Battery water consumption varies with use and seasonal ambient
temperature and humidity. I would speculate that the battery
specification, plate construction and water consumption differences
greater between manufacturers than between battery sizes. Mixing the
two just muddles the data.
Observation is but the beginning of evaluating available options so as
to reach a timely and appropriate decision. It is just as effective to
reduce electrical load as to increase capacity. There are many 13 amp
generators "out there" still giving reliable service so long as
limitations are known, weighed and and allowed for in both daytime and
night operation. Modern avionics require less electrical power than
older stuff. Old rotating beacons are real power hogs, as an example;
and should be replaced by strobe(s).
You are not depleting your battery's "reserve capacity" (from fully
charged) even when generator output falls to 100% of connected load.
Your wording suggests that your landing lights are only on when coming
in for a night landing. The few minutes in the pattern when your
actual electrical load might exceed 25 amps should not deplete a
healthy battery such that the GPS ceases to operate. Once one is in
the pattern and landing, you already know where you are. I would be
much more concerned if I lost my radio voice communication.
Landing lights are a luxury a pilot should be able to do without when
the airport has runway lights and they are are on. The "joke" about a
night off-airport landing is to turn on the landing lights just before
touchdown. If you don't like what you see, turn them off ;<)
On the other hand, If you like to go up shoot lots of night touch and
goes, or if you deem your landing/taxi lights "necessary" for extended
periods for additional insurance against a midair collision, the 35 amp
generator/regulator could better fit your "mission profile" than a
bigger battery for about the same weight penalty. It came with the 90
hp engine and the 25 amp battery in Forneys, Alons and M10s.
Regards,
William R. Bayne
.____|-(o)-|____.
(Copyright 2010)
--
On Jun 16, 2010, at 13:32, texasaviator wrote:
My personal experience with batteries, for what it is worth;
When I bought the coupe it had a 35 amp Concorde in it.
It lasted 9 years.
I now have a 25 amp GILL in it and have to keep adding water to three
of the cells about every three months.
I have upgraded the generator from the piddling 13 amp generator to a
25 amp generator and now have the required 15% ( or whatever) more
amps generated than consumed at peak consumption time, which is when I
am coming in for a night landing, have GPS, radio, landing lights,
strobes, MRX and transponder all working at the same time. the problem
is that I have the engine throttled back to 1000 rpm or maybe 1500 rpm
so the generator is not really putting out 120% of the consumed amps.
It sucks when your GPS goes off on the approach... So the 35 amp
battery seems to make more sense.
In the other coupe I have a 60 amp alternator that should put out
enough amps at 1000 rpm to keep everything running bright even with a
25 amp Concorde behind the seat.
AF.
N87333
N94694
