Battery maintenance is an important part of RV travel and caring for the batteries is paramount. Here’s the story of how I take care of mine. [Hoisted on my own petard with that statement…I didn’t do any maintenance for over a year, and that almost ruined my set of 6 volt deep cycle batteries].
When I bought this ’02 Winnebago in February of 2016, I could see from the battery level indicator inside the RV that the house batteries were bad. Showing only 10.2 volts whenever I visited the RV before I picked it up. Any battery below 10.5 volts is dead and if allow to go below that repeatedly for extended periods is bad. And it should hold a charge for more than the 12 hours that I’d noticed it. It sank down into the 10 volt region far too quickly.
I told that sales guy about it and he insisted that they were great, the best batteries ever. I called him a lair to his face and eventually got a $1,000 discount on the sales price and that amount included new batteries…but I’d need to buy and install them myself.
Since I was sensitized to batteries and battery maintenance having been an RV’er for 14 years by this time, of course I checked the battery compartment before I drove it off the lot, and it seemed to have a couple pounds of that white corrosion powder in the bottom of the battery trays but they had cleaned the terminals so there was little on them. It didn’t take long to show back up there though, and mainly on the 2 wet cell 12 volt batteries that the dealer had swapped into my new-2-me RV before I bought it. Those were obviously bad batteries they’d pulled from other RVs as they should have been 6 volt. I definitely noticed that so I used that as leverage getting the $1,000 discount.
I bought and drove the Winnie home and then, I limped along for 11 months with those bad batteries. Heh. Got another year out of them almost. I don’t boondock much so as long as the alternator and then the converter when plugged into shore power kept them halfway charged up, I was okay with that. Really wasn’t that hard dealing with them as long as I didn’t leave the RV unplugged for more than 12 hours, so since I’m a full timer it would work fine for me. But eventually I felt it was time to replace them so I got a couple of 6 volt golf cart batteries from Costco for $89 each. From an Oregon store so I saved on taxes.
They won’t change them for you so you have to make arrangements for that. In my case I drove the RV to their parking lot, parked in a nearly empty area nearby their automotive shop and undid all the cables to those two batteries, covering the terminals with rags to prevent shorts to chassis ground as I left the Chassis batteries connected. Then I went in and bought the new ones, and the guy used a cart to carry them out to my RV, where we swapped. He was nice enough to lift the old ones out and put the new ones in, than took the old ones into his shop for the core value. And than I reconnected the battery cables but this time I was putting in 2X 6 volt batteries in place of the 2X 12 volt I’d removed. Than I went in and got my core refund. So not the simplest of procedures but pretty easy really.
Here’s a picture of the battery compartment. Note that the water heater is behind the same door.
And here’s some pictures of what the battery trays look like now…I never got many pictures of the nasty condition they were in originally, even though I had/have worked on them several times. Those smaller yellow, blue, and black wires are attach to the Trik-L-Start battery maintainer I bought a few days after buying the RV.
When I got back to the RV park I was staying at the day I bought the new 6 volt batteries, I removed all of the batteries…the 2 new 6 volt, and the 2 older 12 volt. I made up a bucket of baking soda water and I have my large acid brush with which I scrubbed the hell out of the older batteries and the battery trays. Rinsing them as I finished the scrub. Repeatedly flooded the trays clean with water. Gave them a really good washing. The way my RV site was situated, the neutralized acids didn’t pose a problem to the grass, cement slab, or drainage system. I was pretty careful about that just in case, made sure the acids were properly neutralized.
After they were all dry, scraped out the rusty flaked paint (wasn’t too much of that) then I lubed the tray bearings so the trays would operate a little bit easier when pulling them out. Used heavy duty lithium lube for that. All the dust you see now is the result of driving for thousands of miles without cleaning them.
After all that cleaning was done back in 2017, I used my drill with brass rotary brush and cleaned all the battery terminals. I’d used baking soda & water solution on them too. I was lucky that there wasn’t much corrosion…in the case of the cables, that green stuff…growing too far into the copper cables near the terminals. So I felt comfortable just cleaning them instead of tossing them and buying new.
With all that done in 2017, I happily drove around the country as a full timer for almost another year when it became obvious that it was time to pull some more maintenance on the batteries. They weren’t too bad but I felt it was time to add some mineral oil to the cells of the 6 volt batteries.
