Roy Page wrote:
When we bought our Piper Archer 2 years ago the previous owner cautioned
about leaving headphones plugged in in the rear seats.
He reckoned that with the headphones plugged in the battery would be slowly
drained.
I dismissed this caution as it did not seem to make any sense from an
electrical point of view.

When I came to start the engine yesterday, the cranking was very slow and
seemed like the battery was right down.
We have a new battery fitted a few months ago, so I doubt that as the
problem.
After flying for a couple of hours the engine cranking was back to its
normal speed.

I took a good look at the alternator and belt and nothing obvious was
noticed.
However, I noticed that a pair of unused headphones was plugged into a set
of the rear seat jack sockets.
They had been plugged in for about 2 weeks.

Now I wonder if they caused a slow drain on the battery while the bird sat
in the hanger for a couple of weeks ?

The aircraft has a SP400 intercom and an avionics master switch which is
always switched off when the engine is shut down.
The avionic line up is:-
KMA20, 2 x KX170's, KT76, KR86 and Flybuddy 820.

Maybe the old owner was correct ?
But what would cause the phones to take current off the battery ?

What does this knowledge base think ?

If there is a microphone (for intercom) the
headphones can use a little of current, provided
the intercom is on. IMHO, it is miswired if
it gets power when the battery relay (and switch)
is off.

In many airplanes, the clock gets power even with
the main switch off.

To verify, you need to switch the battery switch
off and measure the battery current with a suitable
ammeter - the built-in one is far too coarse for this.

HTH

--

Tauno Voipio
tauno voipio (at) iki fi