Any ideas why I keep eating batteries?

CAT279C with 5000 hours. I’ve had the machine since 4600 hours and I’ve gone through 5 CAT brand batteries. I’ve put in a battery disconnect switch, replaced the alternator to no avail. Every time I get a new battery, it lasts maybe 15 hours and then it acts like a dead battery and will only start with a jump. Battery reads 12.6 volts sitting in the machine, and my battery tester says there is a “surface charge” when it’s in the machine and when out, it says it’s a bad battery with only...

Any ideas why I keep eating batteries?