Quick Answer
Conduct a cell-by-cell health check on batteries by using a hydrometer or multimeter to measure specific gravity and voltage levels, then comparing these values to the manufacturer's specifications and industry standards.
Measuring Specific Gravity
To measure specific gravity, use a good-quality battery hydrometer with a high accuracy rating, such as a 0.0001 specific gravity resolution. Take multiple readings from each cell, ideally three to five, and record the average value. Compare this value to the manufacturer’s specified range, usually between 1.265 and 1.310 for lead-acid batteries, to determine the cell’s health.
Interpreting Voltage Readings
Use a multimeter to measure the voltage of each cell, ideally with a 10% margin of error. Compare these values to the manufacturer’s specified range, usually between 2.2 and 2.5 volts for a fully charged deep cycle battery. A voltage difference of more than 0.1 volts between cells may indicate a cell imbalance, which can lead to premature aging and reduced overall battery performance.
Identifying and Repairing Imbalances
If you identify a cell imbalance, separate the battery into individual cells for further evaluation. Check for signs of physical damage, such as cracks or corrosion, and clean the terminals and connectors if necessary. If a cell is significantly undercharged or overcharged, recharge it slowly using a battery charger or trickle charger to bring it back to the recommended specific gravity and voltage levels.
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