Strange Electrical Problem

[nhschneider]

We have been cruising for eight years and have a pretty good grasp of our electrical system. We installed eight new 224-amp 6-volt AGM batteries slightly over a year ago and they have been great. To charge the batteries, we have two 225-watt solar panels and a single-cylinder Kubota diesel with a 150-amp Leece-Neville 12-volt alternator which is regulated by a Balmar MC-614 external regulator. I’m embarrassed to admit it but we’re power hogs. We draw a lot of amps out of our batteries and have to put a lot back in.

I usually wait until I see 12.1 or less volts in the battery bank before I start the single-cylinder Kubota and I’ll initially see about 135 amps going into the batteries but it will taper down to about 100 amps pretty quickly. Once the batteries are only accepting about 50 amps, which takes about 90-120 minutes, I shut the engine down.

However, just recently I’ll only see a maximum of 70 amps going in on start up and then it quickly tapers down to about 40 amps. Granted, we’re mostly out of the tropics (24°N) and the demand from the refrigerator and freezer are less but that shouldn’t affect the charge rate. My first suspicion was a problem with either the alternator or the regulator so I tried charging with the main engine.

About ten years ago, I installed a 90hp Beta Marine with two Iskra alternators - a 100-amp (which we only use to charge the starting battery) and an internally-regulated 150-amp alternator to charge the house battery bank. It’s been a great, trouble-free system but you can imagine my surprise when I started the Beta Marine and got the exact same charging issues that I have with the single-cylinder Kubota.

Since the output of all three charging sources (solar, single-cylinder Kubota and the Beta Marine) terminate on one side of a 300-amp ‘T’ fuse, I suspected that the fuse could have developed some sort of internal resistance so I replaced it with a new spare I had on hand. No change.

I keep the serpentine belts tightened to factory specs which is 12mm of deflection when 8 kilos of force are applied at mid-span - it feels banjo string-tight to me but I haven’t had any belt or bearing failures and the Beta Marine has almost 5,000 hours on it.

Of course, I’ve checked, cleaned and tightened all the connections. Everything electrical that I assemble gets generously coated with Lanocoat grease and I think that has helped keep everything so trouble-free.

Thank you for reading this far. I know it’s complicated. What could have changed so the batteries will suddenly only accept about half of the charge they accepted last week? Or, why are two different alternators suddenly only putting out half the amps they were outputting last week? If you have any ideas or suggestions, I’d like to hear them.

Fair winds and calm seas.

[Farmer9009]

Just a thought but have you confirmed the device or gauge you are using to measure with is reading your amps correctly?

[RonRicco]

My guess would be that the capacity is much lower because of how far (and often) they have been discharged. Since they have lost the capacity, the input tapers off much faster. 12.1v is a pretty low voltage.

I will hang up now and wait for the experts to chime in.

[disputin]

Not an expert, but I'm getting ready to convert from Lead Acid to AGM and I found this discussion by someone with the moniker Maine Sail insightful.

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

Sean

[smac999]

Do you ever get them to 100%? Sounds not which is murdering your AGms.

Fireflys would help you due to you never fully charging.


You can test the charging by putting a huge load on the battery. Ie if you have an inverter. Put a hairdryer or 1500w heater on. If you are drawing 150a from the batt the alt should put out 150a even if the batteries suck. If the charging now fully works. The batteries are the issue. If it still only puts out 70a. You have other issues.

[nhschneider]

Originally Posted by Farmer9009

Just a thought but have you confirmed the device or gauge you are using to measure with is reading your amps correctly?

I have a Xantrex Link-Pro installed but the single-cylinder Kubota also has an amp gauge. They both seem to show the same about number of amps going in.

[nhschneider]

Originally Posted by RonRicco

My guess would be that the capacity is much lower because of how far (and often) they have been discharged. Since they have lost the capacity, the input tapers off much faster. 12.1v is a pretty low voltage.

I will hang up now and wait for the experts to chime in.

Correct me if I’m wrong but if I discharge to 12.1 volts, that’s barely a 50% discharge. These batteries should be able to endure at least a 1,000 discharges that are no more than 50%, shouldn’t they? They’ve probably had around 400.

I’m not trying to be argumentative. If there are flaws in my thinking, please let me know.

[nhschneider]

Originally Posted by smac999

Do you ever get them to 100%? Sounds not which is murdering your AGms.

Fireflys would help you due to you never fully charging.


You can test the charging by putting a huge load on the battery. Ie if you have an inverter. Put a hairdryer or 1500w heater on. If you are drawing 150a from the batt the alt should put out 150a even if the batteries suck. If the charging now fully works. The batteries are the issue. If it still only puts out 70a. You have other issues.

Actually, on our passage from Panama to Mexico we had to motor almost the entire way so the batteries did get fully charged then. Just recently, we had to motor almost the entire way from Isla Socorro to Bahia Los Frailes, a distance of almost 300 miles and the batteries showed that they were fully charged then, too.

I like your suggestion for putting a big load on the batteries while charging. I’ll give that a try.

[Sojourner]

I don't know much about batteries yet unfortunately, but I do know the specs for my batteries (AGM) and victron/sterling chargers call for something like 55 amps charging rate, not more, which is where they're set. Don't know if that's an issue or not for you...

[sailormed]

"I usually wait until I see 12.1 or less volts in the battery bank before I start the single-cylinder Kubota.......". Is this after the batteries have been without load for a certain. time?
The battery charge % based upon voltage is after a period of no charge to let the batteries recover. Officially 24 hours I think, but after 1 hour you already get a good approximation.

[Simi 60]

Showing fully charged does not necessarily mean they are.
Our batts usually show fully charged (100% and 0 ah used) by 11am but the solar panels are still pushing tapered off amps into those batteries until the sun disappears.

[GordMay]

Greetings and welcome aboard the CF, Sean.


12.1V represents a state of charge of about 50%, the maximum level to which you want to discharge.
If the batteries are accepting 50 Amps, they are nowhere near fully charged.

[Sailmonkey]

Originally Posted by GordMay

Greetings and welcome aboard the CF, Sean.


12.1V represents a state of charge of about 50%, the maximum level to which you want to discharge.
If the batteries are accepting 50 Amps, they are nowhere near fully charged.

Agreed

12.1 is pretty depleted, you have 896 ah of batteries.

Running the generator to replace the 448 ah of consumed power should take minimum (it will be much longer) 4-5 hours. Reality is that 100% will take 6-10 hours of charging. 50 amps going into the batteries is them still charging, not them charged.

I hate to say it, but you’ve murdered you agm batteries by never fully charging them.

[Ostinato]

I’ve had a similar issue but it is isolated to one charging source. I’m still trouble shooting it but at this point I pretty sure it is wiring. (One engine/alternator produces high amps, the second set significantly lower but both have separate cables running to the same battery bank and switched out alternators). I am going to try looking for resistance using an ohm meter next. Let us know what you find.

BTW AGMs are not usually considered the best for deep cycling. You need to read the lit from companies that sell several types to get more truthful info. Hope it is not that.

[jkimbu]

Agree with smac and others... if that bank is still accepting 50A when you turn off the genset, you're still in bulk charging stage and haven't fully recharged in a long while!

The good news is you probably don't need a new genset or alternators.