I have a couple of questions:
Why the side of a battery is bulging?
Is a battery with a bulging side ruined?
The bulging is caused by gassing. This is caused by overcharging or by a short circuit inside the battery. The acid inside the battery is turned to gas and it expands the sides of the battery.
to the question ... is it ruined? .... i would consider buying a new one ASAP ... shop around, there are places that "rebuild" batteries and sell them much cheaper than retail ($25 and up)....get in the yellow pages and start calling around...
This is initiated by cheating or by a short out inside the electric cell. The harsh corrosive inside the electric cell is turned to gas and it grows the sides of the electric cell.
Choose those battery which has long term capacity for working and reliable in every type of conditions.