Operator’s Manual Vehicle Maintenance CXU, CHU, GU, TD, MRU and LEU 43 Completely Discharged Batteries Extremely cold or completely discharged batteries may not initially show a charge since the electrolyte is nearly pure water and, therefore, a poor conductor. As the acid level in the electrolyte increases during charging, the charging current will also increase. Use the following procedure when charging a completely discharged battery: 1 Measure the voltage at the battery terminals. If it is below 10 volts, current will be very low and may not show up on many battery charger ammeters. 2 Set the charger on the high setting.
3 Some chargers have a polarity protection feature which prevents accidental reversal of the charger leads. A completely discharged battery will not have enough voltage to override this feature, making it appear that the battery will not accept a charge. Check the charger manufacturers instructions on how to bypass this feature. 4 Once the battery starts to accept a charge, the charging rate will rise very rapidly. Carefully monitor the ammeter to prevent too-high a charging rate. 5 Proceed to charge battery at one-tenth of its rated capacity for one-half hour. Example: For battery rated at 64 (amps-hour), charge at 6.4 amp setting. Note:
Batteries with very low voltage (below 11.6 volts) or those that do not initially accept a charge are not necessarily defective. Batteries that have been discharged for long periods of time may be heavily sulfated or hydrated (containing lead shorts that cause the battery to self-discharge). To accept a charge, batteries with either of these conditions may require a longer charging time or a very high initial charge. Use the following chart to determine the time required for the battery to begin accepting a measurable charge.
(If the battery has not started to accept a charge after the specified time, it should be replaced.) Charger Voltage Hours 16.0 or more Up to 4 14.0 to 15.9 Up to 8 13.9 or less Up to 16