# Wiring my DC/DC converter?



## PeterH (Mar 20, 2009)

Surprised no one jumped in on this question... but I think I've solved it. I was reading more detailed documentation from similar converters and they clearly state to NOT connect the ground on the input side to anything. So that's what I'm going to do.

Hoping to conduct my first smoke test within a week or so.

Pete


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## Turbotom (Jul 13, 2008)

I am a little confused you say you are wiring a DC/DC converter but you also said you cut the 110 VAC plug off. Is this a 110 VAC to 13.8 VDC power supply or a DC/DC converter? Maybe list the make / model of what exactly you have.


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## PeterH (Mar 20, 2009)

I've been working with one of the guys in my local EV club that has built a number of conversions and who sells components and batteries. He sold me a power supply that runs on AC and provides DC. 

The web site for the company is: http://www.powermaxconverters.com

I'd provide a link direct to the specific device but their site seems to be dynamic and doesn't load different pages to display different information. 

I have their PM-55 model.

Everyone I've spoken with so far, assures me it will work well from the 144 VDC nominal, battery pack in my build. However, I've yet to conduct a smoke test with it. I'm only now at the point of wiring everything up and getting ready for the first application of power.

If you see a fatal error in this, please let me know... which of course, is why I've been posting questions.  Learned a lot so far, the easy way, and hoping to avoid learning more, the hard way! 

Thanks,
Pete


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## Turbotom (Jul 13, 2008)

I thought there would be a transformer in the power supply you describe. If there is a transformer it would not work. I guess if the guy that is selling it to you says it will work and he will stand behind it try it, if it goes Up In Smoke you'll know he was wrong. Good Luck.


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## jeffcoat (Apr 16, 2012)

Assuming that it is similar in its inner workings to the IOTA 45, it should work just fine.


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## PeterH (Mar 20, 2009)

jeffcoat said:


> Assuming that it is similar in its inner workings to the IOTA 45, it should work just fine.


 
Now that you've mentioned the IOTA, I recall my vendor saying it was 'just like an IOTA'....


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## PTCruisin (Nov 19, 2009)

PeterH said:


> Now that you've mentioned the IOTA, I recall my vendor saying it was 'just like an IOTA'....


Looking at their web site, it seems that they are identical to the IOTA converters, which are really 12v battery chargers.

You are correct in not connecting the green wire on the input side of the converter, but do connect the ground wire on the output side.

Instead of cutting off the ac plug, why don't you get just use a power cord to connect to the battery pack so you can unplug the dc converter and plug it in to an ac outlet when you are parking the car for long periods of time. This will keep the aux 12v battery charged from an ac source (if you plan on using an aux battery).

The reason you can use ac or dc on the input of the charger (converter) is because it uses switch-mode topology to down-convert the voltage. An ac input is rectified to dc and then chopped (switched on and off) at a higher frequency to increase conversion efficiency. So using a dc input gives you the same result.

Be mindful of the inrush current which can cause sparks and arcs when you connect the input side.

I would recommend a 10amp fuse on the input side.


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## PeterH (Mar 20, 2009)

PTCruisin said:


> You are correct in not connecting the green wire on the input side of the converter, but do connect the ground wire on the output side.


Really? I wasn't going to do so... but now that you mention it, I should. After all, the output side is islolated from the pack voltage.



PTCruisin said:


> Instead of cutting off the ac plug, why don't you get just use a power cord to connect to the battery pack so you can unplug the dc converter and plug it in to an ac outlet when you are parking the car for long periods of time. This will keep the aux 12v battery charged from an ac source (if you plan on using an aux battery).


REALLY wish I had thought of that two nights ago! 




PTCruisin said:


> Be mindful of the inrush current which can cause sparks and arcs when you connect the input side.
> 
> I would recommend a 10amp fuse on the input side.


At the moment I have one leg of the input side on a contactor to apply power only when the ignition is on. I've also fused both sides of the DC input on 10 amp 250V AGC fuses.