I opened the cells of the 6V batteries and using a graduated plastic turkey baster, removed 2 oz of electrolyte from each cell, and to neutralize it, squirted it into a bucket of baking soda and water I’d used to clean things with. Then I squirted 2 oz of 3-in-1 oil (which is mineral oil) into each cell. The 12 volt batteries are ‘sealed’ and ‘no maintenance’ types so they didn’t get the oil treatment. I had waited two years after purchasing the batteries mainly to get a feel for how much corrosion I was typically get. Not much, but some.
For those that don’t know, using mineral oil to float on the surface of the electrolyte in lead-acid battery cells is a tried and true method to prevent or reduce battery terminal corrosion. The method is over 100 years old. Even Edison used it and recommended that battery manufacturers of the time use it in new batteries. Of course they didn’t as that would make the batteries last a bit longer plus it cost them a few pennies. Well, the method and reasons for using it haven’t change over all those years and since I’m kinda lazy, spending a few bucks and time to add the oil so I won’t have to work at maintaining the batteries too often is to me a no brainer. So in it went. I would have added it to the 12 volt batteries if I could have, but after 3 years now and they aren’t corroding so I’m good with that.
What happens in the typical battery is you get an occasional bubble form on the plates as a chemical reaction that releases and floats to the surface of the electrolyte where it bursts. That burst is energetic, especially when ambient temperature is high or if the charger overcharges. That burst casts acid into the air inside the battery. And you’ll note that a standard lead acid battery has small holes in each of the cell caps. So if atmospheric conditions are right, that acid laden air will escape the battery and rush right to the nearest metal. And start corroding it. Over time it builds up enough that it starts corroding the more distant metals like the hold down bolts and the tray. When you add the oil, what it does is simply make that bubble less energetic when it bursts, or prevents it from reaching the surface. So the acid tends to remain in the solution rather than floating around in the air. Simple. However, there will still be some bubbles that reach the surface and burst and if conditions are right, you may lose some water from the cell, which just means you still have to do maintenance on the batteries…like add water, just not as often.
And here’s a view of the batteries today, 28 months after adding the oil. Note how corrosion free the terminals are? That’s what you can expect with the oil AS LONG AS your converter is a multistage charger. And is working properly. Even with the oil, if your charger boils the battery, you’re eventually going to have a bad day. But I had an old fashioned charger in my ’94 Bounder and that converter/charger did tend to over charge the batteries but with the oil, even then I’d have very little corrosion. So little that I once waited too long to add water and found the plates exposed more than an inch. But wait…the oil was coating the plates! And they weren’t buckled. So I just added water, and a year later, they were still working great. That’s how good the oil is. Saving you money all over the place.
These are pictures I took today, May 19, 2020 and you can’t see any corrosion. I also regularly wash them off with the hose, but didn’t bother today. Nothing else needs to be done except to check the water level in the 6 volt batteries occasionally.
Here’s the 2X 12 volt batteries (chassis batteries) in their own tray below the house batteries. As you can see they are not serviceable as they have no caps. I did try to pry up on those covers over the cells but they wouldn’t budge. Anyway, you can see there’s no corrosion anyway. 
So my point is, if you’re sick of having to mess with your batteries every 6 months or so, adding water, cleaning off the corrosion, buying extras like anti-corrosion pads or sprays, replacing corroded out cables, forget all that and just add mineral oil to each battery cell. You’ll be happy you did. Clean up all the old corrosion first though.
Finally, remember that adding the oil is NOT some new wave woo woo method. It’s over 100 years old, recommended by Edison himself and it works. It’s also not perfect, you still have to check your battery’s water levels occasionally. But I’ve only needed to add water once in 28 months. [Edit: Mistake on my part to wait so long…see below]. Your choice to do without the oil of course.
Update: June 2020
Arrived at the Clark County RV Park in John Day Oregon yesterday, June 2nd. Paid for 4 nights and plugged into the 50 amp outlet, but my Progressive wouldn’t click on. Normally I can hear it operate a few seconds after I plug in. This time, no clunk noise as the main relay closes after a time so a quick check and I see that line 2 is dead. Crap. Grabbed a 30 amp to 50 amp dogleg and I’m in business, only with 30 amp instead. An hour later, the groundskeeper comes by and tells me that most of the row is out and will be all night. Next day, the workers get here and shut down the row while they do some serious digging with big ass machines roaring while they water drill and vacuum up the dirt mud and water from a 4 feet deep hole trying to un-bury the big AC cables. So I have no shore power.
