There are three main possibilities here;
1. The old battery had a faulty cell. If that caused the problem then Dockhead is right - a new battery will fix it.
2. The charger is faulty and is pumping amps into an already charged battery. To put it another way, the charger could not sense when to switch to float mode and lower its output. Because your charger cannot be adjusted a new one might be necessary.
3. Two battery cables
are touching and causing the short. This is less likely but you never know.
The only thing to do is connect the new battery, switch on the charger and see what happens. Assuming that the other batteries are fairly well charged then bringing the bank up to float mode should take something like an hour. You can sense the state of the new battery just by touching it. It should feel a little warm but not hot. A charging
battery is likely to be around 85f/30c. You can also put a voltmeter across the battery terminals. I don't know the automatic settings but the system should switch to float mode at 14v or a little above.
Hopefully the float indicator light will come on and the problem will be solved