· Super Moderator
first things first, is that a diesel motor? Just trying to figure out why you have 2 batteries, and if it's factory. Secondly, there may be a problem with your other battery that is causing the first one to take the load and get killed. For the most part, vehicle batteries should be replaced together, preferably from the same brand, bath, and week of batteries to make sure they are matched. Disalike batteries due to age, brands, etc can cause the other batteries in the bank to prematurley fail... Hope this helps.