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Technology Stocks : Energy Conversion Devices -- Ignore unavailable to you. Want to Upgrade?

To: Joe Master who wrote (3096)	1/28/1999 10:39:00 AM
From: Ray	Read Replies (2) \| Respond to of 8393

I can not give a definitive overview of re LiPoly/NiMH tradeoffs as I still lack some reliable numbers on performance, ruggedness, etc. Perhaps some others here can confirm or deny my speculations below. LiPoly now has up to about 170 WH/Kg capacity, which is a major advantage. Also, I have heard from several sources that LiPoly does not have a hazard problem like LiIon batteries. Further, LiPoly is believed to be relatively inexpensive, when production is "geared up". However, I am under the impression that LiPoly batteries are lacking in maximum power delivery - W/Kg, which is highly important for cordless tools/appliances and autos. Also, both autos and cordless tools/appliances demand rugged batteries that are reliable under abusive conditions. Further, this ruggedness MUST be proven for these applications; and it will likely be some time before LiPoly is so proven. I think one of the main reasons that most EV mfgrs and would-be mfgrs have settled on NiMH is that they have proven themselves - actually delivered on performance and durability, while other types have failed for one reason or another. IMO, for auto applications LiPoly probably requires substantially more development before being satisfactory, if ever. EV's have a special need for very high reliability (even one cell failing can be a problem, and EV's require many cells). GM's Delphi Division, who have been working jointly with Valence Technology, want to use LiPoly for auto Starting/Lights/Ignition. Perhaps for these uses, LiPoly might soon be a good battery. For starting, a "supercapacitor" could be used to provide the short-term/high-current needed, thus unloading the battery. (Supercapacitors are likely to be used widely in conjunction with batteries to provide "burst" or short term current capability. This can substantially extend battery life as well as improving the power performance of the combination.)