Is this a battery or alternator issue?

[GasX]

I made a quick run a mile down the road where I have some chickens in a pasture to collect eggs. I left the engine running and when I got back in the car I noticed the radio turned off.

I looked at the dash and the battery light was on. I revved the engine and the radio went back on but the battery light remained on and stayed on until I got home.

The vehicle in question is a 2006 Honda Odyssey and occasionally interior lights can be left on, so running the battery down does happen. If the battery was REALLY low and starting dropped it to a critical level would these symptoms potentially occur until the engine ran long enough to charge it back up or should the alternator generate enough current to have everything function fine with the engine idling?

Anything else potentially happening here?

 

[yottabit]

should the alternator generate enough current to have everything function fine with the engine idling?

Yes, it should.

Kind of tricky to separate though, as the battery also serves as a bit of a capacitor for the alternator. When you revved the engine the power came back in which means the alternator is working at least partially

How old is the battery? Lots of places do free battery and sometimes alternator testing.

The only other "potential thing" that could be happening is some electrical/grounding issue that's draining down the battery. But I don't see any reason to think that's true in your case

My experience:
Really bad battery, Good alternator = You jumpstart the car and can drive wherever mostly fine, if it dies on you you need another jump start

Really bad alternator, Good battery = You can charge the battery overnight and drive short distances before it dies

You sound like you're somewhere in between which is kind of tricky to diagnose.

I just re-read your post and you said you only drove it about a mile back home, that definitely wouldn't be enough time for the alternator to recharge the battery from a really low state. So you may have no problem at all, just drive it down the highway some and see if it recharges. Or charge the battery overnight with a battery charger.

If it's the originally battery then I would lean towards the battery just because the failure rate on those is quite a bit higher. Sounds about right that the battery on a ~9 year old car would be shot to crap. However if it's fairly new then I would say the problem is most likely your alternator.

You'll know quickly if you replace the battery and still have problems that it's the alternator. That's my general course of actions for these things, replace battery first (easy and probably should be done anyway), replace alternator if needed. That being said the only time I've experienced what you're describing, is when I've had a bad alternator.

 

[pauldun170]

I made a quick run a mile down the road where I have some chickens in a pasture to collect eggs. I left the engine running and when I got back in the car I noticed the radio turned off.

I looked at the dash and the battery light was on. I revved the engine and the radio went back on but the battery light remained on and stayed on until I got home.

The vehicle in question is a 2006 Honda Odyssey and occasionally interior lights can be left on, so running the battery down does happen. If the battery was REALLY low and starting dropped it to a critical level would these symptoms potentially occur until the engine ran long enough to charge it back up or should the alternator generate enough current to have everything function fine with the engine idling?

Anything else potentially happening here?

Sounds like either the alternator or a belt broke (if you also overheat)

 

[GasX]

The serpentine is intact, but there was a lot of belt squeal the other night

 

[LTC8K6]

An alternator diode failure can make weird stuff go on in a modern vehicle.

Can you check the voltage at the battery with the engine running?

If you have an Auto Zone or similar near you, they will usually check your battery and charging system for free.

 

[GasX]

Autozone tested the car and said the battery AND the alternator are bad...

The battery was replaced on warranty, but I have to take it into the shop to have the alternator looked at...

 

[LTC8K6]

Well, that's certainly possible.

Do you let the battery run down frequently?

Doing so is bad for both the battery and the alternator.

 

[Triumph]

A bad battery can absolutely cause electrical problems even if the alternator is putting out a strong 14.5 volts. But sounds like you at least solved the battery problem with a warranty.

The alternator is easy to check with just a voltmeter. Should be over 13 volts at idle and over 14 when the RPM's are up. Turn EVERYTHING on, and if it still puts out those numbers, it is good. Note that sometimes the alternator itself is just fine, it's the regulator that can go bad. These voltage numbers are approximates, I don't know what your car specifies as targets and what your battery likes to see, but these numbers should be good enough to diagnose.

 

[GasX]

Well, that's certainly possible.

Do you let the battery run down frequently?

Doing so is bad for both the battery and the alternator.

not intentionally, of course, but my small children often leave reading lights on or doors open and the battery gets drained about twice a year by accident...

 

[LTC8K6]

The owner's manual says that if the "battery" light comes on, it means the battery is not being charged. That is, the alternator has taken a vacation.

 

[LTC8K6]

not intentionally, of course, but my small children often leave reading lights on or doors open and the battery gets drained about twice a year by accident...

Yeah, that's not enough to worry about.

Basically, the battery was not designed to be repeatedly deeply discharged, and the alternator was not designed to repeatedly recharge a dead battery.

Once in a while is not a problem.