How to Check Your RV Battery

Checking your battery involves performing these two tests on a regular basis.

Instructions

Difficulty: Moderately challenging

Preparation

1. Access the battery you wish to check.
2. Make sure you are checking the 12-volt DC battery and not something connected to the 120-volt AC power supply. Run checks on all batteries in your vehicle and record the results.
3. Remove battery caps.

The Specific Gravity Test

4. Perform a specific gravity battery test by inserting the syringe from the temperature-adjusted hydrometer and extracting the electrolyte (battery acid).
5. Read the gravity level. Record the result.
6. Return the electrolyte to the battery.
7. Repeat this procedure for each battery cell.

The Open-Circuit Voltage Test

8. Perform an open-circuit voltage test only if the battery has not been charged within the past 24 hours.
9. Remove negative battery cable.
10. Read the voltage across the negative and positive posts with a voltmeter. Record the result.
11. Reconnect the battery cable.
12. Close the hood or compartment storing the battery.

Tips & Warnings

• The most common causes of premature battery failure are overcharging, sustained undercharging, sulfation and poor maintenance.
• Electrolyte (battery acid) is corrosive to metal, skin, cloth, and so on. If spilled on skin or squirted into eyes, flush with baking soda and water to neutralize the acid and get immediate medical attention.
• Batteries can give off explosive gases.
• Never perform a specific gravity test immediately after adding distilled water.
• If the specific gravity test on any two cells in one battery has more than a .50 differential, the battery is bad and should be replaced.
• With the specific gravity value test, the specific gravity level will read 1.265 if charged at 100 percent, 1.225 if charged at 75 percent, 1.190 if charged at 50 percent, 1.155 if charged at 25 percent and 1.120 if discharged.
• Running the engine or plugging it into a 110-volt power source will charge the battery.
• With the open-circuit voltage test, the voltage will read 12.6 or higher if the battery is charged 100 percent, 12.4 at 75 percent, 12.2 at 60 percent, 12.0 at 50 percent, 11.7 at 30 percent and 10.5 at zero.