would need to be powered by AC mains of 120 or 240 VAC. And as long as that power was charging the main battery pack, the DC/DC charger would also be charging the accessory battery.

If the accessories battery was a LiPo type, then the charging profile would need to adjusted for that chemistry, but otherwise the design and construction would be about the same. And since well-designed battery chargers have an output current limit of perhaps 13.8 or 14.4V, they could also be used without a battery in case it fails and needs to be disconnected. In such cases it would be good to have a decent size capacitor in the charger to keep the voltage steady under momentary current surges, and to limit ripple and noise.

Is this correct, or am I missing something?


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## Tesseract (Sep 27, 2008)

PStechPaul said:


> If you can accept an input voltage range of 127 to 373 VDC, you can get 16 amp switching chargers for about $80 each:
> http://www.mouser.com/ProductDetail/Mean-Well/PB-230-12/?qs=AmzscSOM9ZYKHcxj/5DIEw==


Yes, most people are aware of the MeanWell switchers. We even use them as individual chargers for the 12V AGM batteries for our dyno. They do have a disturbing tendency to blow up every now and then, so not the greatest quality, but at $30 each (for the 150W version) it's a tolerable failure rate.

That said, we mounted them in a NEMA enclosure with multiple fans for cooling and inside said box they aren't subjected to vibration, impact, temperature extremes, or high humidity. They get none of these benefits when installed in a car.

It's admirable to try to find a less expensive product, but at some point you go too far down the price vs. quality vs. performance scale. The MeanWell switchers are well past that point in my professional opinion.



PStechPaul said:


> Maybe I can collaborate with you on this design. ...


Thanks for the offer, but the dc/dc converter won't be too much of a challenge for me. I've more or less designed it already, anyway, I just need to lay out the board, build a prototype, etc...


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## Tesseract (Sep 27, 2008)

Woodsmith said:


> I like this idea.
> 
> The more I read about your products the more I feel I should be saving for and planning around using them.


 Come to the dark side, Woody... We have cookies...


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## Tesseract (Sep 27, 2008)

Yukon_Shane said:


> I think this is a great idea. The more integration the better; plus you're killing two problem areas with one stone.


Ok, that's two votes for integrating the charger and dc/dc converter and...




Emd said:


> Not in favor because
> -I already have a charger (although if I needed one, I'd probably buy one from Evnetics )
> -I need more than 50A from the DC-DC... I don't think I'd buy two DC-DC + Charger combos to get there...
> -If something fails (DC-DC or charger), I like to return only the affected item for service.
> ...


...one vote against.

However, these reasons may not apply to the integrated charger + dc/dc.

1. Can't argue with that, though I have to point out that the same rationale could be used to argue against the development of any new product. 
2. If I integrate the dc/dc into the charger I won't have the same constraints w/r/t the maximum practical output current, so I'd probably aim for 70A instead.
3. The dc/dc would be an almost totally separate "module" inside the charger box. The only component it would share with the charger would be the ripple-blocking inductor. The main reason to put it in the same box is to save the cost of the enclosure (~$40-$50).

Otherwise, I happen to agree with on your 3rd point - I'm not a big fan of highly integrating multiple functions in one box (e.g. - charger and motor controller) precisely because it increases the likelihood of failure (mainly because there is an inevitable compromise in the shared components to allow them to do double duty).

Nothing's etched in stone at this point.


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## lowcrawler (Jun 27, 2011)

Throw a in a 120V AC plug for those of us that like to plug things in in the car or use the car as a mobile power source?


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## palmer_md (Jul 22, 2011)

Tesseract said:


> Ok, that's two votes for integrating the charger and dc/dc converter and...
> 
> ...one vote against.


I vote for the combined unit. I'd like a good charger and DC/DC and I'll be in the market for a pair early next year. Given your general description of the specs, it is just about what I'll be looking for, so I think your goals are very much on target. If they end up separate, that would be fine also, but mounting only one device seems simpler, and if reduced parts count (enclosure, inductor...) that is even better.


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## ricklearned (Mar 3, 2012)

Generally, I am a fan of modularity, but if there are manufacturing economics and value to the user, then I would go the other way.


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## jeremyjs (Sep 22, 2010)

I'd say integrate them and get both out the door, and if the demand is high enough in a year two go ahead and also make a separate unit for the DC-DC. New conversions need both. Existing conversions could probably use both, but don't want to buy a new charger. IMHO.


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## ruckus (Apr 15, 2009)

Tesseract said:


> Ok, that's two votes for integrating the charger and dc/dc converter...


Into the controller? That's PERFECT! 

14v, 110v, 220v, 440v. Everything I need in one big box. Perfect.

Where's the order form?

What is cost? Doesn't matter, I will pay it for such a product. No more dinking around buying, shipping, hooking up bazillion separate pieces. The 'power cube' does all that for you. simple. easy. robust. order today...



ps. don't say I never gave you good idea.


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## Overlander23 (Jun 15, 2009)

Tesseract said:


> Ok, that's two votes for integrating the charger and dc/dc converter and...
> 
> ...one vote against.


Count me in the against camp (or at least straddling the fence.) If it really does come down to the inductor and enclosure then why not have two products, the integrated and the separate DC-DC? Just charge more per unit for the DC-DC to make up for the inductor and case.

And I'd be interested in the DC-DC alone. I'd even be interested in a programmable charger, because I think you guys do the interfacing well. But if the only choice is an 8kw charger, how big and at what cost to get the comparatively small added bonus of a DC-DC converter?

In the end, I don't think people think any of the DC-DC converters that are currently out there are stellar. You don't hear as much of a complaint regarding chargers.


