Battery problem thoughts much appreciated!

[smac999]

It's possible you have one bad battery that is droping the whole bank down. Likly you need to test all 6 individually. Otherwise sounds like they are all bad now. 30a load is not much on a 600ah agm bank.

You should not be droping below 12v though. The fact that you are allowing your battery drop to 11.6 means you don't understand what's going on. You should have started charging long before you see that. At 11.6v you're down ariund 40%

So either the ah meter is set for wrong capacity. Or you batteries are now less then half its rated capacity. (Drew 25% of rated out and that took them down by 60%)

[misfits]

You can't use voltage to determine SOC if you're drawing off the bank.
At 11.6 volts, you're at 75% discharge, SOC would be around 25%.
Sounds like the batteries are toast for whatever reason.

[Scrimshaw4]

Once your system reaches float I'd recommend that you disconnect each battery, let them rest for a little bit to relax the surface charge and then individually load test them. This will indicate if there is a bad cell. Also, when was the last time you "shook" / "equalized" your batteries? AGM's can be restored like wet cells through this process. JMHO

[ZULU40]

Originally Posted by a64pilot

Either as posted they are cooked.
Or I’m betting they are not fully charged, only charger I have ever found that will really fully charge a bank is my Magnum inverter charger with the BMK kit installed, the BMK is a battery monitor and of course knows the exact amps going into or from the bank, it can be used to tell the charger to drop into float when the correct charge rate is reached, for my 660 AH bank, that is 3.3 amps, prior to having the BMK, I would have to recycle either of my chargers to get to a full charge, several times as both would drop into float prematurely.
This starts a gradual walk down in charge, if you only charge to 95% each charge cycle, the total charge walks down each cycle, so pretty soon your not well charged at all, and you think you are.

30 amps for a big IP like this isn’t excessive, as it may be that he is running a big inverter and a TV or two, and maybe a fridge and freezer.
If we are watching TV, and have both my fridge and the Engle running, I’m at 25+ amps or so myself.

The key to me that is telling me your bank is discharged is that voltage recovers on the charger, it’s that or a loose battery connection, either would show the same result.

I think this is right
AGM swallow a greater charge than older chargers are used to, some even capable of

[john61ct]

I have not read the whole thread, but it seems obvious the system was installed by overpaid idiots.

IMO the whole system needs a detailed audit over time by someone who actually knows what s/he's doing using accurate DMM and ammeters at the key circuit points.

This competent person should be paid to not only fix the problems, but educate you the OP so you yourself know what your gear is supposed to be doing,and how to use those tools to ensure they are operating properly.

Do not rely on "professionals", become an expert yourself.

[john61ct]

Are we really certain that Roll's forays into the AGM market live up to the stellar reputation of their traditional FLA lines?

They are produced by an OEM in China rather than in Rolls' own NA factory, my understanding is by FullRiver. Doesn't inherently mean good or bad, lots of variables at play there.

Just that it takes a very long period for the market's collective wisdom to be able to say they're as robust and long-lasting as Lifeline, Odyssey or Northstar.

And I'm not saying this question relates to the OP at a causal level. But it certainly is relevant to whether or not the bank will need replacing if they've been PSOC abused so badly for a full year.

I also have the same question about Trojan's AGM.

[roland stockham]

My guess is you have a problem with measuring the voltage. Get a multimeter and check the voltage at the battery terminals. It should either be about 13.4v with batteries fully charger and little power going out (charger is in float mode) or 14 -14.8 with batteries better than 75% charged but not full and the charger in recharge mode. I would not be suprised to find the shunt if fitted after the rotary switch.

The other thing I would check is the 3 way rotary switch. These are notorious failure points, Ideally bin it and get something better. Boat builder love to fit them as they are cheap and simple but they really have no place on a cruising boat. Power levels are to high and they regularly fail. They also present a significant fire risk because as they fail they create high resistance and start generating heat.

Should be replace with either a 0v drop splitter or a diode block and smart regulator

If this does not sort it have a look at the overall wiring. Has a lot of high power equipment been added? It could be that your core circuits are not heavy enough for all the additions or that you have significant corrosion.

[Robert Tilbury]

WOW 30 Amps ,, i only draw 7.8 amps with the engla fridge running , AIS and depth sounder (as anchore watch on ) and a few LED lights (cabin rear deck and anchore ) ,
What would be pulling 30 AMPS ?
My HF at 100 watts Transmit only pulls 19 amps ??


best get a sparky to check that out

Let us know how you go some thing sounds real wrong ,

By any chance is your alternator on your motor warm ?
Maybe a diode leaking ?

