Batteries

[HJ Rosch]

I have a 2018 Alante 31V that has one 12v lead acid battery for the house battery. I don't do a lot of boondocking but am planning a 2-1/2 month trip to Alaska this summer and thought adding another battery might be helpful. The easy and less costly way is just to add another matching 12v lead acid battery. My existing battery is one year old with minimum use. I keep it filled with water and charged so I don't think there will be a problem with it being "old" and not compatible with a new one. What do you think?

[WinnieView]

Is it a true deep cycle battery? What is the lowest voltage it has seen? Could it be used as a spare chassis battery?

It is usually recommended that two batteries match in ratings and age.

We changed ours a few months ago as we often do and replaced two 12 volt with two 6 volt. The only pitfalls are available space and if only two and one fails that could be a problem. But our amp hours are doubled.

[Mustang65]

As WinnieView mentioned in the previous post, it is not recommend to add a second battery to an existing one that is not the same age, mfr, and Ah rating. The age factor along (with previous use) alters the internal resistance in the battery. So, an old battery will have a different internal resistance than the new battery. This means that the charging/discharging characteristics between the two batteries will be different. One battery will charge faster than the other and can over charge, while the other battery may not get fully charged. Also, in a short time the newer battery will take on the same characteristics as the older battery, which means lower Ah's/life.

It is best to replace both batteries at the same time with batteries that are the same and have a mfr date within a couple months of each other, at the most.

If you do go with 2 batteries, the picture below shows you how to wire them for the best performance.

Don
My Registry

RVing with SOLAR

[HJ Rosch]

Thanks for the info. I will be digging my coach out of the snow in about two weeks and I will have the existing single 12v battery completely checked out. If it is in "good" shape I will probably do nothing until it is starting to fail and then put in two 6v matched batteries. I have been starting the engine and generator every 2-3 weeks all winter to keep everything charged. Inspection will tell me what to do.

[Belvoirlist]

Can you send a actual picture of you Home batteries?

[Vicr]

Take your battery to a battery shop and have it "load tested" to find out its real condition.

[Barrick]

Originally Posted by WinnieView

Is it a true deep cycle battery? What is the lowest voltage it has seen? Could it be used as a spare chassis battery?

It is usually recommended that two batteries match in ratings and age.

We changed ours a few months ago as we often do and replaced two 12 volt with two 6 volt. The only pitfalls are available space and if only two and one fails that could be a problem. But our amp hours are doubled.

Why do two 6v batteries and not two 12v batteries? Is there an advantage in having 6v over 12v?

[Vicr]

Originally Posted by Barrick

Why do two 6v batteries and not two 12v batteries? Is there an advantage in having 6v over 12v?

There used to be an advantage to 6v because they had heavier plates and had higher ah ratings than 12v batteries but since the advent of solar and the sailing community there are manufacturers making 12v deep cycle batteries with ah ratings that rival those of 6v. The problem is many battery buyers aren't doing research into what is currently on the market and think if they see CCA on a battery it isn't a true deep cycle. Wrong, the sailing community is very interested in CCA in their true deep cycle batteries for the seldom times they need to start their engine.

[WinnieView]

Originally Posted by Barrick

Why do two 6v batteries and not two 12v batteries? Is there an advantage in having 6v over 12v?

"Wiring two 6 volt batteries in series is a cost effective way to obtain a higher amp hour rating and extend battery life between recharges. You'll find that the amp hour rating of two 6v batteries greatly exceeds that of two 12v deep cycle batteries wired in parallel. Using 6 volt batteries and wiring in series results in a 12 volt system without sacrificing amp hour ratings."

The 'disadvantage' is that if one of the 6v batteries fails there is no recourse to wire around it.

[Mustang65]

Originally Posted by Barrick

Why do two 6v batteries and not two 12v batteries? Is there an advantage in having 6v over 12v?

6 volt batteries have more life-cycles than 12 volt batteries. Here is how Trojan rates their life-cycles for their batteries (in red bar).

Also, a memo from the Trojan Support regarding 6 volt vs 12 volt.

Don
My Registry

RVing with SOLAR

[DNelson]

I decided to use my boats 12V trolling motor battery as a back-up in my 5th wheel 12V battery. I ordered and wired in a switch from Amazon that allows me so select battery 1, battery 2 or both. I simply periodically switch from battery 1 to battery 2 and back again to be sure both are fully charged as we travel. Some day I might put in 2 6V batteries but for now this works fine and the age and the ratings of the two batteries doesn't matter.

[Finemess]

Has anyone replaced there Gr27 deep cycle batteries with Gr31 AGM's
Is the charger capable of maintaining the AGM's

[rmhopper]

I just replaced (the horrible) single 12v Group27 battery in my 2016 Alante 31V with two Group31 12V deep cycle. I would have preferred to go with 6V, but the existing battery tray will only fit special-order 6V's and I didn't want to wait. Been out 4-5 times on the new batteries, both boondocking and otherwise, and they are working out fine.

[Vicr]

To get truly educated on batteries and not just repeat what others have said across the various RV forums this is a must read:


https://marinehowto.com/what-is-a-deep-cycle-battery/

[rmhopper]

Totally agree with you, Vicr, and I meant to imply I would have gone with 6V true golf cart "deep cycles" except that GC2 and GC12 batteries are slightly more than 7" wide, and Jayco in their infinite wisdom welds 14"x14" trays in their rigs, so it is significant surgery to fit proper 6V's in place for me. I can limp along with this for a couple of years while I work out a better mounting system for the right batteries. The question from Finemess was about the capacity of the house charger to handle dual Group 31's and that certainly isn't a problem.