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## Dennis (Feb 25, 2008)

You plan to use bipolar transistors, mosfets, or IGBT's for the switching of the DC? Also are you going to use RC or RCD snubbers because I get tired of seeing such a cheap out way of taking care of back EMF from the transformer input side rather than use half bridge synchronous rectification to have a path for the back EMF. I say use half-bridge synchronous rectification. You are the quality over quantity type after all.

Finally, you do not plan to use a TL431 voltage reference as a bastardized OP amp in which they were really never meant to be used this way as so many manufacturers like to use them....


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## Tesseract (Sep 27, 2008)

lowcrawler said:


> Throw a in a 120V AC plug for those of us that like to plug things in in the car or use the car as a mobile power source?


Erf... you mean make the charger bidirectional, so it can invert the battery pack into 50/60Hz AC? That would be possible only if the charger had a single input and output voltage; once you make it so it can operate over the universal AC line range (100-265VAC) and deliver a variable output voltage/current the goal of bidirectional operation is a distant memory...


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## PStechPaul (May 1, 2012)

For AC power you can just get a 12V automotive inverter on the accessory battery. If you want serious power from the main battery pack you can use a VF drive. I got my 2 HP drive for about $60 and there are others on eBay for around $100-$150. It runs on 200-400 VDC and puts out 60 Hz three phase. You can set it for 120VAC output if that's what you need.


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## ruckus (Apr 15, 2009)

With a bunch of separate components you are depending on idiots like me to hook everything up and run the wires in a reasonable manner which probably quintuples the failure rate.


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## dladd (Jun 1, 2011)

I personally am not a fan of the 'all in one box' idea. I'd rather have separate components. It allows more modularity in design, and easier/cheaper repair down the road when a component fails. Just swap out whatever 'box' failed instead of having to open up and repair it, or worse yet having to pull the whole power cube out to send back to a mfr for repair.

Sorta like the combo TV/VCR's they used to make. Cool idea, but you end up throwing out a perfectly good TV when the VCR craps out.


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## ruckus (Apr 15, 2009)

I completely agree with you. There are definitely downsides to everything. Hopefully, the cover would come off and each separate component would be easily removable with quick-disconnect wiring.

I am thinking like a Desktop computer. Lots of bits packed in there, but still easy to take apart and service. Imagine if your computer was littered all over your desk. Hard drives, disk drives, power supply, motherboard, etc.. What a mess!  That is the current state of EV's. A bit of a rats nest.


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## rwaudio (May 22, 2008)

I like the potential cost savings of the combo, but I have to agree that individual products make better business sense. The target market of one of these items is very small to start with, force the customer to buy both with no flexibility mixing and matching and the customer base gets even smaller.

If there was minimal cost difference it would be worthwhile but it's unlikely that you can "throw in" a good dc/dc converter for just over the cost of the charger.
IE Charger is $2500 or Charger WITH 50A dc/dc is $2600 attractive option
Taking the Charger from $2500 to $3000 just to include the dc/dc might not be attractive to some.

As mentioned by ruckus, simplification in wiring is always a plus though, and the combo would likely be more compact that two separate devices.

****prices made up just to compare points, I have no idea what these will sell for!!


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## ruckus (Apr 15, 2009)

Yes, but imagine it is 1975 and everybody is building computers out of a bunch of different components cobbled together into a junk pile and then some guy figures you might as well stick the whole mess in one box and put an apple sticker on it...

If EV's are to appeal to the masses they must be simple.


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## toddshotrods (Feb 10, 2009)

ruckus said:


> Yes, but imagine it is 1975 and everybody is building computers out of a bunch of different components cobbled together into a junk pile and then some guy figures you might as well stick the whole mess in one box and put an apple sticker on it...
> 
> If EV's are to appeal to the masses they must be simple.


The problem with that logic is you're preaching it to the DIY community. That all-in-one box with the Apple sticker on it, in the EV world is called Leaf, Spark, MiEV(sp?), etc. All sorted out and ready to go, in one pretty package - for a price.

The DIY community is more analogous to the guy who refuses to give Apple, HP, etc, their money and still orders all those components individually, or in grouped sets, and rolls his/her own. To those individuals, freedom of choice is vital.

However, I don't think grouping two components like a good charger and dc-dc in one package would be seen as controlling or restrictive.


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## onegreenev (May 18, 2012)

ruckus said:


> Yes, but imagine it is 1975 and everybody is building computers out of a bunch of different components cobbled together into a junk pile and then some guy figures you might as well stick the whole mess in one box and put an apple sticker on it...
> 
> If EV's are to appeal to the masses they must be simple.


Todays cars appeal to the masses and they are very complex. We need to continue forward and not backward. Back in 75 it was fine to cobble those boxes but those boxes grew up. Now we have better. They still appeal to the masses. What appeals to the masses is convenience.


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## Tesseract (Sep 27, 2008)

Appeal to the masses?!? I estimate that around 1000 cars per year are converted into EVs... In the entire world. Appealing to the masses doesn't even factor into our design process. If it did, we wouldn't being making stuff for this market in the first place! 

I've previously mentioned that I am not a big fan of "all in one" boxes unless there is a very compelling benefit to doing so. In the case of the dc/dc and charger, the main benefit is that it could allow kicking up the output power of the dc/dc for "free" because the money that would be spent on the output filter inductor and enclosure could be redirected to the actual power conversion components.

Any other benefits - such as reducing the amount of wiring - are more subjective, since that may or may not be relevant to a particular installation. For example, the charger should be mounted as close to the battery pack as possible while the dc/dc should be mounted as close to the 12V battery as possible, and those two things may be on opposite ends of the car.

