Battery Fault Diagnosis

Fault	Cause	Remedy
Electrolyte level too low.	Overcharging, evaporation (especially in summer).	Top up with distilled water to the specified level (with battery charged).
Acid escapes from the vent cap.	Charging voltage too high.

*' Electrolyte level too high.

• Check voltage regulator, replace if necessary.
• Remove excess acid with an acid syringe.

Acid density too low. Acid density in one cell significantly lower than in the other cells.

Acid density in two adjacent cells significantly lower than in the other cells.

Battery discharged.

Alternator faulty.

Short circuit in wiring system.

*' Acid diluted due to maintenance error.

• Short circuit in one cell. Replace battery.
• Partition wall leaking, creating a conductive connection between the cells, which discharges the cells.

Replace battery.

Charge battery.

Check alternator, repair or replace if necessary.

Check electrical system.

Carry out acid balancing.

Acid density too high. Acid was topped up.

• Carry out acid balancing.

Output too low, voltage drops sharply. Battery discharged.

Charging voltage too low.

Terminal clamps loose or oxidized.

Ground connections battery-engine-body are poor.

Excessive self-discharge of battery due to contamination of the battery acid.

Battery possibly sulfated (grey-white coating on positive and negative plates).

Battery worn out, active material of plates has failed.

• Recharge battery.
• Check voltage regulator, replace if necessary.
• Clean terminal clamps and lightly grease them with acid-protection grease, especially the undersides; tighten mounting screws.
• Check ground connection, if necessary establish metallic connections or tighten screw connections.
• Replace battery.
• Charge battery with low current so that the coating slowly breaks down. If output is still too low after repeated charging and discharging, replace battery.
• Replace battery.

Battery insufficiently charged. Fault in alternator, voltage regulator or wiring connections.

Drive belt loose, tensioner defective.

Too many consumers connected.

• Check alternator and voltage regulator, repair or replace as necessary; secure wiring properly.
• Tension or replace drive belt, check tensioner.
• Fit a larger battery; if necessary, also use a larger alternator.

Permanent overcharging. Fault in voltage regulator, possibly also in alternator.

• Replace voltage regulator.

Check alternator.

*) The notes marked *> do not apply to the standard low-maintenance battery.