Battery Help Needed

[Gibles]

I'm new to the EV scene and I'm pretty electrically illiterate so I need your help. My project is an electric go-kart which is going to use a 36V brushless DC motor (rated power: 10kW, rated current: 250A, weight: 18lbs). After days of scouring the web I've found three battery options: Li-ion(a123), LiFePO4, and good old LA. I'd like to stay away from LA due to the weight factor even though they're cheapest. My LiFePO4 options are as follows:

Thunder Sky: 3.2V 12 in series, rated at 60Ah OR the 90Ah version

Lightning Bolt: 3.2V 12s, rated at 50Ah OR the 100Ah version

My understanding is that I would also need some sort of BMS. The other option was to make a a123 Li-ion pack(or have made). The configuration I was considering is below:

3.3V, 12s4P which would give me a capacity of 9.2Ah at 30C


The Li-ion is most attractive to me but would that configuration be capable of running a go-kart for a decent amount of time, or at all because of the low capacity? Does anyone else have a suggestion on battery type/config?

[kibble]

Welcome to the site!

Let me make sure we understand what you're saying.

When you say 12s4p are you talking about placing 12 batteries in series with 4 sets in parallel? :confused:

[Gibles]

Welcome to the site!

Let me make sure we understand what you're saying.

When you say 12s4p are you talking about placing 12 batteries in series with 4 sets in parallel? :confused:
yup! glad to be here.

[kibble]

Well, if you're using 12 batteries in series at 3.3V each, that would be 39.6V and then 4 sets in parallel should be about 4 times the capacity of a battery, which I'm not sure what it is for that particular battery.

9.2Ah total wouldn't last you very long though with a motor that draws 250A! Maybe a few minutes, at best.

What is the capacity of those batteries?

[2or3wheels]

more amps in a battery the longer they last

[Gibles]

Well, if you're using 12 batteries in series at 3.3V each, that would be 39.6V and then 4 sets in parallel should be about 4 times the capacity of a battery, which I'm not sure what it is for that particular battery.

9.2Ah total wouldn't last you very long though with a motor that draws 250A! Maybe a few minutes, at best.

What is the capacity of those batteries?

The total usable capacity of the a123 batteries is 2.3Ah, 4P makes 9.2Ah. They are rated at 30C which means they'd be rated at 280A of continuous discharge.
If the motor is drawing 250A it looks like I'd be getting 2.2 minutes without factoring in regen. I think I'd be better off with LiFePO4 now that I think about it. I just wish they weren't so expensive.

[DAElectric]

Hey I am thinking of using some Lithium too.
I would stay away from the Thundersky batteries though. There is no U.S. (sorry assuming that you are from the U.S.). I belong to an Electric Car mailing list anf there was a group by of the Thundersky. Half of the batteries were no good.

As for using A123 I dont think that this is a good idea for the lay person but if you realy want to try this link. http://ev.whitecape.org/insight/A123/
Guy does a complete walk through of the process.
Here is another link for people not familar with them.
http://www.killacycle.com 7.9@174 in the 1/4 mile.

I have never heard of lighting bolts so no comment there.

Whichever set of lithium that you go with you will HAVE to have battery management system in place. This will typicaly run $25 per battery.

I have not seen any BMS that is suitable for a large A123 set.

[DAElectric]

Sorry one last link
These are the ones that I am looking at.
http://www.beepscom.com/category_s/355.htm
40 amphour ones for the Kart and 200 amphour ones for the car.