Battery light came on then truck died. I know I am due for a new battery anyway. Truck started the next day so I pulled it to the garage and cleaned and charged battery. I started the truck and turned the lights on and let it idle' After about 20 mins. the battery light came on until I revved the engine. Long story short with truck off I read 12 volts at battery. With truck running I read 15 volts at battery. Is 15 volts a little high? Could it be overcharging. Thanks. 05 5.4

 

15 volts is a bit high and 12 volts is a bit low. Are you using a digital meter and reading the decimal points? Go to a parts store and get the battery and alternator load tested.

 

Yea my battery is about 10 years old so I am going to put a new one in. I just didn't want to overcharge a brand new battery. I was using my fluke voltage tester I have for work. I need to go buy a new multi-meter. I read somewhere it should normally be about 14.7 while running.

 

13.7 to 14.8 is normal. 15.0 shouldn't damage anything, but anything higher is not good.

 

I found that when the battery in my multimeter is weak, it reads the voltage higher than it should. I found out when my battery was measured at 18volts. I checked a battery in another car and it also read 18 volts. I replaced the 9 volt battery in my meter and it read correctly again. So, check or replace the battery in your meter and see if it still reads 15 volts when running.