Battery or Alternator ...?

[Mooney13]

I was flying today and noticed my JPI flashing a warning "Battery 11.7".......then looked at my Ammeter reading "- 30"....and eventually the stock low/high volts in the panel flashed..

I flew for about 25 more minutes back to my home airport. My gear did seem a little sluggish coming down, but did come down.

I am wondering if this might be likely the battery or alternator or both.......or if there is something I can to to eliminate one or the other?

Thank you in advance for any advice!

 

[danb35]

Alternator isn't charging.  It isn't the battery, but could be something other than the alternator--wiring, regulator, breaker, etc.

[flight2000]

Yep, went through this last month.  I had a mechanic come out with the equipment to isolate the electrical system and alternator to see what was and what wasn't working.  Mine turned out to be the alternator.  He was shocked to learn that it was 12 years old.  Appearently, alternators have a very short lifespan (he said 2-3 years on most he's seen).

Brian

[M016576]

really, only 2-3 years on the alternator?

I'm curious what other people in the forum have seen on their alternators?

[N6843N]

I still have the original alternator in my airplane, amazing what a little maintenance will do for ya. I replace the brushes and inspect it for bearing wear every 3 years. Surprized no one has mentioned the easiest and most  obvious,...drive belt.

[laytonl]

In 30 years of airplane ownership, I've found alternators last about 1,000 hours.  Occasionally have to change diodes at 500 hours or so.

Lee

[scottfromiowa]

I'm still a generator guy.  I have replaced BOTH the belt AND generator since purchase, but believe the generator was NEVER replaced prior to mine and that was 1900+ hours and 36 years!  I also replaced the voltage regulator when I installed an HID landing light.  The EI voltmeter is between 11.7and 13.3 (volts) in cruise and shows discharge while taxing under low power.  I LIKE knowing what's going on with the EI digital indicator.  Also fun to see what everything is drawing by switching to "amps".  The HID landing light is amazingly efficient in current draw and reduced heat over OEM landing light...besides being WAAAAaay brighter and having amazing lifespan.  i cruise with landing light ON.

[Alan Fox]

I have an Interav alternator conversion on my B model that is over 20 years old and runs fine , If you have a problem that cant be fixed with brushes or diodes , I recommend the Plane Power replacements ...  They are actually Toyota (nippondenso)   alternators that are STC'd conversions for aircraft , They are a lot lighter also....

[jlunseth]

Not all Mooneys have a drive belt.  Some are direct drive (the 231 in particular) and the clutch can go out in the drive unit so the alternator stops spinning.

[flight2000]

Hey now, don't shoot the messenger...   Jut going off what he told me.  I've only owned the aircraft for 7 months now and I'm learning on the fly.  It's been a very educational 7 months and I've scoured my log books and noted when all of the major items were replaced in a simple spreadsheet.

Brian

[Mooney13]

So.....It turned out to be a wire from the back of the alternator...I am not sure which one, but it had broke loose from the connector. So they cut it and added a new connector and I'm back in business.... For once it was good news (kind of) ... I guess that makes the winner of the dilemma the ALTERNATOR!

Thanks as always for the advice from all!

[Jeff_S]

Hey Joe. Glad it was an easy fix. Based on your description that's certainly what it seemed like. If you are seeing a drain on the battery and eventually get the low-voltage warnings, it's because your alternator is no longer handling the electrical load and your battery has engaged to keep things going. That's pretty standard practice in a single-engine plane. The SOP in that instance is to try to reset the alternator (check the breaker first, and then flip the Master off/on) and if you still have the same problem, reduce electrical load as much as possible and make sure you save enough juice to drop the gear!

I don't mean to sound pedantic, but I just point all that out because it's exactly what I DIDN'T do the first time I had an alternator go bad in flight (on my first solo x-country, no less). Luckily I was in a fixed gear plane and I had just enough radio to talk to an airliner who relayed my request to the home drome and was cleared to land from 50 miles out. But that gave me cause to really understand how the electrical system works in a plane.