Battery Maintenance Pt 2: Boil Over

[Travelling Three]

Again, I have a 2017 Montana 3661RL with two batteries wired in parallel. Previously I wrote about a possible leaking battery. What I discovered is one of the two batteries has boiled over. The six cells has enough water in them but I can see where water has leaked from under the cell cap. What causes the water to boil over and can this be prevented?

[WeBeFulltime]

Sorry I can't say how to prevent it but I have never had the problem over 12 years and 3 different new Montana fivers. Maybe converter over charging?

[Theunz]

I had both of mine boil over once. After I removed the batteries to clean them up I found that I had over filled them. It's hard to see the level with them installed, so be judicious when filling them. I have had no trouble since, and that was about a year ago.

[AZ Traveler]

You could also have a bad battery.

[jcurtis934]

Most times the battery/batteries are what cause the converter to keep supplying excessive charge current. If you didn't use distilled water in them, added a new battery to the bank without changing out the existing battery, or batteries are over three years old for normal cheap deep cycle...then it's probably time to replace. Given a 2017 rig, batteries should just be 3 yrs old and we know dealers don't install quality batteries. Just shooting in the dark here.

[DQDick]

My solution is to get a couple of good AGM batteries.

[h2ojocky]

With your year rig you should have a smart charger/converter, which should not allow over charging. I have 2-6volt golf cart batteries and have had real good luck with them. Many on this forum have switched to golf cart batteries. I don't know if you do any boon docking but if you do I think you will like the 6 volt golf cart batteries. I only have 2, but some have 4 or 6. Whenever you replace a battery always replace all batteries or the old battery will draw down the new battery.

[mazboy]

if you didn't over fill you probably have a bad battery. replace both of them.

[ChuckS]

Use a multi meter and measure output of converter at battery. If it’s higher than 13.8 then most likely shorted of dead cell in battery. To verify disconnect converter from battery and measure output of converter. If 13.4 to 13.8 you know converter is good

[laverdur]

Batteries can fail at any time but starting with good batteries can go a long way to getting good battery life. My Monty came with two Centennial Group 27 deep cycle, maintenance-free batteries (DC27MF). These are standard flooded lead-acid batteries. The key is that they are truly maintenance-free. My rig stays plugged in to shore power or the TV all the time except when it is in the shop for annual axle service. I got 6 years of reliable service out of my original batteries. Last year I had to replace then with Interstate batteries. They were also deep cycle batteries but they were not maintenance free so it required checking electrolyte levels every 90 days. Not a huge problem - just an annoyance. After 11 months with the Interstate batteries, I remove them and put new Centennials back in after having the batteries discharge to the point of tripping the 50 amp breaker for my hydraulic slides after being off shore power for 8 hours while a window was being replaced. Never had the Centennials do that. And yes, I've seen all the posts about upgrading the auto-reset breaker to 80 amps. I did that yesterday. I'll sell the Interstate ones for whatever i can get. Someone can use them for a trolling motor or some other low current purpose and they will do just fine.

[cgeis48]

What AGM Battery AMP/Hour rating is best. I found a load of choices and prices on a web site: https://www.batterystuff.com/

[AZ Traveler]

Originally Posted by cgeis48

What AGM Battery AMP/Hour rating is best. I found a load of choices and prices on a web site: https://www.batterystuff.com/

Carl,

It really depends on how you use your rig, if you have an inverter, a res fridge and ever boondock even for a few hours.

The smallest battery bank I would consider is 200 AH or 400 AH if you plan any boondocking with an inverter.

[DebNJim B]

I bought a 1 year old RV once and the dealer installed a new battery and gave me the old one. I hooked them up in parallel and ran that way for a couple years. Then one night in the middle at about 2 Am the gas detector went off. After a brief search I found the older battery was boiling over and the hydrogen/sulfur gas set off the detector. I guess a plate warped and shorted out but I never had it tested, I just discarded the battery. I later learned (from this forum) that you should always use matched batteries if you run in pairs.