ok so i am in need of a new battery. i have one that is about a year old and still under warranty and its cca is 700 or 750,and the other is the same but out of warranty. the other day i was reading and saw some guys say you need 850 cca or more. well i have a hell of a time getting the truck to start when the weather is 32 or below. it acts as if the battery's are dead but when the temp raises it will start even without charging the battery. I can go crank at it, at 32 below and it will be slow to turn over then just eventually die and do nothing, come back that afternoon when the temps go up to around 45 and she will fire off. so my question is i was going to replace the one bad battery i have b/c i know it is bad anyways (wouldn't accept charge) but i was going to replace it with a bigger battery such as one with a 850cca. would this be ok to put with the other battery that has a lower cca? im in a delima b/c the other battery is under warranty and i don't have the cash to drop on 2 new battery's. so i got two options, replace with one just like it or replace with a bigger one if it will be ok. what do you guys think?