"Eric Greenwell" wrote in message
...
tango4 wrote:
Nickel Metal Hydride packs also dislike being too deeply discharged.
Apart from that they offer a lot of the benefits - High density, high
current, low temperature operation of other modern batteries. Compared to
lead acid 'gel cell' types they offer a reduction in mass of 50%.

My 9Ah 14.4volt NiMh battery is 2/3 the size of a standard 7 Ah 12v gell
cell and weighs 1/2 as much.

I'm looking for ways to fit more AH into standard glider battery boxes, so
people can add a transponder without decreasing the battery run time or
going to the trouble of installing another battery box. For example, going
from a 7 AH battery to a 10 AH pack might achieve this, particularly if
it's a 14 volt pack instead of a 12 volt pack.

What battery (brand and part numbers, if you can) and charger do you use,
and where can we get them?

--
Change "netto" to "net" to email me directly

Eric Greenwell
Washington State
USA

Hi Eric

I have the packs made up locally. They also supply me with a matched
microprocessor controlled charger. I am flying a Nimbus 3T with room for
both a 17ah Gell Cell ( right in the nose ) and a standard 7ah on the
cockpit floor behind the panel ( both standard schempp locations )

The replacement for the 17 ah is only 13 AH but is half the size and weight.
The replacement for the 7Ah is actually 9 AH but also only 1/2 the weight.
In practice the 9AH pack is delivering about 10 AH due to being better
suited to my current drain profile - about 750 mA continuous. ( Cost for the
9AH here in the UK was Batteries £79.50 each, Chargers £36.00 each They
are not cheap)

I had these packs made up as 12 cell packs. Nominally 14.4 volts but they
actually max out on full charge at about 16.5 volts - too much for Colibri
loggers and LX avionics. The voltage drops off to around 15 fairly quickly -
within 3/4 hour flying, and then tapers off to 14 volts for about 85% of the
profile. At 12 volts they are flat. In future I will have these made up as
11 Cell packs. This will keep the operating voltage to around 13 volts with
them going 'flat' at 10.5 and about 10 Ah. Still a lot better than the old
Gell Cell routine.

I have been using these batteries for a full season and their staying power
is impressive. I have an artificial horizon installed and even after a 5
hour flight there is plenty of go left to spin up the gyro without blacking
out radios, PDA or vario. Charging is simple , connect and go, 14 hour cycle
from flat to full. They could be recharged in as little as 2 hours but there
is little point in that and it does shorten expected lifecycles.

I expect at least 600 cycles out of the batteries and given that I only
charge the 9 Ah every 3 flights and the 17 hour once a month I reckon
they'll last as long as 10 or 15 years. By then we might all have little
fission devices or fuel cells installed anyway. That is of course if we have
any personal freedom left by then .......... sorry just a little cynical at
this time of the year.

I have a photo of the packs but your return eMail address bounces.

Ian