Faulty batteries or is it something else?

[Pdemajo]

Long read....Sorry

My 12V setup:
3 160Ah deep cycle AGM for service and 1 160 Ah Deep Cycle AGM for Starter. Battery bank 1 is my Starter and batt bank 2 is my services. One battery charger, 3 stage Dolphin SM series 40AH which charges both banks. One Victron BMV battery monitor. My service batteries are 1 year old. My starter battery is around 3 years old.

Last Thursday, after having left all batteries on charge for at least 48Hrs i decided to run a test on my service batteries. Whilst charging, the voltage of both banks is at around 14.3V.
I turned off the Starter battery. I turned off the battery charger and waited for the voltage of the service batteries to settle down. It settled at 13.2V.
I then loaded it with an average of 15Ah by turning on internal and external lights, fans, navs, invertor, etc. Not the fridges as it would not have been a constant draw. I recorded every 15 min the voltage changes. for the first 2 hrs the voltage drop was constant. After 1.5 hrs according to Victron, v=12.5 SOC=94% TTG=12.1.
As the 2nd hour passed i noticed the fan on the invertor slowing down. Victron said V = 10.8 and it would not give a reading for TTG and SOC. The service batts were dead. I switched off everything and the V went up to 11.2.

I then ran the same test on my starter battery (connecting it to my services by itself) and put a load of 5Ah (1/3 of 15) on it. After 8 hours it was still above 12.2 and recovered to 12.4 when i removed the load, so I deemed it good.
Since all batteries are charged simultaneously by the same charger I concluded that the charger is fine, my starter battery is fine, but my service batteries are faulty after 1 year.
Before claiming warranty, is there any other explanation that i should think of?
Thank you for taking the time to read this!

[S/V Illusion]

Hard to know definitively, however, I would start trying to narrow down the problem by testing each battery in the bank individually as one bad battery will affect the entire bank.

[sailorboy1]

[QUOTE=Pdemajo;3637779

Last Thursday, after having left all batteries on charge for at least 48Hrs i decided to run a test on my service batteries. Whilst charging, the voltage of both banks is at around 14.3V.
[/QUOTE]

The batteries went since at 14.3 charging after 48 hrs?

If the batteries were fully charged, and they should be after 48 hours, then you have a battery problem. By if the charger was doing 14.3 after 48 hours you also have a charger probem that may have caused it.

[CarlF]

AGM batteries can fail due to PSOC (partial state of charge) sulfation in a year. Before the recent charging did the batteries spend lots of time at less than 100% charge?

AGM’s are not a good choice for a house bank unless you normally plug into shore power or have enough solar to go to float most days.

If all three batteries have failed the manufacturer is likely to deny a warranty claim on the grounds the batteries were not kept properly charged.

If these are Lifeline batteries there is a procedure in the manual for a restoration charge that sometimes restores the lost capacity.

[Pdemajo]

Thats interesting... what should my charger be charging at when they are fully charged? Thank you...

[Pdemajo]

the boat is normally in its pontoon with the charger on. She was up on the hard for 6 weeks this year and in that period all electrics were off. I still plugged it in 3 times for a full charge to bring them from 99% to 100%
I dont think I have a problem with the charging part, but maybe I should put in a couple of panels to keep them always topped up....

[ItDepends]

It's a dead certainty that the three house batteries are toast. It might have started as one bad, but it has gone way past that.

As sailorboy1 has pointed out, if your batteries were at 14.3 volts after charging for 48 hours, your charger is COOKING them dead. There is no case where a charger should holding that high a voltage for that long. AGM's are especially vulnerable to overcharging, because they can not vent gas without damage, and you can not replace lost water.

If the charger is not set up correctly or has failed, new batteries will suffer the same fate.

Can you describe the variables you have programed into this charger for the charging profile?

[Pdemajo]

The Charger is a 40Ah Dolphin SM series. it has a particular setting for AGM which was properly set. It was also checked by a marine electrical engineer who found no fault in it, but i do understand your logic. When the batteries are fully charged and the charger is on they are reading 14.3V, and that is a fact.
Could it be that if the batteries are nearly dead and therefore do not hold their full capacity, the charger would continuously try to charge them?

[ItDepends]

Originally Posted by Pdemajo

The Charger is a 40Ah Dolphin SM series. it has a particular setting for AGM which was properly set. It was also checked by a marine electrical engineer who found no fault in it, but i do understand your logic. When the batteries are fully charged and the charger is on they are reading 14.3V, and that is a fact.
Could it be that if the batteries are nearly dead and therefore do not hold their full capacity, the charger would continuously try to charge them?

The charger has no "knowledge" of the charge state of the battery. All it knows is how many Amps it is outputting into how many volts.

There are a couple possibilities. When you stopped the charge cycle, did you notice if the charger was reporting it was in "bulk" "absorbtion" or "float"?

[Pdemajo]

Originally Posted by ItDepends

The charger has no "knowledge" of the charge state of the battery. All it knows is how many Amps it is outputting into how many volts.

There are a couple possibilities. When you stopped the charge cycle, did you notice if the charger was reporting it was in "bulk" "absorbtion" or "float"?

I just went to take a look. I only have one battery now. With the charger on, the victron was telling me that the batt was at 14.3V, but was putting only 2Ah...I then looked at the charger itself and both the power and the boost were on as in the picture attached...what do you think? is this on float since the Ah going in is only 2?
I also touched the battery to see if it was in any way hot - i was not.

[smac999]

Your 40a charger is too small for your 480ah agm house bank.

The agms will not like that. Nor will they like being held at 14.3v. At 2a charge (not 2ah…) it should be down to float at 13.5v.

Agms Likly want min .2c charge and up to maybe .4c . That puts you at 100- 200a charger.

And that means shore power or gen often to get those high amps into them.

[Pdemajo]

Originally Posted by smac999

Your 40a charger is too small for your 480ah agm house bank.

The agms will not like that. Nor will they like being held at 14.3v. At 2a charge (not 2ah…) it should be down to float at 13.5v.

Agms Likly want min .2c charge and up to maybe .4c . That puts you at 100- 200a charger.

And that means shore power or gen often to get those high amps into them.

Yes...that makes sense...thank you!!

[zstine]

If you are sure they are fully charged, then it sounds like it could be a dead cell.. That happened to me and I had similar results. Assuming you can access each cell like my Lead Acid batt's, get a cheap specific gravity hydrometer tester (~$10 amazon) and test each cell. If you have a bad cell, one will be dead, duh, while the others are not. The other possible cause is low water level, but if you have sealed AGMs than you can't add water.. and probably can't check for a dead cell. You'd have to isolate each battery and see if one is not fully charged compared to the others.
BTW, I believe I had a bad cell from new, but because I was initially doing weekends on the boat and had a fairly large bank, I didn't realize it until we moved onto the boat and the batteries we not performing well. By that time we were in the Caribbean and the special 12VDC golf cart 150AHr batteries couldn't be purchased until we made our way to PR.