From KR Group FYI, Virg

NetHeads,

Here's something I posted on my website last year after choosing my
battery.
Since I wrote this I have also found a tiny (3x2x5) UPS battery good for
7.2Ah, which will make a dandy isolated backup battery to keep the engine
running long enough to find an airport.  There may be better technology
than
what I have listed below, but this is where I'm headed at the moment, and
you can't beat the price.  It cranks my Corvair engine over...

I recently spent the entire DAY researching batteries. What got me
started
on this was seeing the Black Panther batteries in the Wicks catalog. They
list one that has 600 CCA (cold cranking amps) that I later discovered is
a
16Ah (at 10 hours) battery, for $113. I looked at Gills, Bells,
Interstates,
etc, and finally came full circle to the actual manufacturer of the Black
Panther, which is Hawker Energy Products (http://www.hepi.com/). The
standard aircraft batteries are typically 25 or 35 Ah. The AGM technology
used in the Hawker Genesis batteries makes them very reliable and with an
amazingly high CCA value for cranking things like large 6 cylinder
Corvair
engines. They are also permanently sealed (by definition) and can be
mounted
in any orientation.

My KR2S electrical system is going to be very current miserly. My radio
and
transponder are Terra (less than 2A combined), strobes are Kuntzlemann
(less
than 2A draw), ignition is coil and points (1A per 1000 rpm, according to
William) totaling 3A at cruise, and my nav lights are super bright LEDs
(Stefan Belatchev's idea) that draw less than .1A. All of this can be
turned
off so that only the engine's coil and fuel pump are running, which
totals
3.7 amps. My ignition switch will control ignition coil and fuel pump
without a breaker inline (if either quits, you're going down anyway), but
all other electrical items will be separate and will have
breaker/switches.
The G12V16EP battery that I chose will run this "minimum load" for 4
hours!
And if my Corvair runs anything like the rest of my cars, it'll start in
1
or 2 seconds, mininizing starting drain.

My EIS (Engine Information System) has programmable alarms, and the
voltage
trigger level can be set to something like 13 volts so that if my
alternator
quits charging, the EIS will immediately notify me and I'll have
something
like 2 hours to find a landing spot even without bothering to switch off
the
radio and transponder! For ME, that's a good enough margin. And it is
very
compact, with a height of only 3 inches, perfect for the upper firewall
shelf of a KR. Best of all, it weighs 13.5 pounds, half the weight of a
35Ah
Gill! The icing on the cake is that I ordered it for $64 from one of
Hawker's suppliers, Battery Specialties, Inc (1-800-854-5759). That's
half
what Wicks charges. Battery Specialties is the third place I called, and
they just happen to have a bunch of these on order, and they'll be
getting
them in 4 weeks. More typical is a 6 month waiting list! There must be a
reason why these things are in such high demand.

Yes, I'll do the testing to make sure that my electrical system has a
sufficient margin of safety (after all, my wife's going to be flying this
thing, along with my kids, someday), and if I need to, I can add another
13Ah battery (11 pounds) for a backup battery. These two batteries
COMBINED
weigh less than a Gill, and have almost the same reserve current
capacity,
but far more cranking power. If you're not inclined to live on the edge
like
me, you could always buy the G12V26EP for $98 and have one FINE 26Ah
battery, with 800 CCA and the potential to mount in any orientation. I
also
discovered the Interstate U1-33AGM, a 33Ah battery that you should be
able
to get at your local Interstate dealer for about $85. It uses the same
AGM
technology and is also permanently sealed like the others I've mentioned.

After talking to several other aircraft owners, I've found several others
using similar batteries, one even using an 8Ah battery to start and power
his 2.2 liter JPX engine, so I think I'm on the right track here...

Mark Langford, Huntsville, Alabama
mailto:langford@hiwaay.net
see KR2S N56ML at http://home.hiwaay.net/~langford

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