Failure of one or more cells to rise to  the required 1.55 volts at the end of  charge Negative electrode not fully charged Cellophane separator damage Discharge battery and recharge. If the  cell still fails to rise to 1.55 volts or if  the cell’s voltage rises to 1.55 volts or  above and then drops, remove cell  and replace. Distortion of cell case to cover Overcharged, overdischarged, or  overheated cell with internal short Plugged vent cap Overheated battery Discharge battery and disassemble.  Replace defective cell. Recondition  battery. Replace vent cap. Check voltage regulator: treat battery  as above, replacing battery case and  cover and all other defective parts. Frequent addition of water Cell out of balance Damaged “O” ring, vent cap Leaking cell Charge voltage too high Recondition battery. Replace damaged parts. Discharge battery and disassemble. Replace defective cell, recondition  battery. Adjust voltage regulator. Corrosion of top hardware Acid flumes or spray or other corrosive  atmosphere Replace parts. Battery should be kept  clean and kept away from such  environments. Foreign material within the cell case Introduced into cell through addition of  impure water or water contaminated with  acid Discharge battery and disassemble,  remove cell and replace, recondition  battery. Trouble Probable Cause Corrective Action Apparent loss of capacity Very common when recharging on a  constant potential bus, as in aircraft Usually indicates imbalance between cells  because of difference in temperature,  charge efficiency, self-discharge rate, etc.,  in the cells Electrolyte level too low  Battery not fully charged Reconditioning will alleviate this  condition. Charge. Adjust electrolyte level. Check  aircraft voltage regulator. If OK, reduce  maintenance interval. Complete failure to operate Defective connection in equipment circuitry  in which battery is installed, such as broken  lead, inoperative relay, or improper  receptacle installation End terminal connector loose or diengaged  Poor intercell connections Open circuit or dry cell Check and correct external circuitry. Clean and retighten hardware using  proper torque values. Replace defective cell. Excessive spewage of electrolyte High charge voltage High temperature during charge Electrolyte level too high Loose or damaged vent cap Damaged cell and seal Clean battery, charge, and adjust  electrolyte level. Clean battery, tighten or replace cap,  charge and adjust electrolyte level. Short out all cells to 0 volts, clean  battery, replace defective cell, charge,  and adjust electrolyte level. Figure 9-39.  Battery troubleshooting guide. 9-28