What are the highest discharge current cells available?

[Kartman]

Hi all,

Long time reader, first time poster.

I'm building a high powered go kart using the Colossus 12kw motor and a 700A kelly controller.

The hurdle I've come to is the battery pack. I dont have much room nor do I need much range, so I need to build a single 72v pack that can handle a very high peak of maybe 200 to 400amps for a few seconds and 100A continual. So far the Lifepo4 cells I've looked at are rated at 100A continual and 150A peak, I would have to have two packs in parallel.

Can anyone recommend a cell out there that may be able to do this? Has anyone experimented with quality cells discharging over their rated draw?

Regards, James

 

[wb9k]

If you want to go LiFePO4 (and I think there are good reasons for doing so), A123's cells are right up your alley. They are pricey, but you can get away with a much smaller pack than you could with other LiFePO4 and many other chemistries given your performance targets--big current taking precedent over big range. You can charge them at a relatively fast rate too. Two smallish packs with a big charger could give you lots of--maybe continuous--fun from the sound of it.

There are some Hymotion modules with A123 cells in them available from Sybesma's Electronics that may suit you very nicely. There's a listing in the used For Sale section of the forum:

http://endless-sphere.com/forums/viewtopic.php?f=9&t=58426&p=932343#p932343

(Scroll up to the top of the page to see the basic info.)
These might be a little big for you at the voltage you're after, but these (or one of the many BAE modules Sybesma's has) could be manipulated, or you may consider running at a lower voltage if your top speed requirements aren't too aggressive. Two of these modules wired in series took my motorocycle to 55-60 mph on rides over ten miles long when I had them mounted on the bike experimentally. Your requirements fit these modules like a glove from my perspective. This is a great way to get these cells at a great price--and fully tested too.

Hope that helps.

 

[Ohbse]

Lipo pouches would seem to be an ideal match for the application. Not as safe as LiFePO4, but a 12kw powered kart is about as far from safe as you can get anyway.

There are countless options, thankfully many of them will supply the current you're after without breaking a sweat.

http://www.hobbyking.com/hobbyking/store/__10308__Turnigy_5000mAh_6S_40C_Lipo_Pack.html

3 in parallel, 3 in series will give you a manageable sized pack that can dish out 500+ amps peak and easy continuous discharge of 300amps. 1KWh ish. As I assume this is a toy not a daily driver the cycle life will be more than adequate. If that's not enough power you can step up to 90C capable cells that could dish out power in the kiloamp range, however briefly before they were drained.

 

[wb9k]

Lipo pouches would seem to be an ideal match for the application. Not as safe as LiFePO4, but a 12kw powered kart is about as far from safe as you can get anyway.

Yes, so why make it that much worse? Why unecessarily risk turning an accident into a tragedy?

 

[Kartman]

Thanks for the replies.

Yes, Lipo pouches would be the obvious cheap and easy way to do it. Their safety and longevity scares me a bit though.

This kart may be a toy, but it's a high quality toy and I would like to get many reliable years use out of it. Actually thats the exact reason I turned away from petrol power, once set up this will just drive reliably charge after charge. Quiet too and low maintanance.

I currently have it setup as an experiment with a low powered outrunner. Only geared for 35kmh but gets there real quick, its great fun. Cant wait to strap the Colossus on

 

[friendly1uk]

Are you just playing on this or do you race it? If you race, there will only be one choice.

 

[Kartman]

Just playing. I have an excellent legal concrete area available to me.

Whats the one choice if it were raced? It couldnt be raced in Australia currently because there is no E category. Maybe one day in the future.

 

[mistercrash]

I would think that Used Nissan Leaf cells is a good option.

 

[friendly1uk]

Just playing. I have an excellent legal concrete area available to me.

Whats the one choice if it were raced? It couldnt be raced in Australia currently because there is no E category. Maybe one day in the future.

I would want to check, but I'm quite sure it's lipo pouches from the RC world. I have seen lighter, but the discharge rates didn't compare. Some of them pouches have 3 figure C numbers, so you only need carry enough to reach the flag. Not lots of cells because their C rating was too low.

 

[Hillhater]

Re: What are the highest discharge current cells available?

That would probably be the Saft VL5U...a 400C, 5Ahr cell.
But you really do not need those.
If you want to avoid Nanotech, RC LiPo , then your next best for power to weight would probably be a suitably sized pack (18S, 10P), made from 18650 high power cells like Samsung 25R