[roland stockham]

30A is not that high, my kettle draws 75A, big power tools and vacuum are in the 20-30A range but it is probably going to be via the inverter. All short term so the amp hours used are low.
Highest dc loads are bilge pumps and autopilot, both can draw up to 18A.

[a64pilot]

Originally Posted by misfits

You can't use voltage to determine SOC if you're drawing off the bank.
At 11.6 volts, you're at 75% discharge, SOC would be around 25%.
Sounds like the batteries are toast for whatever reason.

Some batteries you can, Lifeline in their manual has a chart for SOC for batteries when under a 20 hour to 50% discharge load, and an 8 hour to 50% load. The numbers are very close to being the same.
Never have understood what a SOC chart that requires the batteries to be under zero load for hours is good for, what cruising boat disconnects their banks for hours, regularly?

[Paul L]

Originally Posted by john61ct

Are we really certain that Roll's forays into the AGM market live up to the stellar reputation of their traditional FLA lines?

.......

We obviously aren't. I am. My Rolls AGM have had excellent service and are still going strong. Far superior to the previous Northstar poor quality product.

[roland stockham]

A word of warning - you cannot equalize any sealed lead acid battery without damaging it.
With 6 small AGM's even a very small charging error could wreck batteries in a year. These are going to be fragile particularly if overcharged and not recoverable. Run in parallel means that if one battery fails it will prevent the others from charging and fairly quickly wreck all of them.
Unless you are stuck with this system because of space You would be better with bigger 6v cells which are much more robust.
AGM's can be good if you leave the boat for long periods without charging as they have low self discharge rates but they are much more fragile due to the very low water content. Even a small overcharge will write them off. The 'high charge acceptance' is a bit of a myth. Yes they will take a higher charge at 50% SOG but because you have to limit max voltage the total charge time to 100% is actually greater. This does not matter if the boat is only used at weekends or less. Expected life for AGM is half FLA's and the cost is about double making them 4x as expensive for very little gain.

[kenbo]

Originally Posted by roland stockham

A word of warning - you cannot equalize any sealed lead acid battery without damaging it.
With 6 small AGM's even a very small charging error could wreck batteries in a year. These are going to be fragile particularly if overcharged and not recoverable. Run in parallel means that if one battery fails it will prevent the others from charging and fairly quickly wreck all of them.
Unless you are stuck with this system because of space You would be better with bigger 6v cells which are much more robust.
AGM's can be good if you leave the boat for long periods without charging as they have low self discharge rates but they are much more fragile due to the very low water content. Even a small overcharge will write them off. The 'high charge acceptance' is a bit of a myth. Yes they will take a higher charge at 50% SOG but because you have to limit max voltage the total charge time to 100% is actually greater. This does not matter if the boat is only used at weekends or less. Expected life for AGM is half FLA's and the cost is about double making them 4x as expensive for very little gain.

You can and should equalize Lifeline AGM's

[kenbo]

And Deka (East Penn Manufacturing) recommend equalizing both their AGM and Gel batteries albeit at a much lower voltage than their flooded counterparts.

I've been thinking about the OP's issue and I may have an idea as to what the problem maybe. The OP states he went from Lifeline to Rolls AGM's about a year ago and were installed by a third party. Perhaps the installer thought ah, AGM's for AGM's no need to change any charge settings. Lifeline has an absorption of 14.3v vs. 14.7v for the Rolls. Not a really big deal but over time the Rolls would loose capacity due to never being fully charged.

Just a thought.

[kenbo]

Originally Posted by smac999

It's possible you have one bad battery that is droping the whole bank down. Likly you need to test all 6 individually. Otherwise sounds like they are all bad now. 30a load is not much on a 600ah agm bank.

You should not be droping below 12v though. The fact that you are allowing your battery drop to 11.6 means you don't understand what's going on. You should have started charging long before you see that. At 11.6v you're down ariund 40%

So either the ah meter is set for wrong capacity. Or you batteries are now less then half its rated capacity. (Drew 25% of rated out and that took them down by 60%)

Exactly, one bad cell can kill the other 35 in short order an the symptoms would be just what the OP is experiencing.