My house banks is 4 Exide GC -110 batteries. They are ~6 years old. One of them is failing. The buildup in the pic suggests it has a crack in the case where corrosive gas is escaping.
The bank is functioning well otherwise.
Is it OK to replace the one battery that is failing? If so is there anything that I need to do to "equalize" or "re balance" them?
Or must I bite the bullet and replace all 4 at once?