Check the condition of the electrolyte (acid) during charging. A shorted cell will not "gas", (form bubbles in the acid as the battery charger operates). If a cell is shorted, the other two cells will gas violently because they're not able to create enough resistance to control the charging current.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!