Now that I’m just sitting waiting, I occasionally check the battery voltage ‘cus there’s nothing else to do and after an hour or two, I checked and damn the house batteries have dropped to 10.6 volts. A 10.5 battery is totally dead. Continuing to discharge it below that will likely damage them. That’s not right. It should last for a few hours, not just one or so. So I quickly turned off the refer, the entertainment inverter, and the voltage jumped up to 10.8. So that will give me some time. Quickly grab some tools and head out and open the battery compartment and pull out the tray for the house batteries. Disconnect the ground cable from the 6 volt battery set so I can asses the damage.
Well, didn’t take long to discover that both 6 volt batteries were out of water. Water level was below the top of the plates. Crap. Okay, well, at least I had mineral oil in there and perhaps that protected the plates a little. But really, it was my massive mistake putting off checking them once a year like I was suppose to. I did check them near the end of the first year after I’d added mineral oil, serviced them by adding water like you’re suppose to but that was like 18 months ago. I waited too long. I’m a big Dummy.
I grabbed the nearly one gallon of distilled water I had and quickly added it, while also adding some more mineral oil. Not sure that was needed but I couldn’t tell either. Only put in around 0.67 oz of the two ounces per cell it calls for with a new battery so pretty sure that’s not too much. But I don’t know either, I’ll just use them until dead, and then update this report.
After adding the water and oil, the voltage jumped back up to 5.84 and 5.86 volts very quickly so that was pretty darn good I thought. Hinted that the batteries weren’t ruined like one would expect if one hadn’t used the oil. A good sign I’m thinking.
There still wasn’t any corrosion on anything in the battery compartment even after stressing them by letting them lose too much water. That’s what lulled me into a period of complacency. I’d look in there, notice how there was no corrosion, sigh about the work adding water, and then find something else to do. Part of the problem was the difficulty in seeing how much water they have.
And here’s a couple three pictures after cleaning. You can see that I have now turned the top two 6 volt batteries 90 degrees so going forward it’ll be much easier to check the water level. The way they were in the tray before made it a real pain because it was very difficult to disconnect the two big +/- cables just to pull out the tray as there’s hardly any room to get your hands or tools in there. One thing I’ve learned is I get more room if I disconnect the cabinet door’s air spring…doing that allows the door to be lashed up out of the way a few inches more. Turning the batteries also now allows the cables to be connected to the rear of each battery. This allows much more slack so the tray can be pulled way out, so now I can get to the fill holes without having to use a mirror & flashlight, a squeeze bulb, and guess work when adding water. Wish I’d put them in right originally when I bought them but I didn’t know and I put them in the way the old ones were in there. Which it turns out was incorrect due to them being 12 volt batteries instead of the 6 volt they were suppose to be. They’re suppose to be 6 volt deep cycle for longevity. But occasionally you see or read about RV’ers installing 12 volt starting batteries. Those can’t really take the deep cycling that a golf cart battery can take over the long haul.
You might notice that they seem to have a slight bulge. They were that way when I bought them so at this point it doesn’t bother me, but I’ll keep my eyes on it for sure…just in case.
And here’s the two 12 volt batteries after I cleaned all the dirt off. Still no corrosion on these. These are sealed no maintenance batteries so I haven’t added any oil but those sealed type batteries often never show corrosion until they’re almost dead or completely worn out. They seem to be a very well made battery by Delco. I’ve had them for 4 full years now and I don’t know how old they were when I got the RV but I have a hunch they were brand new in 2016. [Edit: Found the date sticker on the rear one of these 12 volt batteries. They were manufactured 8/19/15. So only a few months old when they went into my rig near 2/5/16.] They have either physical damage or some kind of crud on the sides of the batteries so I think they were pulled from a damaged or ruined RV and moved over to mine since I’d just bought it and dealers often swap parts like batteries around when someone buys. And I ended up getting them in my new to me consignment lot purchased RV, along with two House batteries in poor condition.
Based on the amount of corrosion powder in the bottom of the trays, I’d guess the batteries they pulled out were all in very bad condition. That sort of thing happens all the time on dealer’s lots.
This time, after cleaning all the dust and dirt out of the trays, I sprayed them with a lubricant and I hope that helps protect them from rusting any more…there’s not much now as it is though. I know it’ll capture dust too but for now the trays and batteries look pretty good. And the heavy duty rollers for the trays work really well now too.
