Testing your RV Batteries, the correct way.

With the changing of the seasons here in central PA and a wintry mix forecast in the weather,come some mandatory maintenance tips for your RV. One of which is checking the charge on your batteries. I think that many times we take this for granted, but a battery that lies dormant for extend periods of time will lose it’s charge. There is nothing more frustrating than a dead battery. The sad part is that is very easy to do.

Testing the battery state of charge is not difficult to do. There are basically three ways to test the condition of your RV batteries. Here is a great explanation from blog.rv.net:

  • The three ways are:1) You can use the monitor panel in the RV.

    2) You can measure the voltage with a digital voltmeter.

    3) You can test the specific gravity with a hydrometer.

Lerch RV, the place for your RV Parts.

RV Monitor Panel

The least accurate of the three testing methods is the RV monitor panel, but if this is your only means for checking the battery(s) it will give you a general idea of the condition. When you check the condition of your battery using the monitor panel make sure the RV is not plugged in to shore power, if it is you will get a false fully charged reading. To get a more accurate reading of the battery’s condition check the monitor panel when the RV is not plugged in and turn a couple of overhead lights on to place a small load on the battery.

Voltage Meter for RV Battery testing.
Measuring voltage with a voltmeter has its advantages. If you have sealed batteries your only choice is to use a voltmeter, and measuring voltage can give you a quick picture of the batteries depth of discharge, so you know when they need to be recharged. To measure the voltage you need a good digital voltmeter. Set the meter on DC voltage and connect the red lead to the positive terminal and the black lead to the negative terminal. A 12-volt battery that is charged should read 12.5 to 12.7 volts. Readings less than 12.5 indicate the battery state of charge is below 80% and the battery needs to be charged. A 6-volt battery that is charged should read 6.25 to 6.37 volts. Readings below 6.25 indicate the battery state of charge is below 80% and the battery needs to be charged.

The preferred method of RV Battery Testing.

The Hydrometer is the best method of testing your RV Battery

The preferred method for testing the battery’s state of charge is to check the specific gravity reading of each cell. This method is a little more involved, but it’s worth the time and minimal cost. You can purchase a hydrometer at an auto parts store for about ten dollars. The electrolyte in the battery cells is a solution of acid and water so you need to wear safety glasses and gloves and avoid any contact with your skin. The first step is to remove the vent caps and check the electrolyte levels. There has to be enough in the cells for the hydrometer to pick up a sample. If you have to add any water prior to testing you will have to charge the battery and let it sit for 12 hours before testing the condition of the battery.
Next, fill and drain the hydrometer at least twice in each cell before taking a sample. Take the reading and record it and drain the electrolyte back into the cell you are testing. Test all of the cells and replace the vent caps when you are finished. Specific gravity readings for a charged battery should read between 1.235 and 1.277. Specific gravity readings below 1.235 indicate the battery state of charge is less than 80% and the battery needs to be charged. If there is a .050 or more difference in the specific gravity reading between the highest and lowest cell, you have a weak or dead cell in the battery.

If that was a little difficult to understand, take a look at the video below. It is a great explanation of how the hydrometer works:

If you put your RV in long-term storage it’s a good idea to remove the batteries and put them in storage too. This is quite simple to do. When you remove a battery always remember to remove the negative terminal first and then the positive terminal. Knowing the battery state of charge and re-charging a discharged battery in a timely manner will extend the life of the battery.

Caution: RV batteries can be dangerous to work around. If you are not familiar with batteries or if you do not feel comfortable working around batteries you can always bring your RV in to us and have us take a look.