Which battery bank is defective?

[danhaun]

Originally Posted by hzcruiser

OP mentioned "flooded 6V in series", so no LFPs. But yes, if set to "both" they have to show the same voltage, unless something else is wrong.

Since he's checked the contacts and cables, it's most likely that one cell on his second battery is shorting or highly sulfated. That explains why one batt is taking 5x more current but is not giving anything back.

Keep them separate and run off batt 1 as the faulty one will just drag the better one down.


Two 6V batts in series make a 12V batt, not really a "bank". Batts or cells in series would make a bank, but that's just semantics.

The OP might even have a complete separate starter batt. One would hope so if the voltage is around 12.1-12.3 in the morning.

I can clarify. The total house bank is 4 X 100+aH 6V flooded for over 400aH total but it is in two locations port and starboard (it is a catamaran) with selector switch that is always set to 'both" to yield one large enough bank (we do have refrigeration). Again, it has worked this way for many seasons now. I did remove one 'bleeder' from bank 2 and I do not see any other unless the original owner has done something (but I doubt that because everything else seems to be done right on this boat).

The starter battery is isolated and not involved. I am only concerned about the house.

My hunch is that hzcruiser is correct and I am changing settings to give bank 1 (or battery 1) 90% of the solar yield to try and get it to full charge.

Thanks for all the useful comments.

Dan

[Pete7]

Originally Posted by danhaun

I can clarify. The total house bank is 4 X 100+aH 6V flooded for over 400aH total

If they are wired to provide 12v then you have 200AH.

Pete

[danhaun]

Originally Posted by Pete7

If they are wired to provide 12v then you have 200AH.

Pete

I did not realize that. I guess I have something else to learn... keeps happening somehow.

Thanks,

Dan

[Cadence]

My bad and several overs. We read into it your start battery was one of your sets and you did not say that.
Sorry

[Jd1]

With 200 Ah of capacity and refrigeration on board, there is no doubt in my mind that you have reached end of life on your batteries! Make sure you change both sets of batteries even if one set is still 'sort of' functional. The old battery will drag down the new battery if they are not changed together.
Any place that does substantial business in batteries will have a tester that can verify (to some degree) if the batteries are shot or not.

[danhaun]

So after following all the guidance and isolating both and testing both sets under load, it is bank 1 that was depleted in a matter of three hours. I'm getting by on bank 2 for now by shutting down refrigeration for a few hours at night and headed for battery replacement ASAP. And yes, I will replace all four.


Thanks again to all who commented.

Dan

[thomm225]

Originally Posted by Cadence

A knowledgeable person knows in battery troubleshooting it's drop not measured voltage. And yes a VOM is indispensable for DC or AC troubleshooting just not for batteries, on their way out, without a load. A battery is a big capacitor.

A VOM is all you need to test the batteries if you know how to troubleshoot.

If you know how to troubleshoot, you will be taking measurements with the batteries under load and totally disconnected (off load/ open circuit)

Since you would check your connections anyway you can take some measurements at that time (no load)

I just had this problem during this past week and the batteries would not charge above 12.5 when they normally are at 13.7 float.

My panels check at around 18-19 volts with no load so they were good. (partially sunny day)

My problem was three cuts/partial cuts in the wire from my largest solar panel. In the right position the panel would work sort of and when the wire was test it showed good .........sometimes

I rewired the panel 2X before I cleared up al the breaks then hooked up the first battery which I let charge all the way to 13.7 before hooking them back to parallel

We used to watch this guy from Hewlett Packard (HP) troubleshoot live DC Circuits on power supplies with a VOM back in the day on film in electronic school. This back when techs still did component level repairs

His name was George something. He had the narrow tie, Brylcreemed hair, and pens in pocket a protector! The film appeared to have been made in the 60's since he looked just like a NASA Engineer of that era

[Dadrock33]

Check out the new carbon foam batteries at https://www.bruceschwab.com/advanced...asis-group-31/ Also known as the Firefly Oasis batteries. Read the specs and I imagine they'll be your next purchases . . . expensive? - yeah, a bit . . . but with those specs, you're in!!

[stormalong]

While you are replacing the batteries I suggest you do two things:


1) Hard wire them all together. That way you eliminate the 1-2-both switch that can accidentally be put in the wrong position. A simple on-off switch should be put in it's place.


2) It is time to do a power usage evaluation. 100 amp hours is not a lot of power. Especially if you have refrigeration. Of course the amount you need depends on how you use your boat. A larger battery bank means lower depth of discharge and longer battery life.



For reference I have 880 amp hours of capacity, the bank is now eight years old and still going strong.


BTW: you should have a fuse or circuit breaker within eight inches of the battery. This is an ABYC requirement. Your insurance company could make life difficult for you if there is a problem and you do not have one. If the two halves of your battery bank are separated one fuse per half is appropriate.