I used to leave my motorhome plugged in all the time and let the onboard charger keep the batteries charged. But I found myself having to replace the house batteries every couple of years as I think the onboard system was supplying too much charge to them. I keep my motorhome in indoor storage and I have a 15 amp outlet inside. I've found I can disconnect the house batteries with the switch up front and they keep their charge for several months. But the chassis batteries get a little draw from the engine computer and they will be dead in a couple of weeks. I had bought a battery maintainer for a 12 volt system and I attach it to the chassis batteries while the RV is in storage, but I think it's too small to keep up with both batteries as after a few days it starts giving an error signal. What I'd like to find is a decent battery maintainer that I can hook straight to the chassis batteries to keep both charged without having to power the onboard inverter at all. Anybody got any suggestions for one that will work to keep two 12 volt batteries charged?

They do make a dual battery maintainer.....I know this cause I have one that I never installed. I had been spoiled with getting batteries from my brother(Interstate battery franchise owner) so for 15 years I didn't worry about it. ( truth be told he always gave me the good used batteries including 8D and a half dozen 6 volt unless he had 4D's available.....I wasn't too picky!) Long story short, I just had to pay for the first time for both starting and chassis batteries....I didn't like it!! I always leave the MH plugged in at home but I am also thinking along your lines and finally trying out that maintainer. Sorry for the long post and rambling on...:)

Never tried to keep 2 batteries charged at the same time....my gasser has one 12V chassis battery... but "Battery Tender" brand makes some of the best trickle chargers/maintainers on the market, IMHO. You may want to check out their website to see if there are any products that will fit your need. FWIW, I installed one for my chassis battery to maintain it while plugged in to shore power or running the genset.Battery Tender

I'm looking at the Battery Tender and I see they have one that has four separate charging units. I think the problem I have with my current one (which is a Battery Tender Model) is it's a single 12 volt charger and I'm hooking it to one battery, but both batteries are connected to each other. So I'm wondering if with their four batter unit, can I hook one to each of the chassis batteries and will it work even with leaving the batteries hooked to each other? I'm trying to avoid having to disconnect batteries. I take fairly good care of my motorhome and I go to it at least once a month and make sure it gets started and driven around. I don't want to be messing with connecting and disconnecting batteries. I just want to unplug it an go.Not to mention I used a battery tender on my Harley Davidson and I got 9 years out of the original battery. So I want to use a battery tender on it.

I keep my RVs hooked up to a smart marine charger that is on a timer so it only comes on for a short while a day.bumpy

Battery Maintainer | Good Sam Community

Acampingwewillg
Explorer II
Apr 19, 2017
They do make a dual battery maintainer.....I know this cause I have one that I never installed. I had been spoiled with getting batteries from my brother(Interstate battery franchise owner) so for 15 years I didn't worry about it. ( truth be told he always gave me the good used batteries including 8D and a half dozen 6 volt unless he had 4D's available.....I wasn't too picky!) Long story short, I just had to pay for the first time for both starting and chassis batteries....I didn't like it!! I always leave the MH plugged in at home but I am also thinking along your lines and finally trying out that maintainer.

Sorry for the long post and rambling on...:)
2oldman
Explorer II
Apr 19, 2017
Disconnect them.
10forty2
Explorer
Apr 19, 2017
Never tried to keep 2 batteries charged at the same time....my gasser has one 12V chassis battery... but "Battery Tender" brand makes some of the best trickle chargers/maintainers on the market, IMHO. You may want to check out their website to see if there are any products that will fit your need. FWIW, I installed one for my chassis battery to maintain it while plugged in to shore power or running the genset.

Battery Tender
msmith1199
Explorer II
Apr 19, 2017
I'm looking at the Battery Tender and I see they have one that has four separate charging units. I think the problem I have with my current one (which is a Battery Tender Model) is it's a single 12 volt charger and I'm hooking it to one battery, but both batteries are connected to each other. So I'm wondering if with their four batter unit, can I hook one to each of the chassis batteries and will it work even with leaving the batteries hooked to each other? I'm trying to avoid having to disconnect batteries. I take fairly good care of my motorhome and I go to it at least once a month and make sure it gets started and driven around. I don't want to be messing with connecting and disconnecting batteries. I just want to unplug it an go.

Not to mention I used a battery tender on my Harley Davidson and I got 9 years out of the original battery. So I want to use a battery tender on it.
Bumpyroad
Explorer
Apr 19, 2017
I keep my RVs hooked up to a smart marine charger that is on a timer so it only comes on for a short while a day.
bumpy
bob213
Explorer
Apr 19, 2017
My Battery Minder Plus keeps both batteries charged in my diesel truck during winter storage.
midnightsadie
Explorer II
Apr 19, 2017
I have a cheapy from harbor frht hooked to two batteries keeps them charged all winter ,third year on this charger.
crasster
Explorer II
Apr 19, 2017
Go with a Battery Minder with desulphator. You'll love it.
Gjac
Explorer III
Apr 19, 2017
There are several ways to maintain batteries, but what I do is fully charge both house and chassis batteries then disconnect them. They set for 3 months over the winter that way. During the camping season I do the same until I plan on going camping, then will plug MH into my 50 amp plug and charge several days with my old Mangntec converter charger and the refer cools at the same time. The HF maintainer charger will charge the chassis battery. I also have a B&D 40 amp charger that can equalize and desufate. I equalize every 3 mos or so and desulfate maybe twice a year. Batteries will be 10 years old this year and I dry camp 95 persent of the time. I think leaving the charger on continuously eats away at the lead plates quicker, you just don't want to let them sit too long in a discharged state or they will begin to sulfate.
stevenicol
Explorer
Apr 19, 2017
I keep my two 6-volt AGM batteries charged and maintained with a battery tender. You can keep 2 12 volt batteries charged and maintained the same way; connect the batteries in tandem so that the battery's amp hours are added and the voltage stays 12 volts: a 12-volt charger will keep them "full."