My dads 2016 LML has been turning over a little on the slow side for a while, but this morning it wouldn’t turn over at all. I jumped it with another vehicle and checked the battery voltage with it running after the jump vehicle was disconnected. It was reading in the mid to upper 14’s on the multimeter. I thought ok, it needs batteries... so I take them off and go get new ones.
I ended up getting the Everstart Maxx AGM H6 batteries at WM for ~$150 each. I checked the resting voltage before I installed them, both were at 12.6-12.7 volts.
I got them installed and started the truck up, all seems well until I throw the multimeter on it and find that it is charging at 15.3 volts. I let the truck run for about 30 minutes and the voltage did drop to ~14.5 volts for a minute and then went right back to 15.3 volts.
This truck was manufactured in 8/2016 so the factory batteries were only 3 years and 3 months old. I thought it was odd for them to be dead at just over 3 years old, but now I’m wondering if the charging system/alternator is overcharging and cooking the batteries?
The truck has 48k miles and ~3,300 engine hours. I did not have the old batteries load tested before replacing them but the truck jumped easily and I did verify that the alternator was charging before I removed them so I am confident that at least one of them was bad.
I did check for codes and the only thing it’s showing is a P21DD for the DEF heater. No pending codes.
It runs great and doesn’t have any other symptoms of anything being wrong. I’m just concerning about it charging at 15.3 volts, that seems way too high to me. What do you guys think?