Backup alternator PA28-235...

I guess it's a pilot decision, which would make you feel safer, a second
battery or 7 more gallons of gas?
I'll go with the gas.

"Jim Macklin" wrote in message
news:gEqkg.38278$ZW3.10257@dukeread04...
A set of relays and diodes would allow the installation of a
second battery and a great deal of redundancy at fairly low
cost and weight. The standard alternator would charge both
batteries, only the second battery would be connected to the
essential bus of lights and avionics. A battery failure
kills the alternator on most aircraft and thus kills the
entire system. Having two isolated batteries give
redundancy as long as the bus is able to shed load.

Beech uses self-exciting alternators [and a generator will
produce power w/o a battery (but it isn't well filtered)].
On a Beech you can turn the battery OFF and still operate.
But in most Cessna and Piper aircraft the battery must be ON
for the alternator to function. A second battery and
modified bus can give redundancy. Load shedding can be
automatic or manual. You need to have diodes to control
current flow.


--
James H. Macklin
ATP,CFI,A&P

"soxinbox" wrote in message
...
| Point taken, but the original poster sounded like he owned
his own plane. He
| could probably spend the same amount of money on getting a
new alternator
| every year for ten years and still come out ahead. Or he
could get a new
| alternator and fix other problems that are more likely to
cause a problem. I
| will take a well maintained single of a bucket of bolts
twin any day.
|
| "Mortimer Schnerd, RN"
wrote in message
| ...
| Aluckyguess wrote:
| Why would you need an extra one. Wouldn't you just land
at the nearest
| airport if you where IMC.
|
|
| Aren't you the optomist.
|
| I've lost the alternator on a single engine solid IFR
flight over the
| mountains one night and it ain't much fun. I got down
OK before the
| battery went dead but it was definitely nerve wracking.
That's why I like
| twins. It's not the extra engine so much as the extra
alternator and
| vacuum pump. I've only had a very few engine failures
over the years but
| I've had several alternators and vacuum pumps go TU.
|
| When you fly crap as a freight dog you learn to
appreciate redundancy.
|
|
|
| --
| Mortimer Schnerd, RN
|
| VE
|
|
|
|
|
|
|
|