So I am wavering on this one...




PStechPaul said:


> ...If you want serious power from the main battery pack you can use a VF drive....


This suggestion is creative, but bordering on irresponsible. Not every AC electronic device will appreciate getting hammered with a PWM approximation of a sine wave without first being LC filtered and most VFDs do not like to see unbalanced currents on each of the three phase legs. All in all, a recipe for disaster.




Dennis said:


> You plan to use bipolar transistors, mosfets, or IGBT's for the switching of the DC? Also are you going to use RC or RCD snubbers because I get tired of seeing such a cheap out way of taking care of back EMF from the transformer input side rather than use half bridge synchronous rectification to have a path for the back EMF. I say use half-bridge synchronous rectification. You are the quality over quantity type after all.


I use whichever device is most appropriate for the job!?! That said, I haven't used a bipolar transistor in a switcher since the early 90s. 99% of the time I use MOSFETs, and only very recently have I considered IGBTs, as their higher current vs. die area is rarely worth the more complicated gate drive circuit required at power levels below, say, 1-2kW.

I don't get your distaste for passive snubbers. They are a reliable way of both absorbing the energy stored in the leakage and stray inductances in the circuit, as well as damping the Q of the inevitable resonances between switch output capacitance and said inductance. Most means of recycling this energy - by using a quasi-resonant switch, for example - result in a less rugged design as a result of a disturbingly high tendency to fail at light or no load.



Dennis said:


> Finally, you do not plan to use a TL431 voltage reference as a bastardized OP amp in which they were really never meant to be used this way as so many manufacturers like to use them....


It is true that using a TL431 to drive an optocoupler for the feedback loop in a switcher is a bit removed from it's intended purpose as a variable shunt regulator, but it is almost always the opto itself that limits dynamic range and transient response, not the TL431! Dr. Ridley wrote an excellent article on using the TL431 in a power supply some years ago which I highly recommend reading.


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## Dennis (Feb 25, 2008)

Tesseract said:


> I don't get your distaste for passive snubbers. They are a reliable way of both absorbing the energy stored in the leakage and stray inductances in the circuit, as well as damping the Q of the inevitable resonances between switch output capacitance and said inductance. Most means of recycling this energy - by using a quasi-resonant switch, for example - result in a less rugged design as a result of a disturbingly high tendency to fail at light or no load.


It's mostly from seeing designs in where snubbers are abused well beyond their intended usage. Like in switching power supplies you see snubbers be used to absorb the circulating current when the transistor is in the off state instead of the use of a bottom half transistor to give the current a path. The result is a large metal oxide resistor that gets very hot and melts solder joints which results in the snubber failing and thus the transistor to fail. I have seen traces from the snubber sections of power supplies that are black which is a sign of extreme heat. 

This is a more appropriate approach: http://www.diodes.com/zetex/?ztx=3.0/[email protected]~49!top~5!curr~13

While you may still need a snubber, it will be much smaller since it will not be used to absorb the circulating current.


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## PStechPaul (May 1, 2012)

Dennis said:


> It's mostly from seeing designs in where snubbers are abused well beyond their intended usage. Like in switching power supplies you see snubbers be used to absorb the circulating current when the transistor is in the off state instead of the use of a bottom half transistor to give the current a path. The result is a large metal oxide resistor that gets very hot and melts solder joints which results in the snubber failing and thus the transistor to fail. I have seen traces from the snubber sections of power supplies that are black which is a sign of extreme heat.
> 
> This is a more appropriate approach: http://www.diodes.com/zetex/?ztx=3.0/[email protected]~49!top~5!curr~13
> 
> While you may still need a snubber, it will be much smaller since it will not be used to absorb the circulating current.


The use of an MOV to absorb recurring transients is simply poor design or an attempt at planned obsolescence and failure. MOVs degrade with every surge and eventually become leaky and short out or burn up. A zener type TVS is better suited to the task.

And using a snubber in place of a fast diode to provide a path for recirculating current is just wrong.

The design in your link is probably unusable for any more than a couple of watts. The transformer is driven by capacitors. Can you imagine how big they would need to be for 1000 or 10,000 watts?


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## Dennis (Feb 25, 2008)

PStechPaul said:


> The use of an MOV to absorb recurring transients is simply poor design or an attempt at planned obsolescence and failure. MOVs degrade with every surge and eventually become leaky and short out or burn up. A zener type TVS is better suited to the task.
> 
> And using a snubber in place of a fast diode to provide a path for recirculating current is just wrong.
> 
> The design in your link is probably unusable for any more than a couple of watts. The transformer is driven by capacitors. Can you imagine how big they would need to be for 1000 or 10,000 watts?


I never said anything about MOVS being an alternative. In fact the use of such devices is a sign of poor design decision since MOVS will fail eventually vs a resistor-capacitor snubber. The resistor-capacitor snubber mostly fails from what I have seen with the resistor getting so hot that the solder joint fails from heating and cooling over many cycles which results in the transistor being destroyed from the voltage spikes since the snubber circuit becomes an open circuit. 

Unfortunately, you do not want to use a pure diode across the input of the transformer either because that will collapse the magnetic field very quickly when the transistor switch is off. This will result in poor efficiency. You can test this if you ever built a car ignition coil as a high voltage supply and used a diode to protect the switching device which results in reduce output where as with a snubber you get fat, white, sized arcs which is a sign of high current.

