AGM batteries persisting at low voltage

[Paul L]

Originally Posted by a64pilot

Then you kill the other battery overnight.

Kill is a little strong. The house can be partially charged by the main engine for a few days while yoh equalize the other batt. Its not like the OP has a lot of options anchored out in the Marquesas.

[Mike Banks]

I used to change my batteries at two years. 400 watts of solar is an adequate charge power to run everything except hot water and stove. Assuming your batteries are fine for the moment, turn off the fridge at night and see what your ammeters are showing, then turn it on again and see any difference, then subtract from that difference in current the draw the fridge SHOULD be taking if working to specs, (Watts divided by volts) any extra current drain means the fridge is faulty.

At night, get a torch and turn off items on your switch board one at a time noting the change in current each time. You know what equipment is on each of the fuses at each switch, or should be, so any changes in current draw could be suspect.

Once you have isolated the overloaded system, the rest is easy. In my case it was a bilge pump.

[basssears]

Originally Posted by Marathon1150

Since then, unless there is power going into the batteries (engine, solar, wind) they are hovering at 11.8 or 11.9 overnight.

Good thoughts in other posts, my one clarification would be to make sure you're checking your battery voltage at rest with no loads and no inputs. A properly fully charged battery will easily read below 12v if it has a big load on it (i.e. is the "new to you" fridge compressor pulling lots of amps?).


To truly get the voltage of your batteries I would unhook them, let them sit for 1/2 hour or so, then read the voltage. Anything less than that (i.e. just turning everything "off") could lead you down a false road if there are sneaker circuits somewhere that put a load on you don't know about.



You probably already know this but in case you don't...

[Marathon1150]

Many thanks for the additional comments and advice. Here is an update. We measured voltage at the batteries over a period of one hour after disconnecting them from all but the BEP and some other LED indicators. Voltage at the batteries is 0.2V higher than at the BEP monitor. Over a 2 day period characterized by bright sun/intermittent or no clouds, battery voltage went up. We also ran the engine for each of these days until the regulator started to reduce power going into the batteries (about one hour on each day). Voltage one hour after shutting down the engine and when sunlight was negligible was about 12.7 on each day. Voltage dropped to 12.4 overnight with the fridge on, in each case. Voltage at the batteries read the same as in the Balmar regulator and averages about 0.2V higher than at the BEP monitor. We think we will be ok to get to Papeete starting tomorrow and have a spot arranged in a marina there. Once we sort out how to connect the charger to shorepower (Xantrex 40 Amp and will accept 110 to 220V) we will fully charge the batteries and then do the Lifeline recommended “conditioning” charge. Hopefully the batteries can be salvaged. Many thanks again for the terrific and helpful comments and pointers.

[basssears]

Without knowing all the variables this to me sounds relatively normal, so hopefully that means your batteries are recovering and will continue to serve you.

[belizesailor]

Originally Posted by NYSail

You can equalize your lifelines....... call them up and they will tell you the voltage...... think it’s 15.5 but double check with them. if during your passage you never brought them back up to full charge you may have over taxed them..... equalizing them may help save them.

Greg

This^^.

Ive found regular equalization of my Lifeline AGMs makes a noticeable difference in performance.

A few months after installing them mine had similar symptoms. I thought: oh crap, Ive murdered them. Went back to dock, equalized them, and they bounced right back.

[a64pilot]

Once equalized though you need to determine if and why there were being undercharged to begin with.
I have found that to be sure I get to a full charge each day, I need to run a generator for a half hour to an hour each morning when the bank can accept all the generator can make.
Of course by noon, we have excess Solar and that is the time to turn on the inverter and make ice, wash clothes, watch TV or otherwise use the excess Solar, cause by then the output of the panels is high, but the banks acceptance rate is low.
However it takes four or more hours being at absorption voltage for my bank to slowly come down to 3 amps acceptance, then it’s fully charged.

IF you get to 100% fully charged every day, then there is no real need to equalize.

If you can determine your banks state of health by either the new Smart Gauge or the old one and am amp counter, then you can use that to determine that you need to equalize, or get into the habit of every morning watching the banks voltage, it should be the same every morning, if it starts slowly decreasing, then you need to fully charge, and equalize.

However the goal is to be fully, 100% charged as often as is possible, by whatever means necessary. If your going to burn fuel to do that, it’s best to do it first thing in the morning when the bank will accept 100 amps charge or more, not late in the afternoon, when it will only accept 4 or 5 amps.

[Suijin]

Originally Posted by NYSail

You can equalize your lifelines....... call them up and they will tell you the voltage...... think it’s 15.5 but double check with them. if during your passage you never brought them back up to full charge you may have over taxed them..... equalizing them may help save them.

Greg

I really doubt that it is an issue associated with reduced charge capacity from not getting to a full charge in even a month. My Lifelines were older and I routinely went weeks without bringing them to a full charge. The decrease in capacity is incremental and nothing near what the OP is experiencing, and his are only two years old.

