"Stephen Haley" wrote in message
...
I thought that some LIon are actually quite good at high current draw
applications. They are certainly making inroads into the model plane
market
now their price is dropping. The main problem with them is their
pontential
to explode if shorted out through thermal runaway and they require
specialised charging requirements. A secondary problem is that you cannot
measure the battery state through voltage.
The main advantages of lion are the light weight per amphour BUT they are
bulkier than lead acid by about a factor of 2.

I don't think you are right about the comparison with SLA's. Li-Ion has a
much greater power per unit volume and weight than Lead. The thermal
runaway has been solved with imbedded safety circuitry. (BTW, a shorted,
fully charged SLA isn't too nice to be around either but main fuses take
care of this.)

I don't need to monitor battery state if I know it will last twice as long
as I need it to. Cell phones with Li-ion batteries work just fine if
charged regularly. (A five-day battery charged daily is a no-problemo.)

BTW, I have no financial interest in Maxwell Technologies or Ultracaps, they
just have a nice web site that explains the technology well. Their point is
that batteries designed for low discharge rates will last a lot longer than
those designed for fast discharge. Ultracaps can supply short bursts of
high current for transmissions and recharge from the low discharge rate
Li-ion's. For a given size and weight, a Li-ion + Ultracap should be able
to power a lot more electronics than an equivalent SLA.

Bill Daniels