This is where the half bridge topolgy comes into play as you can see capacitors are used and there is no direct short of the transformer input to collapse the magnetic field too quickly and you do not need to use snubbers to absorb all the energy, but just to absorb any spikes that are inevitable . The capacitors will not be that large of values since DC-DC converters typically operate in the 100's of Kilohertz range and thus the capacitors will not need to hold a large charge vs lower frequencies. Finally, this topoloy is available up to 500 watts. 

I do not see a problem with having three, 500 watt DC-DC convertors of this topolgy put inside the same box. You get redundancy this way rather than have your entire 12 volt system tied to a single high wattage DC-DC convertor that if it fails means your entire car is not usable. I suppose you could use a 12 volt battery wired in parallel, but that adds weight.....


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## EVfun (Mar 14, 2010)

Tesseract said:


> I estimate that around 1000 cars per year are converted into EVs... In the entire world. Appealing to the masses doesn't even factor into our design process. If it did, we wouldn't being making stuff for this market in the first place!
> 
> I've previously mentioned that I am not a big fan of "all in one" boxes unless there is a very compelling benefit to doing so. In the case of the dc/dc and charger, the main benefit is that it could allow kicking up the output power of the dc/dc for "free" because the money that would be spent on the output filter inductor and enclosure could be redirected to the actual power conversion components.


Could I offer 1 more potential strike against "all in one" boxes? Of the EVs being built what percentage are "reconversions," such as lithium upgrades, new owner of an abandoned EV, or repackaging the EV parts in a more suitable chassis? These builders often retain most of the old parts, replacing just what is needed or adding upgrades to make things more current state of technology. I suspect they will be reluctant to buy a new DC>DC just because they need a new charger, or vise versa.


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## PStechPaul (May 1, 2012)

Rereading your post, I thought you meant metal oxide varistors, rather than resistors. And I'm just not familiar with the topology shown in the link. I found a similar half-bridge circuit in the following app note, but it does not have the third capacitor, which I think may be superfluous:
http://www.st.com/internet/com/TECH...AL_LITERATURE/APPLICATION_NOTE/CD00003910.pdf

For my own purposes, I am planning to use a push-pull topology, for a step-up DC-DC converter. And I do not need regulation, so the PWM can be nearly 50% which makes almost pure DC after the FWB. The DC-DC converter being discussed here is used to convert the battery pack voltage of 144-300V or so, to 12VDC for the accessory battery. This is a new concept for me, so I don't have a good grasp of what is really needed and why these converters are designed as they are.


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## mharvey (Oct 30, 2009)

Maybe late but a vote against the integrated model. Mostly as mentioned these components are typically on opposite ends of the vehicle. I like the flexibility to locate them where it make sense, and with the integrated component, one function will almost always be less than ideal. Add $50 for a pretty enclosure and we'll just suck it up. 

Have you given any thought to a water cooling option for the DC/DC? Since we go through the trouble to water cool the controller, why not an option to eliminate the fan entirely and cool with rad fans. Just a thought. Hell if we can string enough heat makers together in a cooling cycle, we can eliminate those dual element heater.


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## PStechPaul (May 1, 2012)

I was curious about the performance of the half-bridge PWM switchmode supply, so I modeled it for a 144VDC input and a 15V output into 0.25 ohms for about 950 watts. I used a switching frequency of 50 kHz and I was able to get about 87% efficiency as well as very few transients. Here is the simulation:









It really works a lot better than I expected  and I might use this topology instead of the push-pull I've been working on. I have not modeled it for a step-up converter but it should not be difficult. If you want the ASC file to play with it is at: http://www.enginuitysystems.com/pix/Half_Bridge_144V-12V.asc

The main problem with the half-bridge is driving the high side MOSFET, but there are drivers for that.

Also, I added the 10 mH choke in series to reduce the 300A charging inrush to about 50 amps. It will also help filter any transients from the battery pack and controller or charger. 

This is not quite a finished design, but all that is needed is an output current regulator and float voltage control. I think that will be better as a separate circuit, rather than trying to adjust the PWM of the DC-DC. It seems to work much better with a 50% PWM as shown. Actually I am using 47.5% because I have a 500 nS deadband to avoid nasty cross-conduction of the half-bridge. 

The efficiency can probably be tweaked above 90%. The simulation shows only about 5 watts in each of the MOSFETs.


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## Joey (Oct 12, 2007)

I'm going to buy which ever product you offer, but I have a slight preference for a combined unit. If I were looking to replace a DC-DC and already had a charger I liked, it would be an issue (and there is a huge gap in the market for a proper DC-DC converter).

For me, key charger features: legendary Evnetics quality and reliability, 100-250 VAC input range, isolated output, programable charge profile, charge termination timer, reduced current draw mode when charging from a shared (low current) power source, an output signal that can interface to the Soliton controller to prevent driving off when the charger is plugged in, BMS interface port (to terminate charge if the BMS senses a cell over voltage).

Other possible features - delayed startup to charge at night if you have time of use power rates (my dishwasher delays start time by 1 hour for every press of the delay button), collect stats such as number of charge cycles, average wh / charge, wh on last charge.


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## Tesseract (Sep 27, 2008)

mharvey said:


> ...Add $50 for a pretty enclosure and we'll just suck it up.


$50 is the cost of the plain-Jane die-cast enclosure I mentioned before; a custom casting that is then CNC machined and nickel plated is going to cost a lot more than $50... probably at least $150. That kind of cost can be absorbed in a more expensive product like a motor controller, or charger, but it's tough to squeeze it into an exceedingly unsexy product like a dc/dc converter. If I put the dc/dc into a nice enclosure but have to charge $650 for it instead of $500 then the vast majority of DIYers will pass it over after (rightfully) concluding that too much of the price is tied up in aesthetics, rather than performance. Still, knowing how Seb is we'll probably take a crack at a custom enclosure anyway... 



mharvey said:


> Have you given any thought to a water cooling option for the DC/DC?...


