Totally Discharged Batteries, Charging
- Batteries which have not been used for lengthy periods, e.g. in vehicles which have not been driven, are subject to self-discharge.
- Batteries are considered to be severely discharged if open-circuit voltage drops below 11.6 V. With voltage between 12.2 and 11.6 V, the battery is pre-damaged. Measure no-load voltage:
- Vehicles without Energy Management Control Module J644 → Battery No-Load Voltage - Vehicles without Energy Management Control Module, Checking .
- Vehicles with Energy Management Control Module J644 → Battery No-Load Voltage - Vehicles with Energy Management Control Module, Checking .
- With severely discharged batteries, the electrolyte (mixture of sulfuric acid and water) is mostly water, with a greatly reduced sulfuric acid content.
- Severely discharged batteries become sulfated, i.e. all the plate surfaces of such batteries become hardened. Instead of being transparent, the electrolyte has a slightly milky appearance.
- The sulfating process may be reversed if a severely discharged battery is recharged immediately.
- If battery is not recharged, plates will continue to harden, and ability to accept a charge will diminish. This results in reduction of battery performance.
CAUTION:
Risk of injury from battery acid.
- Prior to handling or servicing batteries, read, understand and observe the Warnings and Safety Measures for lead-acid batteries for lead-acid batteries → Safety Precautions !
- Wear protective eyewear and clothing → Lead-Acid Battery, Safety Precautions .
- On non-maintenance-free batteries, the sealing plugs must be installed tightly.
- Provide sufficient ventilation.
- If the magic eye has no color or is light yellow, the battery may not be tested or charged. Jump starting must not be used! There is a risk of explosion during testing, charging or jump starting. The battery must be replaced.
- DO NOT battery test batteries which are gassing. Otherwise there is a risk of explosion.
- Rapid-charging batteries → Battery, Quick Charging .
- Dispose of electrolyte (sulfuric acid/water mixture) properly! Waste electrolyte must only be disposed of in appropriate waste disposal sites. Refer to local regulations pertaining to electrolyte disposal.
- The following notes and procedures must be followed to ensure correct charging.
CAUTION:
Risk of severely discharged batteries freezing.
- Severely discharged batteries freeze at low temperatures, the housing can crack.
- Batteries that have frozen must no longer be used.
Prerequisite
- Battery temperature must be at least +10 C.
Procedure
Severely discharged (sulfated) batteries must be charged using a low charging current:
NOTE:
- The Midtronics Diagnostic Conductance Charging Station INC-940 automatically detects severely discharged batteries and carefully starts the charging procedure with a low charging current. The charge current is automatically adjusted to the battery charge state.
- In order to initiate charging procedure, battery voltage must be at least 0.6 V!
CAUTION:
Risk of damaging severely discharged batteries.
- Do not quick charge severely discharged batteries.
- Charge battery → Battery, Charging with Midtronics Diagnostic Conductance Charging Station INC-940 .
- The charging voltage may be a maximum of 14.4 V.
NOTE:
- If battery is replaced, follow disposal regulations → Lead-Acid Battery, Safety Precautions .