Question on battery charging

[dockmasterdave]

I have 2 wallyworld group 24 deep cycle marine. I know this is not the same as 6 volt GC batteries, and I don't want those. We usually don't boondock but want the ability.
I recently upgraded from a wfco 45 to a PI 55 amp. I also upgraded my wire to 10 ga, max run is about 15'.
It has worked fine for several months ( not using the TT due to covid closures etc ).
Yesterday I smelled a sewer gas smell at the front of the tt. My tanks are in the rear. Opened my compartment and 1 battery appeared to have boiled out some water and was warm to the touch, with bulging sides. I immediately disconnected both batteries and removed the offending one completely.
Both batteries were purchased in 2018. The bad battery tests at 10 volts or less resting.The other battery appears fine and voltage tests fine.
Is it possible a cell went bad or a battery went bad and caused overcharging ? If so , why did only 1 battery overcharge ?
I want to make sure I didn't connect something wrong while upgrading charging circuit.
I added a new circuit breaker and jumper wires from plus to plus and minus to minus,and new cables to the circuit breaker and from circuit breaker to junction box where tt already had 10 ga.
Sorry this is so long, but I know people always want more specifics.
Opinions greatly appreciated, especially from the 12v gurus.
TIA

[MEXICOWANDERER]

THE OLD GRAY MARE AIN'T WHAT SHE USED TO BE

It isn't uncommon to run into a bad battery. Some fail right at the battery plant when filling with electrolyte. They bubble over and smell like Yellowstone National Park.
Not uncommon when plate paste goes sour. Immediate drama upon filling or greening

[pianotuna]

Hi,

Marine cycle batteries are poor at deep cycle use. I suggest upgrading to an SiO2 chemistry.

The other battery is most likely compromised.

[johnhicks]

My two Wallyworld group 27 marine/rv batteries lasted 11 months. I checked the water every month and never had to add any. They still don't need any water added.

The 12v lights got a ittle funky one morning, I checked the voltmeter and saw 10.5v (!) and of course there was that nice smell in the compartmnet.

The batteries looked fine but both had a little water on top. I yanked out the easiest one to get at, and in short time the other one was almost 12v and climbing. It went into float at about 13.1v The other one sitting on the ground showed 11.8v the next day.

I got another battery and installed it as a single; it's at 13.1v. This is liveaboard usage every day.

So...my previous Interstate group 27 marine/rv batteries lasted six years even including a couple of instances of abuse. The Wally batteries, ostensibly the same, lasted 11 months. Hardware and usage is the same.

[theoldwizard1]

dockmasterdave wrote:
Is it possible a cell went bad or a battery went bad and caused overcharging ? If so , why did only 1 battery overcharge ?

You will never know why that one battery took a dump.

Personally, I do NOT believe in leaving lead acid battery connected to a charging source 24/7 weeks/months at a time. If possible, wire in a cheap mechanical lamp timer and only charge for about 4-6 hours/day. You battery will last longer !


Whey so negative on a pair of 6V golf carts batteries ? They are typically cheaper than a pair marine/RV 12V and usually last longer.

[Matt_Colie]

Dave,

As you correctly surmised, the hot boiled battery is toast. But, if you don't really need two batteries to make it through the night, don't replace then until the start of next season. Batteries are a mostly a calendar problem. If you end up doing a lot of dry camping or boondocking, then go the GC2s route. They do work better and longer.

Matt

[time2roll]

The battery is shot

That #10 s/b #6 or #4. Make sure you replace the entire loop including the ground connections at the battery and converter/ power center.

[corvettekent]

It sounds to me that you did not check the water level in your batteries. When the level gets below the lead plates you toasted the battery.

[CA_Traveler]

Batteries can fail in 2 years or less. A shorted cell means that the 5 cells will be overcharged, bubble etc. and your 10V suggest a shorted cell.

Replace both batteries as no doubt the "good one" has been stressed.

And look up balanced wiring in case your batteries are not wired that way.

[BarneyS]

I think this question fits better into the Tech Issues forum rather than DIY and that you will probably get more response there from 12V.Gurus. :W. Moving to Tech Issues from DIY.
Barney