My goal is to not need supplemental cooling at all - relying strictly on natural convection - but I won't know for sure until I build a prototype.


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## Tesseract (Sep 27, 2008)

Joey said:


> ...For me, key charger features: legendary Evnetics quality and reliability, 100-250 VAC input range, isolated output,


Yes to all of the above (plus power factor correction).



Joey said:


> programable charge profile


We will almost certainly dispense with any complicated charge profiles and instead go with a simple CC bulk charging mode followed by a CV topping-off mode, with periodic checks of the open circuit voltage. If any additional "intelligence" is added to the charging algorithm it would be Coulomb counting to allow replacing a precise number of Ah.



Joey said:


> ...charge termination timer, reduced current draw mode when charging from a shared (low current) power source, an output signal that can interface to the Soliton controller to prevent driving off when the charger is plugged in, BMS interface port (to terminate charge if the BMS senses a cell over voltage).


Charge termination timer - definitely. With a non-volatile memory so a glitch on the power line won't reset it.

And power will definitely be reduced below 200V; user-programmable, of course.

To prevent the car from driving off when plugged in, however, I much prefer a microswitch that is opened whenever the charging cord is connected. That way, even if the circuit breaker trips you won't drive off with the cord still plugged in.

A BMS interface (both single digital pin and CAN bu) will likely be included, but all it will be able to do is terminate charging *early*. We will never hand over control of the charger to 3rd party hardware.



Joey said:


> Other possible features - delayed startup to charge at night if you have time of use power rates (my dishwasher delays start time by 1 hour for every press of the delay button), collect stats such as number of charge cycles, average wh / charge, wh on last charge.


These are all planned-on features, but they probably won't be in the very first code revision. Much like was done with the Soliton controllers, the first edition chargers will be rather basic but with a lower price tag to encourage early-adopters. As we add features, and as the more cautious types watch to see how well the chargers actually work, we will then raise the price to compensate for our additional effort and the "reduced risk" of buying a now-proven product.

Excellent comments, btw - thanks for that.


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## mharvey (Oct 30, 2009)

Tesseract said:


> $50 is the cost of the plain-Jane die-cast enclosure I mentioned before; a custom casting that is then CNC machined and nickel plated is going to cost a lot more than $50... probably at least $150. That kind of cost can be absorbed in a more expensive product like a motor controller, or charger, but it's tough to squeeze it into an exceedingly unsexy product like a dc/dc converter. If I put the dc/dc into a nice enclosure but have to charge $650 for it instead of $500 then the vast majority of DIYers will pass it over after (rightfully) concluding that too much of the price is tied up in aesthetics, rather than performance. Still, knowing how Seb is we'll probably take a crack at a custom enclosure anyway...


Understood. However like the controller, you get what you pay for. And for those of us having to support customers long after the conversion, the quality is paramount as DC/DCs are classic fail magnets. Industrial "unsexy" is just fine as long as it's durable and purpose-built for the environment it will be used. I think it's great that you guys are looking at doing this. Long overdue. 



> My goal is to not need supplemental cooling at all - relying strictly on natural convection - but I won't know for sure until I build a prototype.


Awesome. There was some discussion about fans earlier. Just thought I'd throw in the liquid cooling idea as I haven't seen it mentioned.


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## JRP3 (Mar 7, 2008)

Integrating the DC/DC with the charger is going to leave a lot of potential customers out in the cold. There are hundreds of Iotas and Meanwells on borrowed time that will need replacing, but most people with chargers aren't having the same number of problems. How many people are going to replace a functioning charger just to replace their DC/DC? Ideally you could offer both configurations, but if you have to choose just one it seems as if there is a much larger market for stand alone, since there is no combined alternative those interested in such would still probably buy your stand alone unit.


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## EVfun (Mar 14, 2010)

Tesseract said:


> $50 is the cost of the plain-Jane die-cast enclosure I mentioned before; a custom casting that is then CNC machined and nickel plated is going to cost a lot more than $50... probably at least $150. That kind of cost can be absorbed in a more expensive product like a motor controller, or charger, but it's tough to squeeze it into an exceedingly unsexy product like a dc/dc converter. If I put the dc/dc into a nice enclosure but have to charge $650 for it instead of $500 then the vast majority of DIYers will pass it over after (rightfully) concluding that too much of the price is tied up in aesthetics, rather than performance. Still, knowing how Seb is we'll probably take a crack at a custom enclosure anyway...


You might look at just a custom cover of an off the shelf die-cast box as a path between $50 and $150. Another thought is to look at stock extrusions for the most of the box. The old Todd DC>DC converters (AC>DC motor home converters, really) had an enclosure built up from extrusions and a couple bent pieces. Their design wasn't for pretty so much as cooling, but it illustrates the general idea. I've rebuilt a few and when I do I replace the rivets with screws.


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## PStechPaul (May 1, 2012)

There are companies that make stock extrusions which may also include mounting feet, and you only need to add end panels and internal PCBs. Most automotive inverters are built this way, and they are dirt cheap as well as attractive:

http://www.rose-bopla.com/prod_pgs/bab/Prod_02_Custom_Build_A_ Box.htm

http://shop.xtech-outside.com/extruded-enclosures/rs-6030

http://www.hammondmfg.com/sinkbox.htm
http://www.alliedelec.com/search/productdetail.aspx?SKU=E1096019

The solid cast metal box is rugged, but the machining for connections and such might be expensive. Flat end caps are easy to CNC.


