Monday, June 5, 2023


Ask Dave: I installed new batteries and now they need more water. Why?

Dear Dave,
I took out the two 12-volt batteries and added four 6-volt golf cart batteries—two in the original spot under the step in series and two in the compartment right behind the step. Next, I wired them in parallel and then connected them to the inverter. I have solar attached to the two in the compartment. The new batteries seem to need more water. Should the solar be connected to the under-step batteries for a more even charge? —Alan, 2018 Winnebago 29VE

Dear Alan,
From what I can find on the Winnebago spec site, the 29VE you referred to is a Class A Vista with a full-body slide on the driver’s side. You have the two 6-volt batteries you installed under the steps in the original configuration and the other two in the compartment directly beside the entrance door.

Originally the unit came with two group 24 12-volt batteries in the stepwell and a chassis or start battery.

It also has a 45-amp converter/charger that will provide a charge to the battery bank at 13.8 volts when the battery bank needs to be charged, then drops to a 13.2-volt maintenance charge. I believe it is a Magnatek product. According to their tech support, the converter will provide a 13.8-volt charge for eight hours. That’s how Winnebago wanted it spec’d to try and disulfate the batteries. This is mounted under the dinette.

The inverter is simply a 1000-watt unit that takes 12-volt power from the battery bank and provides 120-volt power to designated outlets. It is located in the second compartment back from the entrance door and does not act as a converter/charger, so it should have no effect on the battery bank other than drawing power when boondocking.

Check the battery-connecting gauge cable

Check the gauge cable you used to connect the two batteries in the compartment as well as the two in the step. You might need to go with a heavier cable. The Thor we just worked on had the converter under the bed and almost 20 feet of cable. It was a 6-gauge and heavy enough to handle the higher output of the lithium charger. I would suspect yours is 8-gauge, but I cannot find it on the prints—just a part number for the wire assembly.

Check connections between solar charger and converter

When connecting batteries to a charging source, whether it’s the converter or a solar charger, it’s always best to connect one lead to a battery and the other to an opposite bank. It would be best to check your connections between the solar charger and the converter. Also, the two batteries in the stepwell are in a vented compartment and the other two are in a sealed compartment. It could be they are running hotter or colder. Lead-acid batteries will gas, especially 6-volt ones, and the compartment needs to be vented. If you don’t want to cut a large hole in the compartment, I would suggest getting a vent lid and hose like some trailers use. Then just cut a small hole for the vent tube and you will keep moisture out.

Cross-connect and meter batteries

So, back to your question about switching the solar cables to the other batteries. Keep in mind there is the converter that will also affect what you are getting for a charge to the batteries. I think it’s best to cross-connect, as stated earlier, but also to put a meter on the batteries independently to see what they are getting for a charge from the converter. They should all be 13.8 volts during the 8 hours of charge and 13.2 volts from the converter.

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.

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Dave Solberg
Dave Solberg
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. He has been in the RV Industry since 1983 and conducts over 15 seminars at RV shows throughout the country.


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Thomas D
1 year ago

I learned last year that if any cell is bad, and i mean ANY, that the charger, converter whatever you care to call it will boil the water out of the batterys. It will attempt to charge battery and can’t. Check individual cell with hydrometer to see if they are equal. Even new doesn’t mean good.

1 year ago

Four 6-volt batteries wired in parallel equals 6 volts, no?

1 year ago
Reply to  wayne

I also had the same thought until I reread the first paragraph. He states that the two 6 volt batteries in the battery space are wired in series. The other two batteries are wired in parallel . I would need to see the wiring before making and judgement.

Mike Schwab
1 year ago
Reply to  wayne

The two batteries in each compartment are in series for 12 volts, then parallel between the two compartments for higher capacity.

1 year ago

Dave, didn’t see an answer about “I installed new batteries and now they need more water. Why?” Seems like Alan had several questions for you! How about an answer about the water issue!

1 year ago

Caught that too did you!

1 year ago

Another reason I am so glad I switched to lithium. Flooded lead, never again.

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