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.
At my level (Rank beginner using club equipment) the main problem is
normally that the battery is either getting old or is not charged. Going
back to my sailing days we converted to using NiFe batteries as we could
charge them at over 300 amps, 30mins motering gave us full batteries,, the
voltage was almost constant until completely discharged and they could be
badly abused (completely flattened) and still recover. I know that they
are/were used in aviation for engine starting but not sure if they were ever
used in flight.

For real usable results in battery technology I suspect we should look to
the new Hybrid Petrol/Electric cars being developed by Toyota but as with
all things it wil take time for them to be affordable/usable.

I suspect a real driver in Glider battieries will be the requirement in
Europe for Mode S transponders with some countries adopting them before
discrete iterrogation is switched on meaning that in some areas transponders
may be interrogated many times a min. This will require some real
improvement in battery technology for existing gliders where retrofitting
with solar charging would be difficult .

rgds
stephen

"Bill Daniels" wrote in message
news:fK5mc.27410$TD4.3881262@attbi_s01...
After reading the annual installment of the 12V vs.14V soap opera and the
"We can't power any more electronics" whine, I took a little time to read
the Maxwell Electronics information on their Ultracaps.

See: http://www.maxwell.com/index.html

Maxwell makes a pretty good case for combining a small ultracapcitor with
a
NiMH or Lithium-ion battery for use in typical consumer electronics like
computers and cellphones. It seems to me that the devices in our gliders
could use the Maxwell approach. Transmitters place a high demand on the
batteries for short periods and the varios and flight computers place a
low
demand for long hours.

The Sealed Lead Acid batteries most of us use are great for short, heavy
amperage demands but not so hot for powering electronics for long hours.
The typical NiMH or increasingly common lithium-Ion are great for low
current devices but not good at high current demands. Maxwell's solution
is
to combine a low amperage power source with an Ultracap so the Ultracap
handles the high-current short-duration, demands like transmitters and the
main lithium-ion battery handles the low-current, long-duration demand.

Of course, you still need the same AH's to go the distance but your
transmitter will get the voltage it needs at the end of a long day. We
need
our EE's to quit arguing about 14V vs. 12V and whip up a nice circuit for
an
Ultracap + Lithium-ion battery.

Bill Daniels