Alternator wiring

On Tue, 19 Feb 2008 12:50:02 -0800 (PST),
wrote:

Nope. Now it would read "charge" all the time, even during discharge.

The ammeter is an indication of what the battery is doing.
It needs to be wired as shown so that there are two directions of
electron flow so you know whether the alternator is managing to keep
up or not. If the alternator's output isn't wired to the bus itself
rather than the contactor, you'll have no idea if it's working
properly. The ammeter won't be able to tell you anything worthwhile.

Dan
'
Ah, that explains some other issue I have. In my flying homebuilt,
(the one I had to buy that was finished and flying because I didn't
know it would take so many years to complete my Glasair) It's amp
meter only shows a charge, but will never indicate a discharge. It
just goes to the center position when there's a load and the
alternator isn't turning. So where I the best place to install a
shunt? I need to rewire that darn thing.
Rich

On Feb 19, 7:27 pm, Pelican wrote:
Ah, that explains some other issue I have. In my flying homebuilt,
(the one I had to buy that was finished and flying because I didn't
know it would take so many years to complete my Glasair) It's amp
meter only shows a charge, but will never indicate a discharge. It
just goes to the center position when there's a load and the
alternator isn't turning. So where I the best place to install a
shunt? I need to rewire that darn thing.
Rich

Sounds like the ammeter is installed in the alternator's
output line. Doesn't belong there. A shunt won't fix that. The ammeter
should be connected like the diagram in that website I pointed out
ealrier: between the master contactor and the bus. Do that and all
will be fine. Piper used a loadmeter for some years, which was an
ammeter that had its zero position on the left instead of center, and
was used to indicate the alternator's output. Maybe that's what the
builder of your airplane was thinking of when he connected it between
the alternator and bus.

Dan

(snip)
If you put the ammeter between the battery's ground post and
ground, you'd have all the starter current running through it. It
would smoke pretty good. Starters draw hundreds of amps. Grounding the
starter separately would be pretty difficult, since it's grounded to
the engine through its mount, and the engine is grounded to the
airplane as a return path for both the starter and alternator, which
is also firmly grounded to the engine through its mount. The
alternator, though, should have a separate ground wire to keep noise
to a minimum.

Dan

Actually you can wire the ammeter using the ground post if you use an
adequate shunt to handle the load, I ran mine this way as per
Aeroelectric Bob and have not had any issues,