Bad cell Sg?

[monte]

Hola. Just a quick question. I just checked the batteries (20 month old exide duel)
Most had specific gravity reading around 1.250. One cell read 1.175.
Battery monitor showing 90% charged, voltage 13.2V, 10A going in via solar.
A couple of batteries were low on fluid (just over the plates) so I added some and will check those tomorrow.
For now, the battery with the low sg cell...does it need immediate replacement or removal from the bank?

Charging is 100% by solar. We have the solar charger set to 14.8V for 12 hrs absorption. Most days we range between 75%-100% charged. Battery monitor seems close enough, we see the acceptance rate drop in the afternoons to 10-15A when around and over 90%.
The bank is 6 X 140Ah. 1150W solar and victron 150/85 mppt controller

[wrwakefield]

Originally Posted by monte

Hola. Just a quick question. I just checked the batteries (20 month old exide duel)
Most had specific gravity reading around 1.250. One cell read 1.175.
Battery monitor showing 90% charged, voltage 13.2V, 10A going in via solar.
A couple of batteries were low on fluid (just over the plates) so I added some and will check those tomorrow.
For now, the battery with the low sg cell...does it need immediate replacement or removal from the bank?
Attachment 117899
Charging is 100% by solar. We have the solar charger set to 14.8V for 12 hrs absorption. Most days we range between 75%-100% charged. Battery monitor seems close enough, we see the acceptance rate drop in the afternoons to 10-15A when around and over 90%.
The bank is 6 X 140Ah. 1150W solar and victron 150/85 mppt controller

Monte,

Are you able to equalize the bank and observe/reconfirm SG readings?

If that cell doesn't recover during/after an equilization cycle you may need to isolate that battery from the bank [from my experience- detailed below...]

When I bought my current boat in 2014 I ended up having to isolate two batteries (6vdc) from the bank because one bad cell in one 6vdc battery didn't recover after equalization. Two other cells in other batteries with equally low SG did recover.

I ended up replacing the entire bank 6 months later for my own piece of mind as it was only testing at 55-60% of original capacity... [I bought the boat knowing the bank was 7 years old and that the broker, on more than one occasion, had allowed the bank to completely discharge...]

Best wishes resolving this issue.

Cheers!

Bill

[wrwakefield]

To quantify 'recovery' for the low cell, per Boatowner's Mechanical and Electrical Manual [4th ed; Calder; p120]

...If the [SG] difference between the highest and lowest cell readings is >0.030, then the low cell is probably dying. And, if after recharging, the difference remains over 0.030, this cell is most certainly dying (in all probability shorted.) If the electrolyte in the hydrometer is murky, the plates are breaking up...

FYI in case you didn't have a reference.

Cheers!

Bill

[monte]

Thanks Bill. I'll attempt to equalise when the sun comes back. A bit difficult at anchor but will give it a try 🌞

[wrwakefield]

Originally Posted by monte

Thanks Bill. I'll attempt to equalise when the sun comes back. A bit difficult at anchor but will give it a try ��

You're welcome, Monte.

I hope it works out for you.

At least you have the solar array, controller, and, most importantly, solar exposure to get it done if it is possible...

Brainstorming, if you cannot hold the equilization voltage long enough to equalize the entire bank, perhaps you could try a second time by isolating the bad battery from the bank and only equaliizing it... [of course, the entire bank is preferable, but if you can recover that bad cell you are halfway there...]

Crossing fingers for you.

Cheers!

Bill