Two, 12v batteries, service question

[MTPockets]

I regularly check and add water when needed to both of my 12v batteries. Batteries are now 4 yrs old and work like new. When needing water, only one battery needs water most of the time while the other rarely needs water, and then only 1/4 the amount of the other. Both batteries recently checked 13.3 volts when disconnected. Any thoughts on why there would be a difference in water need?

 

[windviewer]

Check to make sure the way the batteries are connected follow the explanation found at http://www.marxrv.com/12volt/12volt.htm

http://caravanchronicles.com/guides/how-to-connect-two-batteries-in-parallel/ is also good reading material.

 

[Bohemian]

All batteries arte different. It is always best to run a system where all batteries are the same brand, model, and manufacture date with the same history. Even then they will be different. They will each have a different "strength". One battery will tend to discharge the other batteries in order to stay at maximum charge. They will all charge at different rates and develop differing amounts of heat and vaporize off water at different rates. 2-6V batteries in series will see less of this (or in principle "can not do this") as compared to 2-12V batteries in parallel.

So the real practical question is how much do they differ? If these are all small routine amounts of water and the batteries each separately are in good condition, then everything should be just fine. If when connected together off a charger one stays good and one discharges a large amount, it may be time.

 

[Jesstruckn/Jesstalkn]

Very curios if your +positive and -ground cables are on the 1 battery using the water. Or are the connected correctly like the diagram in Windviewer's link ?

 

[Lynn1130]

I am not sure about the water use but I will tell you that batteries that are 4 years old in AZ is a rarity. My golf cart batteries just croaked and they were just short of 4. That is the longest that I have had any battery last except one of the Japanese quad batteries that made it 10 years and I have no idea how that happened. It was sealed and always on the Battery Tender when not is use.

So the point here is you may want to check cells to be sure that one or more is not weak and drawing more that it should trying to charge.

 

[MTPockets]

I am not sure about the water use but I will tell you that batteries that are 4 years old in AZ is a rarity. My golf cart batteries just croaked and they were just short of 4. That is the longest that I have had any battery last except one of the Japanese quad batteries that made it 10 years and I have no idea how that happened. It was sealed and always on the Battery Tender when not is use.

So the point here is you may want to check cells to be sure that one or more is not weak and drawing more that it should trying to charge.

. Haven't checked yet for proper connections, but will in next couple days... AZ heat no problem cuz we're gone when it's hot. We're full time too, so batteries are always charged.

 

[JohnD]

You might try swapping the batteries and see if the other battery does the same thing in that position.

 

[MTPockets]

You might try swapping the batteries and see if the other battery does the same thing in that position.

John! Great idea. I'll do it tomorrow.