Correct multiple battery configuration.

[Wolf8U]

Read more than post, I learn more that way it seems. I had to replace the coaches batteries, 2016 Thor Hurricane 34F, the previous batteries were 12v flooded and I replaces with 12v AGM. My question is what is the correct configuration for the series of batteries? I put the new ones inexactly as the old ones were. However doing so I started thinking it didn't seem right. the 1 and 3 battery had single connections, the two and four had multiple connections. We bought this used and have no idea how the arrangement was done by the previous owner, whether he did it or paid to have it done. Anyone running four 12v in a configuration that is correct? I've watched a lot of youtube videos but most skip the configuration on four 12v. May i see a picture of how it is wired please with written configuration of wiring including the hookups from the coach. I've gone through the manual I got but there was nothing in there regarding this.

[Lt Keefer]

No help here, I have 2 batteries not 4. But I am starting to research my next set of batteries. What brand and where did you buy the AGMs?

[Wolf8U]

Advanced Auto on sale, can't remember brand but maybe I can get a picture before the weekend.The true and only reason for the AGM batteries, well I'm lazy and didn't want the maintenance or the leakage, the old batteries were sizzling and leaking.

[Bob Denman]

I would imagine that you want 12 Volt power coming out of them.,.
Wire them up so that you're always connecting positives to positives; and negatives to negatives.
You should have positive and negatives coming in, a nd going out... Just continue that theme all the way through.

[Lt Keefer]

Thanks Wolf. I'm like you, tired of the mess in the battery compartment. I spent 2 hours today cleaning and watering. If the batteries were dead, they'd be gone.

[Travelin' Texans]

To connect multiple 12 volt batteries "parallel" you should have positive to positive negative to negative from 1st to last battery with a positive from battery #1 & a negative from #4 that equals 12 volts at those positive/negative cable ends.

[Bob Denman]

https://www.thorforums.com/forums/at...1&d=1595330702

https://www.thorforums.com/forums/at...1&d=1595330702

[TurnerFam]

typically, 4 batteries in an RV motorhome would indicate 6v batteries, and wired in SERIES, and then PARALLEL, for 12v output... but only YOU can determine if you actually have all 4 12v batteries, as you suggest...

[Bob Denman]

We've got picture for that also...

https://www.thorforums.com/forums/at...1&d=1595341538

[Travelin' Texans]

If there are 3 caps on the top of each battery they're 6 volt, 6 caps they're 12 volt.
It needs to be determined how many of what voltage you have to determine the correct wiring to get to 12 volts at the end.

[lwmcguire]

After you determine the battery voltage and connect them correctly the positive and negative to the Chassis should be connected so the entire bank is utilized, don't have a drawing handy but easy to figure out after looking at the tops

I went to Trojan T105 AGM's last spring and it is the best thing I could have done to eliminate a lot of messing around and busy work. they hold voltage very well during down time and handle all the load we throw at them

[JoeDS]

You can indeed wire 4 12V batteries in parallel.


HOWEVER it would be VERY wise not to mix battery types and I would replace all 4 at once with the same kind. You don't have too but an old battery can bring down a new battery.


Heres why. If you have 4 batteries in parallel and one of the 4 has a weak cell that reduces its voltage slightly the other 3 will attempt to "charge it" when you are not connected to a charging source.


Eventually they will discharge down to a deep discharge state that will actually damage the "good" batteries also. The time it takes varies greatly but it will happen. If one of the batteries has a cell "short" then you are in for some real interesting but not fun results such as a fire or exploding battery.
If you do connect 4 batteries in parallel I would put a high current fuse on the positive leg of each battery just for safety.


One other thought is group size. My Vegas originally came with two group 24 sized batteries. I replaced them with two group 29 batteries which allowed me to greatly increase my Amp-hour rating in the same available space. (Due to insufficient height available I could not fit two 6V "golf Cart" batteries in series which if possible is the best approach)

[lwmcguire]

We ran GEM cars for many years with 6 12v gel or AGM batteries

With your charger shut off and a good digital volt meter you can check the voltage of each battery without disconnecting cables

Simple way to ferret out a failing battery

Due to the 300 bucks per battery and having 12 to monitor between the two cars I didn't replace them until necessary

And contrary to all the battery experts I often replaced one and the rest of the bank went on to perform for several years

Currently the 4 T105 AGM's are on their second year and performance is significantly better than flooded albeit at a price

[JoeDS]

Originally Posted by lwmcguire

We ran GEM cars for many years with 6 12v gel or AGM batteries

With your charger shut off and a good digital volt meter you can check the voltage of each battery without disconnecting cables

Simple way to ferret out a failing battery

Due to the 300 bucks per battery and having 12 to monitor between the two cars I didn't replace them until necessary

And contrary to all the battery experts I often replaced one and the rest of the bank went on to perform for several years

Currently the 4 T105 AGM's are on their second year and performance is significantly better than flooded albeit at a price

Were those in series or parallel? Series is the best way of course . Real easy to check especially under load. In parallel the only way to really check is with a hydrometer (on a wet cell- old school but will clearly find a weak cell)

[lwmcguire]

GEM cars are 72 volt

Voltage test will work no matter the configuration, give it a try

Must have a good VOM

[JoeDS]

Originally Posted by lwmcguire

GEM cars are 72 volt
(sounds like a series connection to me)
Voltage test will work no matter the configuration, give it a try

Must have a good VOM

Not true on a parallel configuration unless you isolate each battery.

Ohms Law has not been disproven so far.

A hydrometer will test each wet cell no mater what.


As for "giving it a try" I way a Navy electronics technician for 13 years then an electrical engineer for 35 years. Ive used a VOM quite a few times.