Ask Dave: When RV is plugged in to shore power, why isn’t house battery charging?

Dear Dave,
When my RV is plugged in to shore power it doesn’t charge the battery. Is there a fuse inside the charger? When I turn on power I hear the cooling fan turn on briefly. There’s power going in but nothing out. —Claire, 2017 Winnebago Minnie Winnie 25B

Dear Claire,
Your Winnebago Class C Minnie Winnie is equipped with a WFCO all-in-one distribution center that is located under the bed pedestal, according to the Winnebago 3-D parts documentation.

Distribution center with circuit breakers

This is a 30-amp distribution center that has circuit breakers for the 120-volt operations and 12-volt fuses for the systems that run off the house batteries. It also has a built-in 55-amp converter, which is the charging system for the house batteries.

Your Minnie Winnie also came standard with two 12-volt deep cycle batteries that are in the outside compartment on the passenger side of the rig next to the entrance door. The original batteries were NAPA group 24, which may not be there now as most house batteries will not be properly charged to prevent sulfation. The WFCO converter will recognize a low battery and initiate a 13.6-volt charge until the batteries register 12.6 volts and then will drop to a maintenance charge of 13.2 volts.

As batteries are drained of power, sulfation begins to coat the plates inside the battery. A multistage charge starting with a high voltage “bulk” charge breaks up the sulfation and then goes into a equalizing and float charge. You can test what your converter is doing by using a multimeter on the 12-volt DC setting. I would suggest starting with the unit unplugged and test the state of charge of your current batteries. Fully charged they should be reading 12.9-volts. Anything lower would indicate they are probably sulfated. Then plug the shoreline cord into a 30-amp source and it should be either 13.6 volts or 13.2 volts. If the voltage does not change from what the batteries read, then it verifies the converter is not working.

Check the circuit breaker

In this case, I would first check the circuit breaker on the distribution panel. You should see a dedicated circuit breaker for the converter. If that is in the on position, you need to verify the circuit breaker is good and the converter is getting 120-volt power that it will “convert” to 12-volt power for the battery. This converter is located on the bottom portion of the unit. From there, I would check the connection of the converter to the batteries. If all that checks out, the converter is bad and you should be able to replace just that part.

Note: Be very careful working around 120-volt power. Most of these tests should only be performed by a qualified technician. Testing the 12-volt power going to the battery with a multimeter is a test the average RVer can perform safely.

If your converter is providing 13.2 – 13.6 volts and your batteries are not holding a charge, then they are the problem, not the converter.

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Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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