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Over the past few weeks, my batteries have been going dead, rather quickly; overnight. I had them tested, and they tested fine (although that day and the day prior, they were doing fine) then a few days later they've died again. I havnt been able to check if there is a drain on the system yet, so last night I disconnected one of the batteries after driving home from work, so I would have one good battery in the morning even if there was a drain. I know the truck will start with just one healthy battery. Welp. No start. That battery was dead too. Can anyone help me figure this out? It's possible that the isolated battery didn't charge long enough on the 5 minute drive home from work, I suppose.
Are you certain the charging system is functioning properly?
I've had it tested twice, and both times it passed. Also, once the truck is on it has no problem holding 13.8-14.0v.
AAA came out this morning after I posted and tested my batteries, and the alternator. The first battery he tested came up at 105CCA of a rated 850CCA. Last week when I had them tested, they tested okay. It seems to be an intermittent issue.
How old are you batteries, did they load test them?
They are a year old. I'm not sure exactly what a load test is. I did a load test today, but I think it was for the alternator? With the truck running he turned on all of the accessories and rev'd the truck and checked voltages.
Have you checked to make sure there isn't a light on? My step kids are bad about messing with the lights and forgetting to turn them off. They have left my wife with a dead battery on more than one occasion.
turning on all the accessories and reving it up and checking voltage is NOT a reliable test, I would not use that person again! A load test puts a large resistive load on the batteries, they should be tested one at a time, not connected together. With the proper equipment you can also accurately load the alternator to check its voltage versus amp output.