Battery Not Charging

[Saville]

Started up the other day and when I ran my run-up check to turn various lights on and off to watch the amperes change I noticed that the voltage was low and the amps were not reading the usual 6+ when no lights were on and not the 14 or so when the lights were all on. It was reading more like 1-2.

So there seems to be a problem with the charging system.

Yesterday I:

1) Put the battery (Odyssey PC925) on the Odyssey charger and it was charging.
- I installed the PC925 in 2016. It has worked great ever since. The engine starts don't drag at the beginning.

2) Removed the cowling and looked at the alternator:
- Belt was tight and in good condition.
- Alternator had no obvious visual issues
- Connections coming out of the alternator were tight.

So that's the simple checks. I now have to check the connections at the battery end.

My question:

Is it possible that the battery would recharge on the Odyssey charger but NOT with the aircraft system ( assuming the aircraft systems are fine) because it's so old?

 

[D-Dubya]

There are some good articles in Kitplanes about troubleshooting your electrical systems. I printed one out and it's at the airport, otherwise I'd provide that reference.

I'm not enough of an expert to answer your question, but I can say if you got eight years out of a battery, you're doing pretty good. Not saying that's necessarily the problem, but it's near the end of its service life.

 

[Saville]

Well I just ordered a new battery. Whether or not this is the problem I think it's time for a new battery.

I will install it and then see if the problem persists.

 

[Carl Froehlich]

Is your amp meter shunt on the alternator output or on the battery output?

While amps going one way or another is nice to know, the battery really only cares about buss voltage. As yours was low this alone is cause for your battery not charging.

But - considering your current battery is way past it due date, I suggest your first check is to measure the battery terminal voltage with no load (master off). If low, then you have at least one dead cell. If you measured battery terminal voltage after you took it off the charger you would know the health of your battery.

Carl

 

[bjdecker]

Expanding on Carl's comment - Charging is accomplished by the buss voltage (alternator output) being higher than the battery voltage. There isn't a separate/discrete charging system.

Ergo, If the alternator is not working (no field current: either a blown field breaker, or failed diodes, failed regulator, broken belt, etc.) the battery will not charge.

 

[ljpappas]

The usual culprit is the voltage regulator. But your battery is old. I never get that long from a PC680 here in Phoenix.

 

[Thermos]

Hey Gregg -

No harm in replacing the battery...an 8-year-old PC680 doesn't owe you anything at this point. But as the other folks have said, your symptoms suggest an alternator or voltage regulator problem. Is your regulator separate from the alternator?

Dave

 

[Saville]

Ok so today I replaced the battery. I started up in order to see if it was the battery that would not charge. lo and behold.....the alternator circuit breaker had popped (Note to self - better check the circuit breakers if there's an in flight issue). Pushed the breaker in, started the engine, everything works fine - amps go up as I put loads on the system just like normal.

So....the question has changed.....

What would cause the alternator circuit breaker to pop? It's 45 amps.

 

[Carl Froehlich]

What would cause the alternator circuit breaker to pop? It's 45 amps.

Odds are you have a 60 amp alternator. A low battery will draw a lot more than 45 amps.

Carl

 

[blaplante]

Odds are you have a 60 amp alternator. A low battery will draw a lot more than 45 amps.

Carl

If so... the question becomes, what gauge of wire is running from the alternator to the breaker, and on to the main bus? You may need to up the wire gauge and replace the breaker.

 

[Saville]

Odds are you have a 60 amp alternator. A low battery will draw a lot more than 45 amps.

Carl

Ah I bet that's what it was - thanks.

 

[dmattmul]

Odds are you have a 60 amp alternator. A low battery will draw a lot more than 45 amps.

Carl

How did you come to that conclusion? I am not sure where this CB was located but they are temperature dependent and prone to failure FWF. I have seen and helped many builders with faulty CBs after a few years FWF. When I looked into a ANL fuse, or a CB for my B lead most CBs were rated at 70 C or lower. (158F) If they are not located in the upper part of the FWF easily exceed this temp. Even ANL fuses which are fairly robust suffer from temperature degradation but follow a tested temp vs % life curve.

The OP needs to find out his alternator size, wire size and make an informed decision how to proceed and not guess at these parameters.

 

[Saville]

How did you come to that conclusion? I am not sure where this CB was located but they are temperature dependent and prone to failure FWF. I have seen and helped many builders with faulty CBs after a few years FWF. When I looked into a ANL fuse, or a CB for my B lead most CBs were rated at 70 C or lower. (158F) If they are not located in the upper part of the FWF easily exceed this temp. Even ANL fuses which are fairly robust suffer from temperature degradation but follow a tested temp vs % life curve.

The OP needs to find out his alternator size, wire size and make an informed decision how to proceed and not guess at these parameters.

I came to that conclusion because I flew, waited a couple hours, got back in the plane, went to start....and the Master was on. Surprised me. But the plane started right up.
And I'm the OP