3 batteries. One uses water

[Chris142]

My old Peterbilt is just sitting lately so I have it on a trickle charger.

It has three 12v batteries. The starter cables are connected to the front battery and then theres jumpers to the other 2 batteries.

Every 6 months or so I pop the caps and check the water in the cells. The battery farthest away from the one thats connected to the battery cables has been low both times.

Why would this one use more water than the other 2?

 

[wrcsixeight]

I assume they are different makes/ brands?

I have a Walmart which has only required water once in 53 months. I have 2 Crowns which require water every 4 months.

They all see the same charging voltages within 0.05 volts.

 

[HTSS_TR]

Can you swap that battery position to the one that's connected to the battery cables to see if that battery still loose more fluid ?

 

[mechanicx]

Are the batteries the exact same type and size? I know in cars there are lead antimony low maintenance that use some water and then there is lead calcium no maintenance that use very little water. Or maybe the one battery is older and is discharging faster.

 

[Chris142]

Originally Posted By: wrcsixeight
I assume they are different makes/ brands?


No they are all the same bought at the same time with the same date code.
Originally Posted By: HTSS_TR
Can you swap that battery position to the one that's connected to the battery cables to see if that battery still loose more fluid ?
Ya but I'm lazy and they weigh about 100 lbs each.

 

[The_Jeff]

Lower internal resistance on the one that's drying out. Stop trickle charging and the water will stop disappearing. It could be slightly weaker than the others, or it could be boiling off as a coping skill.

You should probably undo the interconnects and wander out there weekly to switch which battery is getting tickled. It's not good for your good ones to be dragged down by the class clown.

 

[JHZR2]

Originally Posted By: eljefino
Lower internal resistance on the one that's drying out. Stop trickle charging and the water will stop disappearing. It could be slightly weaker than the others, or it could be boiling off as a coping skill.

You should probably undo the interconnects and wander out there weekly to switch which battery is getting tickled. It's not good for your good ones to be dragged down by the class clown.


+1

 

[dwendt44]

Usually, when a battery uses water at a fast rate, it's from overcharging.

Doesn't seem to be the case here.

IF all the cable connections are clean and tight, switching positions is the first step in figuring out what's up.

 

[berniedd]

How are the batteries connected? Series or in parallel?

 

[Chris142]

Originally Posted By: berniedd
How are the batteries connected? Series or in parallel?
I forget which is which. It's a 12v system and they are wired +-+-+ and --- so that it's got 12v but lots of cranking amps.

 

[Texan4Life]

it would be parallel as series would equal 36v. In my experience some batteries lose more water than others.

Though, if I was bored one day, I would take them out and have each one tested to make sure you don't have a dud that the others are trying to compensate for.

Most auto parts store will test for free.

 

[brianl703]

Originally Posted By: Chris142

It has three 12v batteries. The starter cables are connected to the front battery and then theres jumpers to the other 2 batteries.


Try this, if the starter cables are long enough:

Take one of the starter connections, either positive or negative, and connect it to the battery which is furthest from the other starter connector.

That is, if you have three batteries connected like so: (P-positive, N-negative)

P1---P2---P3
N1---N2---N3

And your starter is connected to the P1 and N1 terminals (battery 1)--connect one of the starter cables to either P3 or N3 (battery 3) instead. One of the starter cables should be connected to one end of the battery string and the other should be connected to the other end of the battery string.

This way of connecting the batteries equalizes the discharge current from all of the batteries when cranking the starter. It also equalizes the charging current as well.

What's happening now, with both starter cables connected to battery 1, battery 3 does not contribute as much of the starting current as battery 2, which in turn contributes less of the starting current than battery 1. Therefore battery 1 is more heavily cycled than the other 2, and battery 3 is the least heavily cycled.

 

[meep]

READ THIS--

switching order won't help.

the poster that said it's overcharging is on the right path...

The battery is weak, so it won't reach the same state of charge and therefore it won't "rest" to a higher voltage, like the other, healthier batteries are. It has more sulfation buildup than the others. So it stays at a lower state of charge and boils before it reaches the cutoff point on the charger.

IF YOU DO NOT TRICKLE CHARGE ALL THREE, THE LOWEST BATTERY WILL PULL THE OTHER TWO DOWN. So keep charging the trio and adding fluid to the weakest one. This is why it is generally recommended that parallel-connected batteries always be replaced together. If the weak one is always dragging the others down, they will age faster. BTW we are talking about measurements in the 0.05 volt range when we talk about aging batteries and their state of charge.

So-- my suggestion, keep doing as you are. If it makes you nervous and you want to pull the charger, disconnect the weakling from the other two.

M

 

[berniedd]

Yes I agree, disconnect the weakling from the other two. But trickle charge it too, but intermittently so it won't totally die. Reconnect it when you're going to use the truck, then disconnect again once you're done. Remove (and reconnect) only its negative cable.

Now you may trickle charge the other 2 on a less frequent schedule.