Lithium Iron Phosulfate cells?

pimpsmurf · Post by **pimpsmurf** » Thu Nov 17, 2005 2:48 pm

Don't know if I'm just way behind the curve, but these look like they might end up being usefull in some applications...

http://www.halfeight.com/forums/showthread.php?t=1229

-JNY

Cheesehead · Post by **Cheesehead** » Thu Nov 17, 2005 3:18 pm

LiFeP (Lithium iron phosphate) ) cells seem to have an energy density and discharge capability a good bit lower than that of LiPolys. The 4s1p pack shown on the website is rated at 1200 mAh @ 12.8 volts, with an 18 amp continuous discharge rate, with a weight of 168 grams. On the other hand, a Kokam 14.4v HD 1250 mAh lipoly pack would weigh roughly 140 grams, with an 18 amp discharge rate. However, the total power output ( in watts) is roughly 12% higher due to the higher voltage of LiPoly packs.
Also, the charger is much cheaper; 40$ vs. 230$.
On the other hand, they recharge quick, so you can buy two and have one on the charger while you're driving with the other. They're inexpensive, too; 45$ will get you the pack mentioned above, compared to roughly 70$ for the Kokam option. And not having to worry about them blowing up is nice too. The 4s1p pack should work nicely with a Mini LST or the like where weight is not much of an issue.

Where I'd expect these to find use first is in small portable electronics like cellphones, where people would likely pay good money to be able to charge their phone in twenty minutes, in addition to the reduced risk of having them blow up.

pimpsmurf · Post by **pimpsmurf** » Thu Nov 17, 2005 3:32 pm

Yes, but you can use a regular 4.1-4.2 lithium ion/lithium polymer charger on these cells because the cells don't heat up. You don't need to charge them past 3.35v/cell or so, but you can do it safely without heat buildup, which is what is so rad about them. When you discharge them, they don't burst. And you can charge them at 2-3C, which makes for a 35-45 minute charge time, which is freaking sweet. Sure, they are heavy as crap, and don't have the output to handle brushless mambas and such. I wish they made smaller length cells so I could put 2s2p in my MZM! =)

-JNY

Cheesehead · Post by **Cheesehead** » Thu Nov 17, 2005 5:02 pm

pimpsmurf wrote:Yes, but you can use a regular 4.1-4.2 lithium ion/lithium polymer charger on these cells because the cells don't heat up. You don't need to charge them past 3.35v/cell or so, but you can do it safely without heat buildup, which is what is so rad about them. When you discharge them, they don't burst. And you can charge them at 2-3C, which makes for a 35-45 minute charge time, which is freaking sweet. Sure, they are heavy as crap, and don't have the output to handle brushless mambas and such. I wish they made smaller length cells so I could put 2s2p in my MZM! =)

-JNY

I'd be surprised if they took 4.2 volts for long before losing capacity.

In response to your comments, the LiFeP cells can hande a mamba. Easily. Each can sustain an 18A continuous draw, which is more than sufficient for two mambas. Remember, the ever-popular 1200 mah NiMh cells used in most 1:18 size R/C cars cannot put out more than about 12 amps.
Also, a 3C charge would let you charge one in about 20 minutes, possibly less if you did not fully discharge it.

EDIT:
I read up a bit on the CC website, and admittedly, two mambas might be a slight problem. At 9.6 volts (3 cells), one could run two 5400's with no difficulty, but the 8000 would likely have some problems.