TM10-3930-660-20 8-43. BATTBRIES    - SERVICE/TEST/RBPLACE (Cont’d) TESTING WARNING Never disconnect any charging unit circuit or battery circuit cable from battery when the charging unit is operating. A spark can cause an explosion from the flammable vapor mixture of hydrogen and oxygen that is released through the battery outlets. Injury to personnel can result. The battery voltage test can be done on the engine. If the on-engine test shows a defect, remove batteries for further testing. Refer to STE/ICE battery voltage test, para. 2-13. For additional testing requirements refer to TM9-6140-200-14. 8-113