This is frustrating and a bit strange to me. My '21 Tacoma Off Road came with a barely adequate battery, a Clarios 582 CCA Group 24F. I use it mostly for towing a small camper and light "Off Road" (really on slightly rough road and a couple of beach surf fishing trips). Anyway I noticed the "Check Charging System" message popping up when I first got it and was told by the dealer that it just meant the motor wasn't running and I was draining the battery so I should just turn the car off so as to not drain the battery too much. OK, so I buy a multimeter and start digging around. After two years and only 16K miles of towing/camping/light off roading, and turning electronics off as soon as I can after the motor stops running, I find by my meter a reading of 12 volts after sitting overnight. So, I think my lead acid OEM battery is getting weak and I start looking for a replacement because I like to stay ahead of problems and I know what it's like to be stuck out in the boonies with a dead battery. It wasn't any fun. Toyota for some reason (I suspect money) decided to put a low capacity non-AGM battery in their "Off Road" built for towing and the AC outlet in the bed, truck. Searching around on the internet I read that the deep cycle AGM ideal batteries require more voltage than my vehicles alternator puts out. Figuring my dealer would know what to do I talk to the service rep. at my last free maintenance that came with the truck. He doesn't want to sell me a Toyota TrueStart battery. Instead he offers an AGM battery branded by someone I never heard of for $239 plus tax. When I mention that my alternator only pushes out 13.6 volts and I've read that's not enough to fully charge an AGM battery he doesn't seem to know what I'm talking about. So thinking that maybe I don't know what I'm taking about I go home and do more digging on the internet. Several places I read that on 3Gen Tacomas the alternator voltage delivery is controlled by the ECU. I had mentioned that to the dealer service rep and he told me the alternator voltage is not controlled by the ECU. Who do you think is right? Isn't it strange that for the most popular small truck in the USA there doesn't seem to be a straightforward answer as to how to best replace the battery? Maybe if I keep my battery on a trickle charger I can squeeze more use out of it without getting stuck and the answer will seem clearer later. If I need a tune to boost the voltage output of my alternator would that void my Toyota warranty? Any insight into this issue will be greatly appreciated.