I am really taking my time on wiring everything up and asking questions whenever I'm not sure about something. Hoping to avoid stupid mistakes... so thanks for your input... think you helped me avoid one more possible mistake with the output ground. 

Pete


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## Yukon_Shane (Jul 15, 2010)

Hey Pete,

I'm fairly certain that this dc/dc is just like the IOTA that I have in my car in which case it should work just fine. The IOTA is designed as an AC to DC convert (charger) as well and it's been used in EV's as a DC/DC successfully for many years.

My understanding is that these types of AC/DC chargers have some sort of Power Factor Correction on the front end that allows them to accept AC or DC.

One thing that you'll see posted often on this forum is that these types of AC/DC chargers are not very robust as DC/DC converts in EV applications because they aren't designed to take the significant swings in power quality that occur within an EV application. There are a number of adaptations that I've seen recommended and you may wish to try. Here's a link to a decent discussion on this topic: http://www.diyelectriccar.com/forums/showthread.php?t=67346&highlight=iota 

I've followed Tesseracts suggestion and put a fairly large inductor inline with my DC/DC and it seems to be working but only time will tell. I'm hoping that some reputable company (starts with an *E* and ends with *tics*) will start to offer a DC/DC before mine inevitably dies on me.

shane


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## PeterH (Mar 20, 2009)

Yukon_Shane said:


> One thing that you'll see posted often on this forum is that these types of AC/DC chargers are not very robust as DC/DC converts in EV applications because they aren't designed to take the significant swings in power quality that occur within an EV application. There are a number of adaptations that I've seen recommended and you may wish to try. Here's a link to a decent discussion on this topic: http://www.diyelectriccar.com/forums/showthread.php?t=67346&highlight=iota
> 
> I've followed Tesseracts suggestion and put a fairly large inductor inline with my DC/DC and it seems to be working but only time will tell. I'm hoping that some reputable company (starts with an *E* and ends with *tics*) will start to offer a DC/DC before mine inevitably dies on me.
> 
> shane


Hi Shane, 

As I was reading your reply, I was thinking about something I read in the Soliton manual last night... about inductors. So great timing on your part! The manual is out in the garage at the moment but I think it mentioned placing an inductor on the output side of the charger and the input side of the DC/DC to help filter voltage spikes that could cause damage to the charger and DC/DC converter.

What inductor did you use? I was just about to do some searching to see what came up.

I'll be reading that other thread you pointed me to, next.

Thanks,
Peter


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## Tesseract (Sep 27, 2008)

Yukon_Shane said:


> ...
> I've followed Tesseracts suggestion and put a fairly large inductor inline with my DC/DC and it seems to be working but only time will tell. I'm hoping that some reputable company (starts with an *E* and ends with *tics*) will start to offer a DC/DC before mine inevitably dies on me.
> 
> shane




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.


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## PeterH (Mar 20, 2009)

Hey Tesseract, 

I'm a big fan of quality and willing to pay for it... so I'll be waiting to see what you come up with... cash in hand! 

I trust it won't need an external inductor of the sort suggested by the Soliton manual...  I need to find two inductors (for the charger and the DC/DC) but haven't a clue what to use or even how to select a suitable one.

Pete


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## Tesseract (Sep 27, 2008)

PeterH said:


> ..
> I trust it won't need an external inductor of the sort suggested by the Soliton manual...  I need to find two inductors (for the charger and the DC/DC) but haven't a clue what to use or even how to select a suitable one.
> ...


Rebirth Auto sells an inductor that I specified which should be big enough to handle even a large charger and DC/DC converter at the same time (remember, the output of the charger goes to the pack, and so does the input to the dc/dc converter).

You can also use a relay to disconnect the charger from the pack whenever the controller is powered on (and another relay to disconnect the controller from the 12V supply whenever the charger is plugged in - not a bad idea, both of those).

Otherwise, do an advanced search of posts by me with the word inductor in them as I have answered this question quite a few times here.


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## Yukon_Shane (Jul 15, 2010)

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.


Now we're talkin'!

