Battery Boil & Water

[S/V Adeline]

Originally Posted by sailorboy1

theories as to why battery 2 boils over and uses more water than the rest

If you relocate the batteries does the boiling follow or does the new battery in position 2 start boiling?

[sailorboy1]

Originally Posted by S/V Adeline

If you relocate the batteries does the boiling follow or does the new battery in position 2 start boiling?

I was wondering the same. May give it a try to see next week when i have time.

So far no one has answer the question of whether a shorted cell wouldn't/would show up as reduced capacity of the entire bank.

[a64pilot]

Yes a shirted cell will reduce capacity of a bank, and of course over time it will discharge a bank much faster than its normal self discharge rate.
However if there is little to no rest period for the short to drain the battery the reduced capacity may not be much, if put straight into use right after charging, the short may not have enough time to reduce capacity a whole lot.

It’s been years since I played with wet cells, but I thought I remembered that the shorted cell was the only one that boiled when you were charging it.

This may help explain a short
Causes and how it acts etc
https://batteryuniversity.com/learn/...internal_short

I believe the “boiling” to actually be electrolysis, the water is being broken down into hydrogen and oxygen, and I thought the shorted cell due to its short would both get hotter because more power is being consumed there due to the short and as there is more power, there was more electrolysis. In other words a shorted cell boils more.

[Dsanduril]

I’d wonder if the problem, whatever it is, is in battery 1?

Water use/boiling could indicate over voltage at battery 2, is that because in that series pair battery 1 is at a lower voltage?

What does battery 1 SG look like when the bank as a whole is showing full charge?

[sailorboy1]

Its been this way over 3 years and the bank does not appear to have lost any capacity. So I'm not accepting the shorted cell “reason”.

[s/v Jedi]

Originally Posted by sailorboy1

Its been this way over 3 years and the bank does not appear to have lost any capacity. So I'm not accepting the shorted cell “reason”.

What you accept or not is irrelevant to your battery bank in real life. As long as you fail to diagnose the cause by following recommendations, you can ramble on about it to eternity

For me I need to know if my battery bank is healthy and ready so I would get out the tools and do the diagnostic, then fix whatever needs fixing

[sailorboy1]

Thanks for the very useful post

[Dockhead]

You could be more forthcoming with useful information, couldn't you?

The reason why a shorted cell would cause the whole battery to boil out is that the CELL LEVEL VOLTAGE is increased on account of the missing cell. If you are trying to charge a nominal 12v batt at say 14v, then instead of 2.33v per cell you will be giving them 2.8v per remaining cell - as if you were charging a normal battery at 16.8v. That's why a batt with a shorted cell will boil quickly and can even start a fire.

One more reason why I dislike this 19th century Dr. Frankenstein style technology.

But that's not the problem here - batts with shorted cells can't last that long.

Originally Posted by ramblinrod

Nope.

[s/v Jedi]

Originally Posted by sailorboy1

Thanks for the very useful post

The useful one was my first post, which you ignored. It would have taken care of your problem, limit possible damage to the other batteries and not lead the thread the way it’s now.

I guess it’s nice to ramble on forever about something without doing anything to fix it, but I don’t care for that and just tried to get you going.

[chris95040]

Me, i’d start with a somewhat full charge, disconnect all the batteries from each other, let them sit a couple hours, and measure the idle open circuit voltage of each. That way i’d have some initial information to go on.

Or just present incomplete information and be vaguely snotty with people trying to help..

[sailorboy1]

I gave all the info

just disregard the question

[S/V Adeline]

Picture each individual cell as a ladder, 10 rungs.

One leg is '+' the other is '-'

Top rung is '1', bottom is '10'

Cells are connected at the top.

If there is a short between rung 9-10 you will still have 95% of that cell. A short between 5-6 leaves about 50% working as a cell. A short near the top, dead short, would drop the entire cell and whatever voltage it carried.

Not a perfect analogy, but the ideal visual for how a short can diminish amp capacity.

[sailorboy1]

Dont have a capacity loss

[kenbo]

My hypothesis, since the behavior of the bank has been consistent since installation AND there has been no significant loss of capacity, I posit that #2 has a lower internal impedance than the other 3. This results in more current flowing through #2 and more power to produce increased hydrolysis.

But every hypothesis needs to be tested.

[S/V Adeline]

Measure the voltage drop through all connections, series and parallel. Measure the final ground of the series to the common as if it were two parallel batteries.
Any drop should be documented on your diagram.
Then remove all connections, fully charge and test each battery individually. They won't all be identical. Measure resistance of each cable. Measure resistance across each battery.
You will probably have your answer at this point, batt 2 may have always been slightly smaller in capacity(my guess). Could have a cable with resistance issues. Cable end issue. While everything is apart is the time to clean all connections.
These new fangled battery testers give a computer printout down to the exact amp capacity, not sure how much I trust those but I would have all four tested for comparison.
If there are truly no issues found, install the suspect battery in a different location and observe.
I have six 6v batts in series, seems like there are always voltage drop issues. Cables different lengths, which adds to those issues.
Unless you are using the full capacity on a regular basis, a 5% drop in a single cell would probably never be noticed. I recently replaced a 12v car battery that was working fine. No issues until the car wouldn't start (fuel issue) and repeated attempts drained the battery too fast. Testing revealed the 500cca battery was down to 346cca capacity. More than enough to start the car and operate the systems, but most of the reserve capacity was gone.