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## NabilAhmad (Feb 26, 2011)

I see a custom run extrusion being more viable than an off the shelf generic case. There are many domestic aluminum extrusion companies too.


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## palmer_md (Jul 22, 2011)

Has this product development been shelved or is it ongoing? I'd love to hear about the skunkworks shop at evnetics.


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## Yukon_Shane (Jul 15, 2010)

Tesseract made a referenced in another thred that they have shelved this dc/dc and the evnetics charger design until the sales for their controller improve. Apparently the market hasn't been terribly strong as of late. 

It's a bit of a shame but I'm getting the impression that evnetics isn't as interested in the DIY market as they once were. I guess you can't really blame them if there isn't any money in it.


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## Siwastaja (Aug 1, 2012)

Yukon_Shane said:


> It's a bit of a shame but I'm getting the impression that evnetics isn't as interested in the DIY market as they once were. I guess you can't really blame them if there isn't any money in it.


People want new things and are getting more and more interested in AC, so an AC controller might have impact on both sales and DIY community, if done and marketed right. But it is not an easy step to take. But, I think the time is coming closer when you have to take it, or die slowly... Just my two cents. DC has lived unexpectedly long so far.


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## Tesseract (Sep 27, 2008)

Siwastaja said:


> People want new things and are getting more and more interested in AC, so an AC controller might have impact on both sales and DIY community, if done and marketed right. But it is not an easy step to take. But, I think the time is coming closer when you have to take it, or die slowly... Just my two cents. DC has lived unexpectedly long so far.


Uh-huh, yep. It certainly *seems* like everyone is jumping on the AC bandwagon here, but the Curtis 1231C *still* outsells every other controller, according to one of the major EV component dealers. And yes, they sell the Curtis 1238 AC system, too.

Not only that, but DIY EV components sales in general appear to be trending downward. The primary culprit is the availability of OEM electric vehicles. It doesn't take a Harvard MBA to figure out that if Nissan has sold some 50000 Leafs (and counting), then at least some of those customers won't be converting a car as a result. 

Hence my earlier comment back in January about our need to move into a different market entirely, rather than just a lateral move within this one...


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## Siwastaja (Aug 1, 2012)

I agree and think that a possible market would be on very low-cost AC systems, for those who cannot afford OEM car and plan on making a low-range EV to save on batteries, in which case the motor and controller cost are meaningful.

But low cost also means low profit, and it is very hard to do without sacrificing quality.


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## Qer (May 7, 2008)

Siwastaja said:


> I agree and think that a possible market would be on very low-cost AC systems


 I'd say that Curtis has managed to establish themselves in that market fair and square and that competing with them will be pretty much impossible if you're expecting to actually live on it too. Hobbyists might have a niche here doing something like an AC-version of P&S (isn't Paul working on something like that btw?), but I'd say that's about it. That leaves high performance AC but, well, nah. I doubt there's enough of a market to allow a business to thrive. Especially if you also consider the fact that doing an AC-inverter is a lot more complicated than doing a DC-controller.


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## rochesterricer (Jan 5, 2011)

Tesseract said:


> Hence my earlier comment back in January about our need to move into a different market entirely, rather than just a lateral move within this one...


Are you implying that you might leave the EV world entirely and move into something like industrial motor controllers?


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## JRP3 (Mar 7, 2008)

Siwastaja said:


> I agree and think that a possible market would be on very low-cost AC systems, for those who cannot afford OEM car and plan on making a low-range EV to save on batteries, in which case the motor and controller cost are meaningful.
> 
> But low cost also means low profit, and it is very hard to do without sacrificing quality.


Plus you are competing with a growing market of used OEM EV's. Why bother with a conversion when you can eventually get a whole factory built EV with a reduced capacity battery pack for probably less than all the individual components would cost? Also eventually used parts from wrecked EV's. DIY EV's started with used forklift parts and will migrate to used EV car parts. Eventually there will probably be a market for higher end higher power components to soup up your EV.


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## Qer (May 7, 2008)

rochesterricer said:


> Are you implying that you might leave the EV world entirely and move into something like industrial motor controllers?


 Na, as long as the Soliton sells and the parts for it is available it'd be stupid to kill it, I'm even working on a new software release for adding some new features. However, develop an entirely new product (or doing major modification to existing ones) kinda has to at least pay for itself since we're not a charity. 

A general decline in DIY-interest makes it harder to justify investing time and money in new products, after all we all have bills to pay etc. I wouldn't rule out the possibility for new stuff in the future entirely (but no promises...), but at least for now the primary focus is elsewhere.


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## palmer_md (Jul 22, 2011)

ok, since we've reached the end of this discussion, I have a question. What is up with the Swedish meatballs at IKEA?

http://www.nytimes.com/2013/02/26/w...ts-meatballs-horse-meat-is-detected.html?_r=0

I used to love those things before I went vegetarian. I do miss them once in a while, and when I saw this story I was a little surprised.


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## Siwastaja (Aug 1, 2012)

That horse meat scandal is going on all over Europe . Apparently, suspicious meat that may have contained horse meat, has come from some large distributor used by many many companies. As such, I don't think horse meat as a problem, but it is a clear sign of serious lack of control. If that much of the origin of food is not in control at all, how about hygiene etc.?

