# Best Lithium battery option?



## EVfun (Mar 14, 2010)

My EV Buggy has a pack made of 39, 60 amp hour Thunder Sky LiFeYPO4 cells. It is a good pack, but not a very large pack, a little less than 7.5 kWh capacity. The practical available capacity is about 6.5 kWh (3.1 vpc at 54 amp hour) and it gives me about a 30 mile range.

The current pack is in a solid 16 gallon block. It is 14 inches by 33 inches by 8 inches tall, 3 rows of 13 cells. If a replacement pack was less than 14 inches deep it could be taller than 8 inches (11 inches deep would allow 9 inches in height.) Is there any higher capacity pack options that would fit in that space? I need to pull at least 35 kW peak for acceleration. The current pack is about 200 lb. and the buggy total weight with the pack about 1200 lb.


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## jonescg (Nov 3, 2010)

Most definitely.

What's your budget? Quite easy to get cells which pack almost twice the energy density of CALBs, but you pay for it.


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## Sunking (Aug 10, 2009)

The answer is *NO*.

You are asking for 5 times more Energy Density. LFP cells have an Energy Density of roughly 200 wh/L and you need 1000 wh/L. LFP does have the lowest Energy Density and Specific Energy Density of all the lithium batteries. However the highest of them all is Lithium Cobalt with a Energy Density of roughly 500 wh/L and you are asking for 1000 wh/L. With your limited volume at best are only going to get half the energy you needed. Of course the other problem when you use Lithium Cobalt you get two surprises that are really fun and exciting. 

1. You go from paying roughly 40-cents per watt hour for LFP to over $2 per wh for Cobalt.

2. This is the really fun and exciting part. You get to figure out how to integrate liquid cooling into your design with such a high energy density which eats into you limited battery space budget. Failure to do that and you get Chariots of Fire Buggy which is fun and exciting.

Unfortunately physics bites. Batteries are no match for liquid fossil fuel energy densities of 9 Kwh/L


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## pm_dawn (Sep 14, 2009)

I dont know what sunking drank this morning.....

But here is my take on it.

If you can raise the voltage of your system you could probably fit 50 of the CALB CAFI 72ah cells in the 33X11X9 space and get about 11.5kwh of max battery......

in about 100kg.

And it should be able to sport 35kw.

Just my take on it.
/Per


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## major (Apr 4, 2008)

Six EnerDel modules would just squeeze into a 14x8x33" box. Each is 7x8x11". That gives 9kWh at 90kg.


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## PhantomPholly (Aug 20, 2008)

If price is no object, range is already ok, and acceleration is objective then the Lithium Titanate cells might be the answer. They do seem to be offered in some places at high prices.


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## Sunking (Aug 10, 2009)

pm_dawn said:


> I dont know what sunking drank this morning.....


Apparently not my coffee. For whatever reason I thought he said 35 Kwh of capacity. My bad


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## Tomdb (Jan 28, 2013)

these might be a good fit.

http://store.evtv.me/proddetail.php?prod=CAM72FI

You could get roughly 66 cells in depending on your more accurate dimensions.

66x72x3.2 = 15.2 kwh


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## EVfun (Mar 14, 2010)

pm_dawn said:


> If you can raise the voltage of your system you could probably fit 50 of the CALB CAFI 72ah cells in the 33X11X9 space and get about 11.5kwh of max battery......


Those look very interesting. I could run 2 rows of 26, for a total of 52 cells. That would be right at the limit of my old DC>DC. They are half as thick as my older 60 amp hour cells. Aren't these the cells that some users have been having external current leakage issues with? Is the thin heat shrink added enough to really block that? Have their been any cell internal leakage issues from having a metal case?

52 * 72 * 3.2 = 11.98 kWh CALB CAM72FI
39 * 60 * 3.2 = 7.49 kWh Thunder Sky 60

That would be 160% of the capacity at a similar weight, upping the range from about 30 miles to about 48 miles. The cost would be about $6800 or so, depending on the supplier. I could likely sell the old pack, that still works perfectly, plus the spares I have, not used and holding charge, for about 60 cents (?) per amp hour ($2160 for 60, 60 amp hour cells.) It would also allow me about 51 kW of peak power at 5C, provided these CAM cells have no more sag than my older LiFeYPO4 Thunder Sky cells.


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## rtz (Jul 3, 2013)

Take a road trip down to California and bring a multimeter and run it directly on Keegans CAM cells and talk it over with him(that's what I would do if I was in the market and close): http://www.diyelectriccar.com/forums/showthread.php?t=69584


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## Hollie Maea (Dec 9, 2009)

EVfun said:


> Aren't these the cells that some users have been having external current leakage issues with? Is the thin heat shrink added enough to really block that?


If I wanted to use these cells, I would Kapton tape some 0.005" FR4 around each face. Doesn't really change the dimensions, but would eliminate frame leakage.


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## okashira (Mar 1, 2015)

Sunking said:


> The answer is *NO*.
> 
> You are asking for 5 times more Energy Density. LFP cells have an Energy Density of roughly 200 wh/L and you need 1000 wh/L. LFP does have the lowest Energy Density and Specific Energy Density of all the lithium batteries. However the highest of them all is Lithium Cobalt with a Energy Density of roughly 500 wh/L and you are asking for 1000 wh/L. With your limited volume at best are only going to get half the energy you needed. Of course the other problem when you use Lithium Cobalt you get two surprises that are really fun and exciting.
> 
> ...


Model S cells are about 680 Wh/L, and good power too.
I am selling them for less then 40-cents per watt hour. 
Liquid cooling not necessary. Tesla only uses it for environmental control, i.e., cooling the pack when stored at high SOC at high temperature in the sun, or heating the pack to improve performance/charging.
NCA is much more tolerant to degradation at high temp then LiFePO4.


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