Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club. Today he discusses charging an RV’s house batteries from a house outlet.
Happy Holidays, Dave.
I have a 2019 Gulfstream BT Cruiser 5230B. My two 12-volt house batteries will charge with an onboard Onan 4000 generator or with my 6.8 V-10 engine running. However, the batteries don’t charge up when my MH is plugged into a standard house 110 outlet. Inverters/converters are off, as with any/all appliances. Is my outlet insufficient to keep these batteries charged? Thanks for the assist. —Karl
Happy Holidays to you, too, Karl.
The short answer is there may not be enough power available from your residential source to run everything in the rig and provide a charge to the battery from the converter.
First, let’s look at the residential source you are plugging into. If it’s a typical 20-amp outlet in the garage or side of the house, it is probably not a dedicated outlet. Ir’a probably rather “ganged” to other outlets in the garage that might have power-drawing components plugged in such as a freezer, refrigerator, air compressor, etc. So, you may not be getting a full 20 amps available to the rig and the distribution center.
The size of electical cord is important
Another consideration is the size of electrical cord. The cord in this photo is a “heavy duty” cord from a hardware store. However, it is only rated at 10 amps, which is not sized for plugging in an RV but, unfortunately, happens quite often.
When you plug into a power source, the shoreline cord goes to the distribution center which has circuit breakers for 120-volt appliances inside the rig as well as the converter, which is your battery charger. If you are running the refrigerator or any other appliance, it will draw amps as shown in the chart below.
Although the refrigerator doesn’t draw a lot of amp power, if you have anything else on in the rig, there will not be sufficient power available to the converter to charge the batteries.
Test charge coming in at the batteries
One test you can conduct is to plug the unit in to the 120-volt source and use a multimeter to test the charge coming in at the batteries. Set it to the 12-volt DC setting and place the red probe on a positive post and the black on negative. If your batteries are lower than 12.6 volts, the converter should be applying a 13.6 volt charge or higher if it’s a multi-stage or desulfation charger. Then it should go to a 13.2 volt maintenance charge.
Here is how the typical converter operates, when the batteries are lower than 12.6 volts. The charger applies a 13.6-volt charge until the batteries get to 12.6 volts. Then the charger goes into a maintenance state of 13.2 volts. A typical battery fully charged at 12.6 volts will not accept a charge lower than 13.2 volts, so it stays there as a maintenance charge. If your multi-meter shows 13.2 volts, then I would shut off the converter at the distribution center and disconnect the battery cables and test the battery as it sits. If it is lower than 12.6 volts, there is a problem.
Read more from Dave here.
HAVE A QUESTION FOR DAVE?
We have started a new forum link for Ask Dave. Please be as brief as possible. Attach a photo or two if it might help Dave with his response. Click to visit Dave’s forum. Or send your inquiries to him using the form below.