Charging problems when warm

[Shaman]

Cold Idle - 13.9-14.2
Warm Idle - 12.5-13
Moving - 13.5(lights, WMI, etc)-14.3
Engine off - 11.5-12.5

I understand that my battery is bad, and I will try to replace it this weekend. Car doesn't have a problem starting in freezing temps, just wondering if the battery was the cause of the low warm idle voltage, or if I need to get the alternator checked out too.

 

[Chris142]

I don't see anything wrong with your numbers but if the battery is bad you can't diagnose any electrical problems.

 

[JHZR2]

Nothing wrong, alternator will adapt to battery state of charge, load and temperature.

But going around with a bad battery will harm your alternator. and leave you stranded.

 

[Shaman]

What I meant to say by I know the battery is dead, is that I assumed that the battery was bad. Doesn't the 11.5 mean that the battery is bad? That was sitting at the gas station with the engine off for about 5 minutes with nothing but the radio and gauges on.

 

[toyota62]

When alternator is cold 14.5-15.5V is normal.
At operating temp above 13V is ok.

 

[Chris142]

Originally Posted By: Shaman
What I meant to say by I know the battery is dead, is that I assumed that the battery was bad. Doesn't the 11.5 mean that the battery is bad? That was sitting at the gas station with the engine off for about 5 minutes with nothing but the radio and gauges on.
Sounds like it. Whats the voltage 20 minutes after parking it with nothing on?

 

[EricF]

voltage numbers look fine.

Get an ammeter and disconnect the negative battery cable. put ammeter inline. How many amps are being drawn? If over 300ma, you have a parastatic draw and need to look into that.

the car computer and clock/radio take a sneeze amount of power, and if you have an alarm, same thing. combined these should exceed 300ma.

 

[Shaman]

Would a voltage tester work? I think it had amps. Just didn't know how to use it right.

 

[Shaman]

3 hours off
12.05v dropping to 11.97 in the 15 seconds the key was on engine off

 

[Jonny Z]

It has a partial short in a cell from sludge getting between +/- plates. But don't try AutoRx on this one.

Get a new one.

 

[AdRock]

Definitely get a new battery before it starts to overwork the ALT and you end up having to replace both.

 

[Shaman]

sorry, I pulled out the multimeter, but don't know how to use it for amps (never had a shop class, and dad didn't ever show me).

 

[Gary Allan]

As was suggested, take off one of the terminals (off the post) and measure between the post and the terminal.

 

[Shaman]

Battery got replaced. We shall see how things go. Friend's car just sprung a major internal oil leak. Look for a new post.

 

[mechtech2]

Alternators [now called AC generators!] have a built in voltage regulating system dependent on ambient temperatures.
You get more voltage when cold than hot.
But sometimes this is by natural electronic coincidence, not a regulator. It is a natural phenomena that works about the same.
REsistance goes up in the coils and other parts when hot, and less voltage is produced.
This is great for more cold weather Vs when you need it, and less in summer when you can overcharge.