Battery Testing 101

May 16, 2018 | RV Maintenance

How To Test A Battery To Industry Standards

Visually check battery for any signs of bulging or swelling. Check case for damage. Check electrolyte level and, if necessary, fill to one half inch above plates with distilled water.

Check state of charge in battery. If battery is below 12.60 volts, battery must be recharged before it can be tested with a load tester or digital tester. 12.60 volts is considered a fully charged battery. Charging times vary depending on capacity of charger and Amp hour of battery. For example, fully charging a completely discharged automotive battery with a 5-amp charger may take 12-20 hours, while using a 10-amp charger may take 6-10 hours.

After charging, remove surface charge by applying the batteries CCA rating for 10 – 15 seconds (wait 15 minutes before applying this load, hydrogen gas may be present, and is highly combustible.) Wait 15 minutes before applying the two additional loads required for determining if the battery is good or not.

Test with a carbon pile load tester; test battery at half the CCA rating for 15 seconds two times. If voltage drops below 9.6 volts while load testing, then the battery has failed the load test. If battery is not rated in CCA, load test at 2 times the Amp hour.

Specific Gravity Test

This test is performed with a hydrometer, which is the most accurate hand held tool for determining the state of charge of a lead acid battery.

Hold hydrometer vertically so that the float is free and does not touch the inner walls of the battery.

Draw electrolyte into the hydrometer, making sure that the hydrometer is full.

Check each individual battery cell. If the specific gravity is not reading 1.260 in each cell, you must recharge battery. If each cell reads 1.260 or higher, the battery is good for testing.

What to Look for While Testing

Battery is discharged:
A battery is deemed discharged and not suitable for testing if the battery is below 12.60 volts (maintenance free) or if you are getting a specific gravity reading below 1.260 per cell.

Solution Charge battery to achieve 12.60 Volts, and a specific gravity reading of 1.260. You can load test the battery when the battery is 100% charged.

Battery has one dry cell:
This is an indication of two things; either the battery has a shorted cell, or there is a puncture somewhere on the casing, usually caused by a pebble getting into the battery tray during use, or the installers not cleaning out the battery tray before installation. The pebble will sit there while the application vibrates, and it will create a small hole.


Pour water into the dry cell, wait a couple seconds, if the battery starts leaking then there was user error, and no warranty should be issued. Put a load on the battery using a carbon pile load tester if the cell does not leak. You should see bubbling in the cell, which indicates a short cell, free replacement warranty should be issued in this case.

All cells are dry in the battery:
This is an indication of overcharging, or neglect to water the battery. No warranty should be issued.

Battery is overcharged:
There are a few distinctive traits of overcharging. In flooded batteries, all the cells will be dry, or the electrolyte will be extremely muddy, or black looking. In AGM batteries the distinctive trait is case bulging, labels melting off the battery, or the plastic around the posts are melting.

Frozen Batteries:
The batteries cells or one cell will be frozen, or the case will be cracked due to thermal expansion. No warranty should be issued.


(If the battery has not cracked) Bring the battery inside, and let it thaw at room temperature. Once the battery has thawed, and hopefully hasn’t cracked, place on charge. (Never attempt to charge a frozen battery).

Battery Cells have varying Specific Gravity readings:
Check each individual battery cell. Specific gravity should not vary more than .050 or “50” points between cells. If a cell varies more than .050 points, charge again, if this difference remains it could be an indication the cell with lower specific gravity reading has failed or could fail soon.


For assistance or to learn more, we invite you to contact our team of RV professionals. We hope to hear from you soon!

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