I replace ALL my batteries ever 5 years no matter what. Sounds to me like it's dealer time...lol
One thing I always do is I install a master disconnect on the NEGATIVE post of all my starting batteries unless I have them on a trickle charger when parked. If you break the electrical circuit and the battery sits all winter with no parasitic load on it, your ECM is always drawing power, the battery will retain almost all it's power for a long time.
I read somewhere that a starting battery retains it's power (when charged fully) and sitting but out of circuit, it looses about 5% per month and a dead batter in the winter will freeze if it's below freezing and once they freeze, they are basically shot. I a fully charged battery can withstand 40 below no issue.
Batteries, like everything else today, ain't cheap, especially the Group 31, 1000 CCA ones I use. I keep my diesel pickup truck and the side by side on a battery tender all winter. I only use Interstates and I buy them from a local truck dealership because they have high turnover. All wet charged batteries when sitting on the shelf are using up their useful life. I never buy any batteries if the top is dusty, a sure sign they are old and getting feeble and when I replace them, I always trickle charge them before installing as well. They will all need to be 'topped off'
