I have a 01 Duramax with Alli. Started my truck SES light came on. Stopped at Home Depot for 1 1/2 hrs. Got to my truck and dead, no click of starter, nothing worked, not even the remote locks, wasn't even sure it was my truck at first. Took it to Chevy they had it for a couple hours and I got a call saying both of my batteries took a dump. Truck has 47000 no power adders. Is it strange both batteries were bad. They said battery didn't even register on their meter. Didn't want to pay $380 for 2 batteries I bought them from a local auto parts. Cost me $250 for some gel batteries. Had to pay for their $100 diagnostic charge. Stuck one of the batteries in Started made it home. Got home 1.5 hrs later went to switch the other battery completely dead again. Switched battery started fine. Gauges say 12 volts roughly. What could be my problem.

Thanks

Nate

If those were original battery's, you got more than your monies worth. With dual batteries, if one goes bad it will take the other one with it. Now that you have both new batteries you should measur more than 13 volts ( mine reads 14 volts chatging). After battery's are fully charged, you should reAd about 12.5 volts after the surface charge is bured off. You do that by (engine turned off) turning thne head lights on for about ten seconds. Use a digital meter. A reputable battery source will usually test your system for free. SAM's here gets $110 each for OPTIMA battery's. If youn use a smart (all electronic/automatic)charger at home you have to mcharge the battery's one at a time( the ground discopnnected on one of then battery's. Hope this helps you.

If battery's discharges again you have other trouble, like something shorted or runing without being turned on.