battery water going low on only 1 battery

[Wayne67vert]

I have 2 12 volt house batteries. I had one of the batteries get low on water while the 2nd is ok.
Is there something I should look for to correct this or is something I have to put up with?

I have a 2002 Holiday Rambler on a Ford E450 chassis

[wa8yxm]

First if the battery has a CCA rating (Cold Cranking Amps) or an CA or MCA rating (Cranking amps or Marine cranking amps) it is MOST LIKELY a starting battery not a true deep cycle (Thoguh there is no reason not to computer the cranking amps for a Deep cycle, that's not their primary use so it's not common)

With batteries in paralles. if one is "Very thirsty" compared to the other, there are only two (well 2.2) possible answers
1: Bad connection, only one battery actually in use, other just taking up space
2.1 One battery failed: High resistance, Just sitting there taking up space
2.2 One battery failed, Shorted cell, sucking up water as a result.

In either case, Take 'em out, Charge them one at a time and haul to Auto store for testing.. Replace with a pair of GC-2 Six volt Golf car batteries in SERIES 230 amp hours at 12 volts, cost about the same as 150 amp hours of 12 volt type and are TRUE deep cycle.

[landyacht318]

Drat, marketing wins again.

2 of those duralast 12v marine/dual purpose batteries are More money for less capacity, compared to the Eastpenn/deka golf cart battery I linked from Batteries +





12v dual purpose battery on left, 6v golf cart battery on right:


Source:
http://www.pbase.com/mainecruising/deep_cycle_battery

[pianotuna]

For Marine batteries depth of discharge for greatest number of cycles is quite shallow. For a 100 amp-hour jar, only 20 amp-hours should be used.

[Wayne67vert]

Here are the specs:

Duralast battery

I like AutoZone batteries.

[landyacht318]

I see no autozone duralast battery with 845CCA, I'll stick with my guess.

[pianotuna]

Landy it is not a delco nor a duracell. It is a Duralast 845. Probably a group 29 12 volt jar.

[landyacht318]

Nope, just marketing mumbo jumbo

googling duracell 845 yields this:

https://www.batteriesplus.com/replacement/battery/ac-delco/845a/sligc115

Looks like a East Penn/Deka golf cart battery at 230AH

Genuine upgrade.

[pianotuna]

Hi,

The new ones sound as if they are either Marine or Starter batteries. These do not last well when deep cycled.

845 may be the cold cranking rate.

What is the 20 hour amp-hour rate?

[Wayne67vert]

I had 1 bad battery and the 2nd had a bad cell. The best battery was dated 3/15 and the other had no date. They were not matched batteries.
So much for the seller telling me that he put new batteries in.
I up graded to 2 Duralast 845 amp batteries.
These should hold for a long time.
I do have a new converter with smart load.

[Wayne67vert]

Thanks for the replies.

I'll let you know how they check out.

[RoyB]

Glad you are checking your batteries...

Two things to look at...

What is your converter/charger unit. Being an older trailer chances are it is a single mode 13.6VDC charger... You really should replace it if this is what you are using for a more modern multiple mode smart mode charger type. Progessive Dydnamics or IOTA brands are tops... I would not get a WFCO product as they are known for not going into smart modes when needed. It is well known that having 13.6VDC being applied to the batteries for long periods of time will cause boiling out fluids. This will eventually cause the battery to have an internal cell short which is not recoverable and require replacemnt.

Another thing would be to make sure you are using a balanced connection to your two 12VDC batteries wired in parallel.

Use a wiring scheme like this using equal lengths of cables inside the battery terminals... This insures both batteries demand the same DC current when being charged...



Continue to watch your battery fluid levels on a tight schedule until you make corrections like discussed here...

Just some of my thoughts here...
Roy Ken

[MEXICOWANDERER]

"Nehhhh"

Check charging voltage. If above say 13.4 and it's a 75 degree day the voltage is too high. Battery #2 could have an open cell.

If charger voltage is normal then suspect the thirsty battery as having gone bad. Test it.

If the "good" battery is more than a year-and-a-half old you should replace both. You can have a hundred batteries on a charging line. Twenty can be bad. The good batteries will not suddenly start using a lot of water

If you play
Eat one now save the other for later...

The old baytery will eat the new battery. Fiscally a poor choice. Boiled-down there isn't really advantage in testing unless the batteies are recen

[BFL13]

If you have the two wired so that one has the "load and re-charge" wires on it while the other is "downstream" then that might explain it if the one with the load wires on it is the one losing water more.

That would be from it doing more of the work than the other.

Or it could be just going bad.

[Chuck_thehammer]

a bad connection. or bad cell in one battery.

remove both batteries.. charge them.. then take them to an auto parts store..

request a 100 amp load test be done on both batteries.

if both batteries are OK, check all connectors and cables.