I have a Tundra and the "temperature compensating" was causing issues charging my AGM due to the constant low voltage. There are a lot of threads on the Tundra forums with people that have the same issue, some people were actually putting there truck on a charger every night to top the battery up. They ended up finding that Toyota use one of the fuses to detect the voltage that regulates the alternator output, they put a diode inline using an add-a-fuse holder to increase the voltage. I ended up buying a replacement fuse that had the diode in it to trick the alternator. A company in Australia makes a couple of models, two are a fixed voltage increase and the other has an adjustable voltage increase. I bought the adjustable one, but honestly I haven't changed it since I got it and the setting I ended up using I think is the same voltage increase as the non-adjustable ones. I was a little leary about ordering something from Australia, but it arrived almost 30 days later. Here is their website if your interested,
https://www.hkbelect.com/products/toyota/?model=tundra&year=2012