Anyways. You may see a decline in DIY EV market in the USA and maybe Australia and NZ, but that's because you had that thing going on in the 90's and even before. Many people who are in the mental state of DIYing an electric car, have already done it. However, we are late here. I think it's just _starting_ now outside the USA and I believe you will have a growing market mostly in Europe. Asian market will naturally supply their own products, so it doesn't count. I have seen that especially Eastern Europe has a growing EV conversion market. They are also producing a lot of parts.


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## Yukon_Shane (Jul 15, 2010)

Tesseract said:


> Uh-huh, yep. It certainly *seems* like everyone is jumping on the AC bandwagon here, but the Curtis 1231C *still* outsells every other controller, according to one of the major EV component dealers. And yes, they sell the Curtis 1238 AC system, too....


 
How is this possible? I've been participating in this "hobby" we call EV conversion for several years now and I don't know of anyone (real or virtual) who is building with the Curtis 1231C controller anymore. I've actually been kind of curious as to why (if) they even make this controller anymore. To hear that this is still the best selling controller out there is very surprising. Are they selling it to go-cart manufacturers or something?



Tesseract said:


> Not only that, but DIY EV components sales in general appear to be trending downward. The primary culprit is the availability of OEM electric vehicles. ...


This is suprising to me as well. The "maker" or "hacker" movements seems to be at an all time high with "hacker" shops croping up everywhere and Limor Fried the 2012 Entrepeneur of the year (according to Entrepeneur magazine). Surely some of this interest should be spilling over to the EV conversion market? 

Perhaps it's just a matter of time before all these "hackers" get tired of making circuits that can turn an LED on and off and want to build something a bit more usefull like an EV....


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## Ziggythewiz (May 16, 2010)

Yukon_Shane said:


> How is this possible? I've been participating in this "hobby" we call EV conversion for several years now and I don't know of anyone (real or virtual) who is building with the Curtis 1231C controller anymore. I've actually been kind of curious as to why (if) they even make this controller anymore. To hear that this is still the best selling controller out there is very surprising. Are they selling it to go-cart manufacturers or something?


Even a Curtis 1221C will move anything under 2,000 lbs quite well. The 1231C is ~30% better.

I would wager more converts are made of rage than creativity. There are a billion hackerprojects you can do that are very cool and not nearly as costly as building an EV. When gas prices spike the rage builds and those hackers look for solutions. The solution they find is a DIY EV.

It's been a while since we had a gas spike; the economy has a long way to go to recover from the last. Someday, likely in 5-10 years, the next spike will swell our ranks and perhaps convince OEMs to get serious.


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## Yukon_Shane (Jul 15, 2010)

Ziggythewiz said:


> Even a Curtis 1221C will move anything under 2,000 lbs quite well. The 1231C is ~30% better.
> 
> I would wager more converts are made of rage than creativity. There are a billion hackerprojects you can do that are very cool and not nearly as costly as building an EV. When gas prices spike the rage builds and those hackers look for solutions. The solution they find is a DIY EV.
> 
> It's been a while since we had a gas spike; the economy has a long way to go to recover from the last. Someday, likely in 5-10 years, the next spike will swell our ranks and perhaps convince OEMs to get serious.


I would definately agree with you that the 1231C is a respectable controller for small vehicles and for a long time it was one of the few good options that ev converters had; however, today at around $1,700 for a new 1231C why wouldn't a person just invest an extra $300 and get a soliton Jr.? The Jr. has a max voltage of 340 vs. the 1231C's 144Volts, and has a continious current rating of 500 which is likely 5 times the continous current rating of the 1231C. Plus the Jr.'s high level of programability and it's integrated contactor/precharge circuit put it head and shoulders above the 1231C in usability and ease of installation.

If you figure the average person is going to spend somewhere in the range of $10-20k on their conversion why would they look to saving $300 on their controller?

I don't doubt that the 1231C is still the best selling controller I just don't understand why it's true and it makes me wonder who they are selling to.

I would definately agree with you that the economy is likely impacting the EV conversion market. In my opinion EV conversion is really primarily a hobby that requires a significant amount of upfront capital with the potential for some longterm payback. It seems to me that this type of industry will always suffer when the middle clase suffers.


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## Ziggythewiz (May 16, 2010)

An established brand can afford steeper 'deals' than a high tech, low volume unit. They were under $1400 when I was looking, but you can get a prebuilt Open ReVolt for half that now.


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## onegreenev (May 18, 2012)

There still under $1400


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## brainzel (Jun 15, 2009)

This thread went off topic:

We build our car 2009 with a 1231C, because Soliton 1 was too expensive and Junior wasn't available.
If I would start a new build (and I will), I would take a Junior.
If I could change our controller, I would immediately.

We are now at the max. Voltage (144V) and that limits our range extension.
If we had a Soliton, we could increase our battery pack one cell after the other.
That isn't possible for us now, and I hate it :-/

The EMV/EMC is also an inspection issue to pass in germany.

Back to the DC/DC:
I would like to have an "Evnetics DC 1" with a wide input range and a 400-600W output and an adjustable Voltage 12-14.5V.
But I can understand the issue, that it probably wouldn't sell enough units to get enough sausage on bread of all Evnetic guys


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## Yukon_Shane (Jul 15, 2010)

onegreenev said:


> There still under $1400


You guys have much better sources for parts then I do. The listed price for the 1231C on Evolve, EVSource and EVPropulsion are all right around $1,700. KTA seems to show a list price of around $1,650 but is currently selling it at a discount at $1,500. I can't find anyone under that price but it wouldn't be the first time that someone on this thread has schooled me on where to get good deals.

Regardless of the price discrepency I think my point still stands (highlighted by the previos poster): noone serious about a full sized EV conversion would consider using the 1231C anymore; it's a dinosaur.


