Visually checking the battery.
Checking the electrolyte level in cells on batteries with caps. Adding water if the electrolyte level is low.

Cleaning off corrosion around the battery and battery terminals.

Figure 2-5.- Electrolyte mixing chart.

Checking the condition of the battery by testing the state of charge.

VISUAL INSPECTION OF THE BATTERY.- Battery maintenance should always begin with a thorough visual inspection. Look for signs of corrosion on or around the battery, signs of leakage, a cracked case or top, missing caps, and loose or missing hold-down clamps.

CHECKING ELECTROLYTE LEVEL AND ADDING WATER.- On vent cap batteries, the electrolyte level can be checked by removing the caps. Some batteries have a fill ring which indicates the electrolyte level. The electrolyte should be even with the fill ring. If there is no fill ring, the electrolyte should be high enough to cover the tops of the plates. Some batteries have an electrolyte-level indicator (Delco Eye). This gives a color code visual indication of the electrolyte level, with black indicating that the level is okay and white meaning a low level.

If the electrolyte level in the battery is low, fill the cells to the correct level with DISTILLED WATER (purified water). Distilled water should be used because it does not contain the impurities found in tap water. Tap water contains many chemicals that reduce battery life. The chemicals contaminate the electrolyte and collect in the bottom of the battery case. If enough contaminates collect in the bottom of the case, the cell plates SHORT OUT, ruining the battery.

If water must be added at frequent intervals, the charging system may be overcharging the battery. A faulty charging system can force excessive current into the battery. Battery gassing can then remove water from the battery.

Maintenance-free batteries do NOT need periodic electrolyte service under normal conditions. It is designed to operate for long periods without loss of electrolyte.