Strange Electrical Problem

[ozsailer]

Have to agree with a lot of what has been stated already. While theoretically you can run your AGMs down to 50% is not recommended as a long term solution. As stated 12.1 is way down. You also don't state what your voltage is after you charge.
In my opinion while your voltage will give you some indication of charge it is not accurate by any means. By running your motor for only an hour to an hour and a half is just not going to get your batteries up to full charge.
I would highly recommend installing a battery monitor to give you a far more accurate picture of the charge state of your batteries. Have you actually sat down and worked out how much power you consume on a daily basis. Without knowing this it is impossible to work our your power needs and requirements.
450 watts of solar is on the light side for trying to charge such a large battery bank. You need a charging system relevant to your battery capacity. Rather than using your motor to charge I would think a small generator and good battery charger would be much more efficient and cheaper to run. You state you are power hogs, hmm without being rude maybe its time to assess your actual power needs and work within those limitations. In comparison I have 800 amp hour house battery and 1200 watts of solar and on cloudy days this just keeps us at 100 % after charging during the day.
I would highly recommend going to a marina and fully charge your system and install a battery monitor system and work within its capabilities. Talk to a marine expert and get their advice. It will save you money and stress in the long run.


Greg H
Lagoon 440

[Scott Berg]

Sounds to me like you may indeed be suffering from plate sulfation from a partial state of charge (PSOC) issue. IF you have Lifeline batteries you may be able to equalize them and that may help. See: https://lifelinebatteries.com/2015/1...agm-batteries/

Other brands behave differently. We recommend that those using AGM batteries for their house banks bring them to full charge at least once every two weeks. This usually is done by solar panels or long motoring with externally controlled alternators.

[NPCampbell]

If your batteries are suffering from sulfation due to prolonged use without a topping charge you may be able to partially reverse the sulfation and extend the life of your batteries.

If the sulfate hasn't hardened, there are a couple common remedies to salvage your batteries: Overcharging with low current and pulsation.

Overcharging can be done DIY if you are able to measure the specific gravity of your electrolyte. Basically, you apply a low current charge, ~2.6v/cell charge to a fully charged battery until the specific gravity of your electrolyte rises back to normal (1.26?). The increased SG indicates that the sulfate is dissolving back into the electrolyte. Regulating the charge current and voltage as well as battery temperature during this process is important.

I'm not sure how to measure the efficacy of the pulsate method and I'm not sure how the various pulsation products out there do either. There appear to be a lot of "snake oil" products out there so do your research if you go this route.

[sailinglegend]

Originally Posted by nhschneider

....What could have changed so the batteries will suddenly only accept about half of the charge they accepted last week?.....

I tend to agree that you have probably murdered your new AGMs by not charging them properly.

This could be because one of the 8 batteries has failed prematurely. check them all to see if one is getting hot and check the voltage of the bank with a small load after fully charging and left for about 20 minutes.

Best to disconnect 6 of them and leave for at least two hours and check the voltages of each individual 6v battery. If all are the same replace them and recharge fully and then check the other two.

If they are faulty then why have they failed in one year?

1. Not all AGMs are created equal - you can't afford to buy cheap because they won't last - especially on a boat if the batteries are really designed as a solar standby battery and not designed for regularly falling off three metre waves on a boat.

2. If you are using the main engine or a generator you will never get a large 896Ah bank to 100% fully charged without running them regularly for hours and hours and hours.

3. Your charging sources are probably falling to float much too early - this could be extend on the Balmar regulator but you need to monitor the charge current as it approaches the point of dropping to Float. This should be about 1.5%-2% of the battery capacity - that's around 15 amps not 50 amps!

4. Don't try and set it lower than this because you may overcharge the battery unless you are monitoring it. Overcharge the battery isn't too much current but it's too much voltage. A battery limits the current it will take but leaving it at 14.4v when it is fully charged will cause excessive gassing. This may not be too bad for flooded lead acid that can be topped up with distilled water, but sealed FLA and AGMs may suffer badly.

5. Let the solar finish the charging - but you need to make sure your panels can deliver enough Ah at a decent float voltage before the sun goes down. That is very difficult on most boats.

