heat-tolerant rechargeable Li chemistry?

notrefined

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Sep 4, 2004
Messages
383
Location
Illinois
Is LiFePO4 better than other Li-ion chemistries for storage in hot environments, or are they all equally bad at this? Specifically, i would like to have a rechargable light that I can reliably store in my vehicle, which can get very hot when sitting in full sun in the summer. I am willing to take the energy density hit of LiFe cells, if they would stand up to this sort of abuse better. And of course, I need the same light and cells to work at -20 farenheit, as well. :rolleyes:

A123 brand LiFe cells seem to generally be among the best on the market; do they have any particular advantage with respect to extremes of temperature, aside from consistent high quality?
 

lordhep

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Dec 1, 2003
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Location
Sebring, FL
Is LiFePO4 better than other Li-ion chemistries for storage in hot environments, or are they all equally bad at this? Specifically, i would like to have a rechargable light that I can reliably store in my vehicle, which can get very hot when sitting in full sun in the summer. I am willing to take the energy density hit of LiFe cells, if they would stand up to this sort of abuse better. And of course, I need the same light and cells to work at -20 farenheit, as well. :rolleyes:

A123 brand LiFe cells seem to generally be among the best on the market; do they have any particular advantage with respect to extremes of temperature, aside from consistent high quality?

Just got some A123's to play with yesterday. So far I'm really impressed, took a 5amp charge an just got ruke warm. 6 2500mAh NiCd's ran our light for about 4 hours, almost got 5.5 hours out of two of the 2300 A123s. I'm playing with charging a 2 cell pack using a 7v dc adapter now. I don't think I'll have a balancing problem with a 700ma discharge.

Operating temp is -30c to +60c. Storage temp is -50c to +60c. There are some fakes clones out there so make sure you are getting the real deal. Here is a link to the data sheet http://rclipos.com/CoDocs/A123_26650.pdf

-Hep
 

Battery Guy

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Apr 28, 2010
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807
Location
Portland, Oregon
LiFePO4 are not better than other cells with respect to storage at high temperatures.

It is important to realize that it is the negative electrode that is most susceptible and first to degrade when a lithium-ion cell is exposed to elevated temperatures. All commercially available lithium-ion cells use the same material for the negative electrode: graphite. Also, they all use the same electrolyte: LiPF6 dissolved in a mixture of organic carbonates. When you heat a charged lithium-ion cell above about 60-70 degC, the lithiated graphite reacts chemically with the electrolyte, resulting in permanent capacity loss and impedance rise.

Since all lithium-ion cells use the same basic negative electrode and electrolyte materials, they are all approximately similar with respect to tolerance to high temperatures.

Cheers,
BG
 
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