After my cars sits for 3 days I have a dead battery condition. Walmart claims the battery is good.

Here is what I found. After charging the battery it has 12.51 volts. When running at idle the battery reads over 14 volts. The drain is 0.02 Amps which I suspect is fine.

I'm concluding that the battery is in fact bad. There is just one way that I can think of where the battery is good....

Is it possible that while the car is sitting that the drain jumps from .02A to a higher draw?

Thanks,
Jomo

 

Most auto part stores will test the battery for free but you have to leave the battery with them for a hour on their test stand .

Full battery charge is 12.77 volts

If you can't charge to 100 % then that is an indication alone you have a bad battery not taking a charge

 

Good test is to remove the battery from the car when charged, let it sit for 72 hours alone and look at the voltage drop. If your getting 12.7 down to 12.4v in three days or something then clearly a bad battery. I have a second car that sat for 4 weeks with a new battery, started first time on the key.

 

I tried this overnight and did see a drop in voltage. I just came back from Walmart with a new battery. They really did not want to replace it but I insisted. The new battery has a higher voltage- .5V higher! I think the problem is fixed.
Thanks!

 

hmm