6. The final test for when you think the batteries are fully charged is to turn on the main engine or generator. This will kick the regulator into absorption mode and then you measure the current going into the batteries. This 'end amps' or 'return amps' figure should be about 0.5% of the battery capacity. That is about 5 amps for your bank, but it must be at the absorption voltage of about 14.4v.

So what AGMs do you have and do you have a battery monitor - if not go for the new Balmar SG-200. That will tell you your State of Health of the bank - i.e how much capacity have you lost.

[skipmac]

Originally Posted by NPCampbell

I'm not sure how to measure the efficacy of the pulsate method and I'm not sure how the various pulsation products out there do either. There appear to be a lot of "snake oil" products out there so do your research if you go this route.

A couple of forum members have tested pulsation and similar desulphating techniques and chargers and found no benefit at all. From all independent testing I've seen all of them are snake oil.

[NPCampbell]

Originally Posted by skipmac

A couple of forum members have tested pulsation and similar desulphating techniques and chargers and found no benefit at all. From all independent testing I've seen all of them are snake oil.

Without being able to reliably measure sulfation it makes it tough to do a valid comparison between products. Specific gravity and battery temperature are pretty important factors in recovering a battery and I know of no chargers that take these factors into account. This is what makes me critical of most claims.

However, there are some promising reviews of companies & products that have been around for a while:

Battery Desulfators - Fact or Fiction - Import Tuner Magazine

... but you can never be sure if they were taking kickbacks or not.

[sailorboy1]

Well ...................................

Don't go all panic depression mode yet. Go spend a day in a marina connected to shorepower and get a real good full battery charge, do a discharge and then do a full recharge again and see how the batteries respond. (you could do with generator and solar if they really can keep the voltage up and it doesn't make you crazy running the generator at such a low load). Made sure the voltage stays at absorption till at battery is down to at least no more than 0.5% and keep it then a few hours.

[skipmac]

Originally Posted by NPCampbell

Without being able to reliably measure sulfation it makes it tough to do a valid comparison between products. Specific gravity and battery temperature are pretty important factors in recovering a battery and I know of no chargers that take these factors into account. This is what makes me critical of most claims.

However, there are some promising reviews of companies & products that have been around for a while:

Battery Desulfators - Fact or Fiction - Import Tuner Magazine

... but you can never be sure if they were taking kickbacks or not.

Forum members Maine Sail and BTrayfors, both extremely knowledgeable in marine electric and electronics both did extensive testing on pulsating chargers and some variations. Their test results were based on testing capacity before and after the test and both found no improvement in amp hour capacity after repeated tests. Neither had anything to gain from the tests.

Maine Sail has been known to take stuff apart to see what's going on inside but can't recall if he did that with any of the test batteries. I do know that he is a member of the ABYC and I believe does testing and helps write the standards. Regardless I know he has some very expensive and sophisticated test equipment so I would take his results as the gospel truth.

[skipmac]

Copy of comments from Maine Sail in a previous discussion on battery pulsating desulfating chargers.


I have been testing these sorts of "desulfator" devices now on and off for about 7 years. Not a single one of them has actually "desulfated" a battery or returned any quantifiable increase in Ah capacity. I keep hoping they will....

I currently have a BLS (Battery Life Saver) running on a less than two year old Lifeline AGM and in nearly 2.5 months it has done absolutely squat. The sister battery it was in parallel with improved by about 4% after 8 hours of equalization voltage and the BLS battery has had no change after 2.5 months...

I am quantifying my results with internal impedance baselines and then monitoring for changes. I am also running 20 hour capacity tests for baseline and then 1 each month looking for improvements.. I am also high amp load testing as well.

Maybe this one is different but it really looks like the same marketing as Pulse Tech or BLS or any of the other desulfator companies.

[Stu Jackson]

AGM Batteries - Making The Choice (from Maine Sail)

https://forums.sailboatowners.com/in...choice.124973/

AGM Battery Issues and the Blue Seas Dual Circuit Switch (from Maine Sail) "DARN AGM Batteries"
https://forums.sailboatowners.com/in...teries.133773/

Additional Observations on the Limits of AGMs Electrical Systems 101


You may have been undercharging them.