yeah that's not the original ni-cad battery, but should be replaced just the same
check here: https://www.pinwiki.com/wiki/index.php?title=Bally/Stern
there appears to be possible leakage thus damage to the lower section of the board, and that larger resistor, the 82ohm one looks bad/cooked, but it could be the pic.
need some more close up pics of the lower section, with the battery removed.