[amsat-bb] Re: Lithium polymer batteries

[Gregg Wonderly]

The most predominate problem is people using the wrong chargers for them.  They 
think to themselves, "This is a rechargable battery, I can just use my expensive 
NiMh/NiCd charger I already bought".  The problem is, of course, that the LiPo 
cells have a completely different charging profile that is short-high and then 
long-low, instead of the previous long-high, short-low of the other common cell 
types.  Thus, people end up charging them for too long at High-C and boom, they 
overheat and catch fire.

The Radio Controlled Model industry has already gone through large failure 
occurrences with the charging problem, burning up multi-hundred dollar/hour 
investments, catching houses on fire etc.

Most people now charge LiPo batteries outside the models, and use a fired-clay 
pot or other heat tolerant container just to be safe.

Using the correct charger goes a long ways towards nearly eliminating all 
problems.  You have to have a temperature monitor to really do it right, but any 
production battery charging facility needs that.

Gregg Wonderly

whiteld at usa.net wrote:
> Following up on the Lithium polymer battery mention I Googled them and was
> disturbed to find:
> 
> -high fire risk. One seller offers flame retardant bags to put the cells in
> while charging them... for $25
> 
> -(as warned) high prices especially considering the more-unique balanced
> charger / discharger devices at ~$100 and up being required in addition to the
> cells themselves
> 
> -a hazardous materials uplift for FedEx shipment ranging from $25-$45
> depending on destination, on top of normal shipping rates
> 
> All of that tells me they're "not ready for prime time" though the current
> capacity vs weight looks very promising.
> 
> I will wait and watch, hoping the technology matures into something safer and
> less costly as time goes on. Likely it will, particularly the cheaper part,
> though it appears some safety issues have to be addressed meaningfully.
> 
> Thanks for the mention. It is interesting. 
> 
> Lowell
> K9LDW
> 
> 
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