I would put money on the fridge controller. To the OP, is the fridge running more than normal? Have you turned it off/disconnected it entirely, or measured it's load? I turn mine off routinely at night but mine holds the cold pretty well and is only up 3-4 degrees in the morning.

[sailinglegend]

Originally Posted by Marathon1150

.......Once we sort out how to connect the charger to shorepower (Xantrex 40 Amp and will accept 110 to 220V) we will fully charge the batteries and then do the Lifeline recommended “conditioning” charge.....

This is just one of your problems - your 40 Amp charger - with 420Ah of Lifelines you should have a 100 amp charger. Their manual says a charge current of 20% of the Ah capacity is the minimum needed - that is 84 amps - and then an overhead is needed to power boat loads at the same time as charging.

You can't just change your batteries from FLAs to AGMs without re-thinking your charging system.

[Exile]

Originally Posted by sailinglegend

This is just one of your problems - your 40 Amp charger - with 420Ah of Lifelines you should have a 100 amp charger. Their manual says a charge current of 20% of the Ah capacity is the minimum needed - that is 84 amps - and then an overhead is needed to power boat loads at the same time as charging.

You can't just change your batteries from FLAs to AGMs without re-thinking your charging system.

I'm not sure this is how all chargers work, but my 9-year old Xantrex XC5012 (no longer mfg. I think) monitors each of my 3 Lifeline 8D's and then applies the appropriate charge to each battery separately. So it's my understanding (could be wrong) that what I effectively have is a 50A charger applying all of its charging capacity to each of my 255ah batteries at any one time. That's about the required minimum 20% you cite per the manual.

Not sure if newer model Xantrex chargers work the same way, but something the OP may want to look into. Unless my understanding is incorrect . . . .

[sailinglegend]

Originally Posted by Exile

....So it's my understanding (could be wrong) that what I effectively have is a 50A charger applying all of its charging capacity to each of my 255ah batteries at any one time....

I'm surprised you don't even know how your 50 amp battery charger works.

50 amps is the maximum that it can deliver - not 50 amps to each battery at the same time - that would make it a much bigger and much more expensive 150 amp charger.

Everyone on here please RTFM before you post to avoid confusions like this!!!!

Why do posters expect others here to correct their basic misunderstandings.


My signature for when I get annoyed.
Ignorance isn't what you don't know it's what you think you know that is incorrect.

[Exile]

Originally Posted by sailinglegend

I'm surprised you don't even know how your 50 amp battery charger works.

50 amps is the maximum that it can deliver - not 50 amps to each battery at the same time - that would make it a much bigger and much more expensive 150 amp charger.

Everyone on here please RTFM before you post to avoid confusions like this!!!!

Why do posters expect others here to correct their basic misunderstandings.


My signature for when I get annoyed.
Ignorance isn't what you don't know it's what you think you know that is incorrect.

No, no, you misunderstood my post and left out the pertinent part:

"[My Xantrex XC5012] applies the appropriate charge to each battery separately. So it's my understanding (could be wrong) that what I effectively have is a 50A charger applying all of its charging capacity to each of my 255ah batteries at any one time."

So it's not acting as a 150A charger by applying a 50A charge to all 3 batteries at the same time, but selecting which of the 3 batteries is most in need of charging and applying the appropriate charge to each one separately.

I'll double-check my charger's manual on this & post what it says. We're all just trying to learn here while hopefully helping out the OP. No need to get annoyed.

[a64pilot]

Your charger will only charge each battery independently, if they are in fact independent and are not connected electrically. If they are say connected in Parallel, then what you have is one big battery and the charger cannot differentiate between them.
Doesn’t hurt to have them each connected to the charger though, so I’d not change that.

You can charge a larger Lifeline bank with a small charger, it’s not optimum but it works.
If it didn’t, then all of us that depend primarily on Solar would have to have truly massive Arrays to meet the recommended spec.

[sailorboy1]

Originally Posted by Marathon1150

Voltage one hour after shutting down the engine and when sunlight was negligible was about 12.7 on each day. Voltage dropped to 12.4 overnight with the fridge on, in each case.

sound like normal numbers to me with my 440AH house bank

[belizesailor]

Originally Posted by Marathon1150

Many thanks to all for the helpful and well considered advice. Much appreciated! We will not have access to shore power for another 10 days or so thus we will need to use the solar panels to try and equalize the batteries. The Blueskies solar controller, I believe, can be set up to do this. There are certainly some important lessons learned coming out of this experience. Many thanks again to all.

I have a BlueSky 3000i and yes it can be set up to equalize. It can be set up for manual or automatic. I dont like the idea of unsupervised automatic so mine is set for manual.

Once configured, get batteries to a full, or very nearly full, charge then initiate equalization. I turn off all breakers first so I dont fry anything with the higher voltage (good time to defrost the fridge). Its all automatic after initiated.

My configuration will get batteries to float, even with full normal load, on a good solar day, so its easy for me.