So that’s the story. I screwed up and didn’t check on the batteries often enough and almost ruined my 2 house 6 volt batteries. Or perhaps I did ruin them…only a bit of time will tell me for sure.
Update: End of August 2020
It’s been fairly hot where I’m staying in Milton-Freewater Oregon and I wanted to check the house batteries since I damaged them early this year by waiting too long between maintenance sessions.
It’s been two months since I added water and I wanted to check how they are doing. I haven’t done any boondocking so I haven’t checked for how long they’d last in that situation but the voltage has been steady at 13.4 volts for the last two months. Anyway, I checked the two 6 volt house batteries and the water was down a bit. Took ~1/2 gallon, slightly less than that actually, of distilled water to bring them back up to full. I expect most of that loss was due to the heat wave. I’ll check again in another 2 months. BTW, still no corrosion on either set of batteries so the oil is doing it’s job.
Jim somebody (previous owner) installed 3 house batteries in the Journey I have. I replaced all 3 two years ago with 12 v, not much aware of 6 v. Glad you mentioned the water evaporation I have to add water about every 3 months and have a lot of corrosion. i’ll try the mineral oil.
Typically, 6 volt deep cycle are used for the house and there’s a good reason for that…because unlike a 12 volt starting battery, house batteries often can be discharged many times to 10.5 volts…the zero % level for a lead acid battery. They can do that because they’re made with thicker and larger plates inside, wider spacing between plates, and taller. Deep discharge repeatedly doesn’t automatically ruin deep cycle batteries which is why they’re used in RVs for the house. (Be advised that within the last 8 years or so, retailers have been labeling their 12 volt starting batteries as deep cycle…this is a lie if they also mention CCA’s and if the case size hasn’t grown).
In your case, even with adding the oil, better check them every 6 months because they’re like the wrong tool for the job. But you do have 3 of them which reduces the work each individual battery does, so if you add the oil, perform regular maintenance, and are careful about how much boondocking you do, you should be able to get several years from them. I’d say 5-7. Good luck!
We have 3 12-volt Walmart deep cycle House batteries in our ’04 Journey. I’m planning to replace them with 4 6-volt golf cart batteries from Costco. I believe they will just fit.
I appreciate your travel and maint/repair posts very much. Thanks!
I don’t believe Walmart sells a TRUE deep discharge 12 volt battery as the batteries I’ve seen in their display racks simply aren’t big enough. To be a true deep cycle they would be much bigger…too big for the average battery compartment in an RV, and they wouldn’t also list the CCA’s. What they did was go to congress, pay some of them off, and boom, they’re allowed to lie about it. Just look at how big two 6 volt deep cycle batteries are…any true 12 volt deep cycle would need to be that big. They do make them, I helped an RV’er lift two of them into his battery trays last year. Damn they were heavy. And just slightly smaller than two 6 volt batteries made together in the same case. Because that’s what they are.
Good news you’re planning on getting the 6 volt batteries. Those will be TRUE deep cycle. My 6 volt battery tray would probably hold another couple 6 volt batteries and I could probable get a couple more down in the 12 volt tray too, if I got rid of one of the 12 volt (I always use the dash switch to start anyway). So 6X 6 volt would be my goal if and when I put in a solar system.
Oh, and you are welcome! Nice to know you get something out of my posts.
Thanks Jim I appreciate your writings.
You are welcome, glad you like them.
I took a lot of flack on the Beaver Club forum when I mentioned the oil in the wet cells thing. I am tired of the corrosion on the tray, esp. as batteries age and demand more charging effort by the inverter, causing even more gassing and resultant corrosion. I found the best price on AGM’s at Batteries Plus Bulbs, Duracell’s. If wet cells, Costco’s Interstates are less than $100@. For a bit over $1500 I can get 2 chassis and 4 6v AGM’s at Batteries Plus and never deal with watering or corrosion again. Still, that is ~$800 for those niceties when maybe a little top-oil would do.
Ask them for proof that mineral oil harms anything in a battery.
It’s your money, but $800 is a lot for an expendable. I can replace all 4 of mine for under $360 at Costco. And I don’t mind the once every 6 or 12 month water fill. And at my age, I’m not sure I’ll be still RV’ing 12 years from now. I can nurse and cajole a wet cell battery with oil to give me 12 years I think.