# PowerMax DC to DC Converter



## EVfun (Mar 14, 2010)

I suppose you hook it up and try it out. Some DC to DC converters will fail from operating on to low an input voltage. I would check the output voltage and if it is normal try adding a load like a headlight and check again. If it can hold the output voltage above 13.2 volts with decent load, and it doesn't get hot, it should be O.K.


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## dougingraham (Jul 26, 2011)

PeterH said:


> Hi there,
> 
> Just got a new Power Max DC to DC converter. This is supposed to take an input of 195 VDC to 280 VDC and convert it to 13.8 VDC.
> 
> ...


A lot of power supplies have a PFC (Power Factor Correction) front end. If they do this correctly it also makes the input to the device pretty universal. Generally they can operate from 57-400hz and 90-270VAC or 100-300VDC. The way it works is the front end boosts the input to near 400 volts DC and then bucks that DC voltage down to what you need. So most likely you can hook the hot and neutral either way to the traction pack and you will get 12VDC on the output.

It will probably work unless they have shipped you the wrong thing. Is the device placarded as to input and output voltages and currents?


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## Tesseract (Sep 27, 2008)

PeterH said:


> ...Just got a new Power Max DC to DC converter. This is supposed to take an_ input of 195 VDC to 280 VDC _and convert it to 13.8 VDC...
> The converter is configured with _a 110 VAC grounded plug as the input_.


The two phrases I italicized are mutually exclusive... If the converter is has a standard 120VAC plug then it *should* run on 135VDC to 185VDC, corresponding to a line voltage range of 95VAC to 130VAC.

144VDC is too close to the minimum voltage, especially since the pack voltage will sag when heavily loaded.

Power supplies with a PFC front end make much better candidates for this application, but even then 144VDC will be the low end of what is allowed.

Still, you likely didn't spend much on this thing so can't hurt to try it out. The worst that will happen is it goes up in a ball of flame...


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## PeterH (Mar 20, 2009)

Thanks for all the replies. Here are some pics to provide some details.




























So if I am willing to run a smoke test on this, just how do I connect it? I'm guessing on the output side it the Positive output would go to the main fuse block where the old battery positive went. The Negative output would go to chassis ground and the ground lug on the converter would also go to chassis ground.

On the input side what do I do with that 110 plug? Just cut it off and connect the ground and one of the hot lines to the pack voltage?

I'm months away from having the pack, so don't worry that I'll burn anything up in the next few hours experimenting. My batteries are on order but won't be here till mid December. But if you guys are willing to work with me on this, I'll eventually summarize all of this, with photos so that anyone following can see exactly what I did to use this in my build.

Just how much would you expect this pack to sag under load? I'm going to use 45 lithium cells for the main pack.

Thanks,
Pete


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## Yukon_Shane (Jul 15, 2010)

Alot of the DC/DC's used in EV applications seem to actually designed as small 12 volt AC/DC battery chargers like this. Once you get your pack just cut the end off of the plug to tie the nuetral and hot cable into the pack.

You may want to hold off on doing this until your close to complete the conversion. I find having the AC plug usefull in charging my 12 volts system while I'm testing various components to see the car is working correctly, etc. or to charge my Aux battery. With the dc/dc plug in (which I guess makes it an ac/dc) I know the aux. electrical side is receiving the voltage it needs. It's just one less variable to worry about when your trouble shooting.


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## PeterH (Mar 20, 2009)

Hi Shane,

Good idea, I won't cut anything until I really have to.

Meanwhile, I think you are using a lead acid battery in your design aren't you? Just for 12VDC of course.

If so, how are you regulating the charge of that battery from the DC converter?

If not, well, I've been reading too many threads lately...

Saw my first live Tesla Roadster at the local EV club meeting last night... way cool! But I'll bet it isn't something to take out into the snow. 

Thanks,
Pete


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## Yukon_Shane (Jul 15, 2010)

My Iota DC/DC charges to reasonable 13.8 volts which my Aux. Lead Acid is fine with so I can leave it on indefinately if I wanted to.

The Iota also has a "quick charge" option which pumps the voltage up to around 14.3 volts (I might not have that exactly right) which is a nice option for quicker battery charging but probably not a good idea to leave on for too long. 

I don't know about the snow but there was a Tesla at last years Vancouver Electric Vehicle Association event that was running some pretty fast laps in some of the nastiest rain I've ever seen. All you could hear was the water flying up from its back end as it flew by. Not as much fun as building your own though


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## PeterH (Mar 20, 2009)

I agree, if building my own weren't fun, I wouldn't be here! 

Did your Iota converter come with any documentation? Someone told me last night that this looked like the Iota, in fact, they referred to it as an Iota ripoff by another chinese company. 

The lack of any documentation bothers me... can you tell?


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## Yukon_Shane (Jul 15, 2010)

My Iota came with very little documentation and what was there wasn't very helpful for ev applications. This forum seems to be the best resource for how these products work (the folks here often seem to understand these products better then the manufacturer).

The pictures of your dc/dc do look alot like the Iota except it doesn't seem to have the "phone jack" plug that's used for the quickcharge option.

it's likely a very simliar model.


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## Power1111 (Nov 4, 2011)

The Powermax converter and iota are two totally different companies. They both work fine for this 144vdc to 12vdc conversion. The Powermax has a pot you can adjust for any out put voltage you want while the iota has a jumper for just two voltages. They both have a bridge rectifier. Trust me they work for this application. Just cut the plug. I know Powermax will help with questions and I'm sure iota will to. I use the Powermax and have no trouble. Just an FYI the IOTA is made in china as well. Read the box it says made in china


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## Coulomb (Apr 22, 2009)

PeterH said:


> On the input side what do I do with that 110 plug? Just cut it off and connect the ground and one of the hot lines to the pack voltage?


Don't connect your pack to the ground wire!

Just use the two line (hot) wires to connect to either end of your pack. Either ignore the ground wire, or connect it to the vehicle's chassis. I assume that the case of the DC-DC (really a power supply here) will get connected to chassis anyway when it is mounted.


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## Sparrow159 (Mar 30, 2010)

I just installed my PowerMax today. Don't expect the fan to come on or a light to come on as well. It works, but there's nothing to indicate it's on, unless you use a voltmeter. I hooked mine up to my 12V 60AH battery so the two will complement each other. I did test the DC to DC without the 12V battery and it works fine.

I do have a question. Since I'm running a 144V 100 AH lithium pack and I top balance often, will I need to disconnect the PowerMax DC to DC to do this? 

I would think any load on the pack would mess up a balancing effort.


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## GizmoEV (Nov 28, 2009)

Measure the load on the pack with the DC-DC as the only item connected. You will likely find it is very low unless you have a bunch of accessories on. While it will have a small effect on the balancing phase it will be minimal. Besides, unless you have an unbalanced load on your pack and/or you have some poor cells you won't need to balance very often. I haven't needed to balance my pack for more than a year. At the rate it is going it is still a long way off.


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