How to Test Wet Cell Batteries

by C.L. Rease

Wet cell batteries contain dissimilar metals that rest in an electrolyte. The acidic electrolyte causes the metals to dissolve and release electrons. The release of electrons allows the battery to create electricity. Routinely testing the battery for correct voltage and electrolyte levels -- in non-sealed batteries -- ensures the battery will not fail when you need to start your vehicle. Taking proper safety precautions while testing the battery will keep you safe from the acid contained in the battery cells.

Non-maintenance Free Batteries Hydro Test

1

Remove the caps from the top of the wet cell battery.

2

Squeeze and hold the bulb located at the top of a temperature sensing hydrometer. Lower the pickup tube located at the bottom of the hydrometer into the first battery cell.

3

Release the bulb to draw electrolyte from the cell into the large tube of the hydrometer. Allow the electrolyte to stop fluctuating. Read the number printed on the internal float to determine the specific gravity of the fluid. Squeeze the bulb to release the fluid from the hydrometer. Measure each cell as described.

4

Compare the specific gravity of each cell. Replace the battery if one or more wet cells reads a specific gravity lower than the other cells. A lower specific gravity signifies the electrolyte in the cell is losing its ability to hold a charge.

Test Battery Amperage and Voltage

1

Charge the wet cell battery with a battery charger until the battery reaches a full charge. Disconnect the battery from the charger. Allow the battery to sit disconnected for 10 to 12 hours.

2

Connect a load tester to the positive and ground battery terminals. Read the load amperage rating printed or stamped on the battery. Set the amperage on the load tester to the number read on the battery. Turn on the load tester. Read the amperage displayed on the tester. A number displayed on a load tester at or near the recommended level signifies a good battery.

3

Recharge the battery with the battery charger. Disconnect the battery charger from the fully charged battery.

4

Hold the positive lead from a voltmeter on the positive terminal post and the negative lead on the ground terminal post of the charged battery. Read the number displayed on the voltmeter. The voltage of a good battery will be at or slightly higher than the stated voltage. For example, a 12-volt battery will have an actual voltage slightly higher than 12 volts.

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