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## onegreenev (May 18, 2012)

How about a Synkromotive. 192 volts and 900 amps max. $1600. Site still says MSRP price but the price is $1600. Quite configurable and if you really want it can be set to be your charger too. From AC or even a stationary DC source.


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## dladd (Jun 1, 2011)

onegreenev said:


> How about a Synkromotive. 192 volts and 900 amps max. $1600. Site still says MSRP price but the price is $1600. Quite configurable *and if you really want it can be set to be your charger too*. From AC or even a stationary DC source.


and yet there is *still* no mention of that in the manual or... oh, never mind. 

It is too bad about Evnetics and the DCDC, but I totally get it. I don't think there is a sustainable market here. Too small, too specialized, too finicky, too price conscious.


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## Yukon_Shane (Jul 15, 2010)

onegreenev said:


> How about a Synkromotive. 192 volts and 900 amps max. $1600. Site still says MSRP price but the price is $1600. Quite configurable and if you really want it can be set to be your charger too. From AC or even a stationary DC source.


excellent point.


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## Karter2 (Nov 17, 2011)

dladd said:


> It is too bad about Evnetics and the DCDC, but I totally get it. I don't think there is a sustainable market here. Too small, too specialized, too finicky, too price conscious.


 Actually i dont understand the decision to drop it .?
All EV's ..DC and AC,..do, and will, need a DC/DC step down supply for the aux systems.
So, unless there is a good quality , good value, reliable , unit already available and hence not possible to compete against, this has to be a growing market .
..Or have i miss read something ?


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## JRP3 (Mar 7, 2008)

I'd guess there area already units available to OEM's at volume pricing, or they build them in house. They also typically use higher voltages than most of the DIY community, and probably a specific voltage, they don't need to build a unit that works for many voltages, which might keep costs down.


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## dtbaker (Jan 5, 2008)

Best price/performance dc-dc units I've had have been a Belktronix for a closed chassis design (675watt came in my Miata), or an ACME (600w for $200 from evolveelectrics.com) for open chassis w/ trimmable output.

tough to compete at that price.....

Chennics are cheaper ($99), but don't seem to last. I had two, and both died within 12 months use.


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## Yukon_Shane (Jul 15, 2010)

dtbaker said:


> Best price/performance dc-dc units I've had have been a Belktronix for a closed chassis design (675watt came in my Miata), or an ACME (600w for $200 from evolveelectrics.com) for open chassis w/ trimmable output.
> 
> tough to compete at that price.....
> 
> Chennics are cheaper ($99), but don't seem to last. I had two, and both died within 12 months use.


Belktronix looks like it might be a good option: it's closed chasis and appears to be built for the automotive enviroment; however, it's $300 and you have to pay extra for the soft start and the extra inductor to ensure that the ripple caused by high current controllers doesn't destroy it (kind of seems as though that should be built in).

The "ACME" dc/dc doesn't seem to me to be any better then the various other solutions that everyone in the EV conversion world have been using with mixed results for years (iota, chinnec, etc.). It's telling to me that suppliers only started using the "ACME" after the IOTA stopped being available....


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## Tesseract (Sep 27, 2008)

onegreenev said:


> How about a Synkromotive...


In the immortal words of Ronald Reagan, "there you go again..." 



dladd said:


> ...It is too bad about Evnetics and the DCDC, but I totally get it. I don't think there is a sustainable market here. Too small, too specialized, too finicky, too price conscious.


Yep, you've pretty much nailed it. The DIY EV market is _way smaller_ than people here tend to assume. Controller sales volumes are in the hundreds per year, not the thousands or even tens of thousands that would otherwise seem reasonable, given that there are something like ~250M cars on the road in the US alone.

So any product for this market will likely sell in similarly low volumes, which means it has to be profitable enough to justify the additional labor cost, especially if a new person has to be hired because the existing labor force is already maxed out.

With an estimated sales volume of 100-250 DC/DC converters per year at a profit of $50 each, at best, I can't come close to justifying it.

Which sort of explains why there isn't a good selection of DC/DC converters in the first place, eh?


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## Jan (Oct 5, 2009)

Tesseract said:


> Yep, you've pretty much nailed it. The DIY EV market is _way smaller_ than people here tend to assume.


I'm certain that's going to change at some point in time. Not because of the people who only want to drive cheaper. For them is a growing market of production EV's. But for the people who buy engines and other car parts already for years. People who want to pimp their ride. Tractor pulling. Drag racing. Mud or rock crawlers. And, what I personaly think will become a prety large market: Old timers. 

I'm very sure that's going to happen. At the moment you still get a lot of death threads and insults if you go the EV way in some of the above mentioned categories. But that's going to change. Like everything always changes.

And for some of those categories DC is still the best choice.


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## Tesseract (Sep 27, 2008)

Jan said:


> I'm certain that's going to change at some point in time.


I'm not certain of that. Our 2012 sales were almost exactly the same as 2011, and 2011 was only modestly higher than 2010. This is NOT a growth industry. Period. 



Jan said:


> And for some of those categories DC is still the best choice.


Again, I don't have any particular fondness for DC motors. My reluctance to develop an inverter for this market is for similar reasons as expressed above: the market is both too small and too price conscious. The fact of the matter is that an AC drive will cost more than twice as much as a DC drive of equivalent power, and when I have data staring me in the face that says people aren't even willing to spend $500 more for a Soliton Jr over a Curtis 1231C, well, can you blame me for being skeptical that a $6000 inverter will sell at all?

Would *you* mortgage your house to develop an AC drive for this market? Because that's the level of risk we are talking about here.


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