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I want to second what repairman54 just said. I replaced my AGM about a year ago on my 2014. It showed a reduced life on my battery tester and had been in there for 7 years--it was time.

The battery charged at 14 or over for a day or so after installing. Then it started running at 12.6, 12.4, and even 12.3 at times. I am not an expert on the logic in the charging control computer, but a brand new battery checks at over 100% life on my tester. I believe after a short charge period upon restart or sitting with lights on and engine not running, the battery is sensed at being charged and the system drops to a maintenance amount of current flowing just to replace what is being used.

I also read that the system does a drawdown to sense the condition of the battery. That might occur after the car has been shut down. But I also wonder if the lower readings while running were that the system is charging the rear AGM battery and the front battery is supplying power to the running engine with no replenishment from the alternator while the alternator is chargin the rear battery.

I too was intrigue in earlier days when on longer drives with the original battery I would find the car running at 12.6 or so. Then the replacement
battery really intrigued me. But if you have no other symptoms, I'd just be happy. I do want to comment that I would notice after the stop-start has been activated for short to long times, the voltage would jump back up to the 14.6/14.4 range for a couple of minutes, replacing what was drained while the engine was off but the body is using low power along with a transmission pump and a coolant pump, if I have that right. Watching the voltage during stop-start, if the voltage drops to 2.2 or 2.1, the car restarts to keep from draining the battery too much, and I found that true.

My battery was a Walmart and I had to go 40 miles to a Walmart that carried the AGM. I was told most Walmarts would get the AGM batteries. Finding a store that had them was tricky using their inventory search method. I had to input various zip codes to have the website find a Walmart "near me" with one in stock.

I recommend turning the DIC back to tire pressures, because I was becoming neurotic about the voltages on the new battery. LOL
 
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