Dear Dave,
I want to replace my two 6-volt house batteries with a single 12-volt deep cycle battery. Both batteries are dead at this point. The battery I’m looking at is an Interstate and I’m told it is 90-amp hours. My questions are: Will this be enough for a day’s travel using only the water pump until plugged in at night, and will the driving keep the battery charged? Thank you for your help on this. —David, 2016 Minnie Winnie 31K
Dear David,
The water pump in your Minnie Winnie is a Shurflo pump that takes a very small amount of 12-volt power and only when the pump is running. You suggest a day’s travel, so the pump would not be pulling any power while you are driving, just when you stop for a break and use the toilet or faucets, which would only be a very short time for the pump to run. So yes, the 90-amp hour Interstate would be sufficient, in my opinion, even if you did not get a charge from the alternator.
Since your rig is a Class C, it most likely is on the Ford E450 chassis and has a 120-amp alternator that would supply approximately 15 volts to charge the house battery. If you had two batteries, then the unit came with the convenience package as an option with two Group 24, 12-volt batteries.
On third set of batteries
Since you are wanting to replace two 6-volt batteries, these were not original and you are on your third set of batteries. The two 6-volt batteries were connected in series, meaning positive to negative, to give you 12 volts, but did not double the amp hours. So the 90-amp hour would have approximately the same power as your 6 volts when they were in good condition.
I believe your 90-amp hour Interstate is most likely a Group 27. Keep in mind you should only use 50%, which gives you 45 amp hours. If you want to do any type of dry camping, that one battery will not be sufficient to run the refrigerator, even on LP, and some interior lights. You have the space to go with two of these and would be much happier if you want to pull over in a rest stop overnight or other temporary dry camping.
However, your rig did come with a 4000-watt Cummins generator, so you could also fire that up to provide 120-volt power to the distribution center and ultimately to the converter, that will also charge the batteries.
You might also enjoy this from Dave
6-volt or 12-volt batteries for RVs—Which is better?
Dear Dave,
I keep reading about using two 6-volt batteries in series for RVs. Why? It seems like it would be simpler to have one 12-volt or two 12-volt batteries in parallel. Sorry, still a newbie trying to figure all this stuff out. —Richard, 2023 Geo Pro 19FDS
Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”
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