I knew if we just bugged you enough you'd have to breakdown and build one of these.

Put me on the waiting list. $400 is a bit higher then I'd hoped for (isn't it always) but I think still reasonable for what you're offering. I could care less about the progrability (it's a dc/dc converter, what do you need to program anyway?) but if you could make it look pretty I'd appreciate it.

great news!

Pete: I don't remember exactly but I'm fairly certain it was a 100uH inductor I used. I took it right of one of Tesseracts posts on the topic 
where he offered a link to a digi-key inductor but unfortunately I can't remember which post it was.


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## palmer_md (Jul 22, 2011)

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.


Where is the signup list? Put me on the list for one.


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## PeterH (Mar 20, 2009)

I contacted Rebirth auto after not finding an inductor on their web site. They still sell them for $45 plus shipping.

From all the reading I just did as I reviewed all the discussions I found after an advanced search, I believe my elcon 5kw charger is probably already protected on the output side.

I also think if I don't protect my DC/DC, it will die sooner than expected from the ripple. However, I'm thinking I'll just accept that fact and save the cost of the inductor and put it in my new Evnetics DC/DC Converter fund. 

Peter


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## Tesseract (Sep 27, 2008)

No signup-list for the dc/dc converter, per se. When I finish designing it and it appears ready for prime time we'll make a bunch of them and query the dealer network for their interest.



PeterH said:


> I contacted Rebirth auto after not finding an inductor on their web site. They still sell them for $45 plus shipping.
> 
> From all the reading I just did as I reviewed all the discussions I found after an advanced search, I believe my elcon 5kw charger is probably already protected on the output side.


Yes, the Elcon chargers I have seen the inside of have all had an inductor in series with their output. The Zivans, however, do not. The big inductor that Rebirth Auto sells is good for chargers putting out 25A, so it's way overkill if all you need to protect is a 500W or so DC/DC converter (ie - 3-5A).



PeterH said:


> I also think if I don't protect my DC/DC, it will die sooner than expected from the ripple....


Hmmm.... "sooner than expected" in this case means "within a few minutes".... I took pity on you and searched DigiKey Yet Again: 100uH/7A/Toroid.


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## dladd (Jun 1, 2011)

Tesseract said:


> Hmmm.... "sooner than expected" in this case means "within a few minutes".... I took pity on you and searched DigiKey Yet Again: 100uH/7A/Toroid.


how is this functionally different than the CL-30 inrush limiter that I've seen suggested before for use on the input of the Iota's? They seem like very different components, do they do the same thing, or are they for different purposes? Do we need both, or just this inductor?


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## PeterH (Mar 20, 2009)

Hi Tesseract,



Tesseract said:


> Hmmm.... "sooner than expected" in this case means "within a few minutes".... I took pity on you and searched DigiKey Yet Again: 100uH/7A/Toroid.


Wow, I didn't realize it would die THAT soon. Thank you for your time looking that up. I'll order one right now and include it in the circuit before applying any power.

I suspected the Elcon had output protection from one of your posts I found... just had no idea the DC/DC would be so fragile...

Your proposed DC/DC will be welcome addition when it is ready for prime time!

Thanks,
Peter


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## Tesseract (Sep 27, 2008)

dladd said:


> how is this functionally different than the CL-30 inrush limiter that I've seen suggested before for use on the input of the Iota's? They seem like very different components, do they do the same thing, or are they for different purposes? Do we need both, or just this inductor?


An "inrush limiter" is basically a resistor that drops in value as temperature goes up. I don't like using them since they need to cool down to "reset", need to be sized for the max continuous load, and are happiest when the load is constant, not widely varying.

I instead suggest using an inductor because it will essentially appear invisible to DC but act like a resistor to AC (100uH is about 5 ohms at 8kHz; 9 ohms at 14kHz). This is generally enough to block most of the high frequency ripple from the controller yet incurs no additional loss doing so. Not a free lunch, but at ~$5 it ain't exactly going to break the bank, either.


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## somanywelps (Jan 25, 2012)

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.


$400? Yes please.


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