Battery is approaching the end of its service life. Specific gravity, as read at the end of the duty cycle, is an excellent indication of the amount of battery capacity that has been used. Battery manufacturers provide graphs for all batteries in their product lines to translate specific gravity into depth of discharge. As the cells discharge, electrolyte specific gravity reduces at slightly different rates for different-sized plates. Modern, electronically-controlled battery chargers comprise refined controls to ensure that the battery is safely charged to the proper level within the allotted charging time.
Chargers can, however, get out of adjustment.
Any of the following trouble signs indicate that the charger might be in need of adjustment. Unusual rise in battery temperature. The temperature of a battery undergoing charge should not rise more than 25 degrees F during an eight hour charge period. A higher temperature rise might mean that the charger is out of adjustment. Continuous running of charger.