Loaded vs unloaded battery test

[mbplace]

Been having battery issues - ran a charging test and my unloaded reading was 19.4 while my loaded was 12.4. What could be causing that? Faulty alternator or wiring? Seems odd to me that unloaded would be higher than loaded? Having a hard time diagnosing the issue

 

[charliemeyer007]

I don't understand un loaded terms. Your battery with nothing connected (un loaded?) should be at least 12.6 when charged. While charging it should read 13.6 to 14.4. You should never see 19 volts. I'd say voltage regulator has issues?

Batteries these days are crap. Load test the battery. Clean and inspect the terminals/post and the wires on the alternator and battery.

This is for lead/acid battery - your reading for other chemistries could be different. Not all voltmeters read the same.

 

[B y r o n]

Are you testing your alternator or battery? Sounds like alternator to me. No load on the alternator shows charging voltage but with load, things like lights and accessories turned on, available voltage out is lower.

 

[mbplace]

I don't understand un loaded terms. Your battery with nothing connected (un loaded?) should be at least 12.6 when charged. While charging it should read 13.6 to 14.4. You should never see 19 volts. I'd say voltage regulator has issues?

Batteries these days are crap. Load test the battery. Clean and inspect the terminals/post and the wires on the alternator and battery.

This is for lead/acid battery - your reading for other chemistries could be different. Not all voltmeters read the same.

I’ll recheck but I read that at idle it’s reading over 19 and about 2500 rpm’s it’s down to a normal range - it was a charging test. Internally regulated alternator

 

[rlong]

…ran a charging test and my unloaded reading was 19.4 while my loaded was 12.4. What could be causing that?

The “Load” (smarta$$ comment). Yes, sounds like unloaded alternator voltage (and some will say that will cause damage to alternator if run for a period of time). Test are generally at battery not running, and running..

And the quick field test if your alternator is working is to remove the positive terminal on battery and see if the vehicle continues to run (it should with functioning alternator.)

 

[mbplace]

Definitely seems like the regulator is malfunctioning - at idle it’s close to 17v and climbing. Thanks for the info here internal regulator in the alternator must be malfunctioning

 

[rlong]

That’ll cook the battery pretty quick..