AGM Battery Sudden Drop

[Snore]

I need to check in with the CF Brain Trust for some help.

After having issues with my house batteries I installed a SmartGauge. Pending retirement (this year?) the boat is used mostly for day-sailing and some short trips.

Here are the facts of what happened:

• Numerous Day trips with light electrical use an 50 watt Renogy cell through an archaic controller. No real drop in reported SOC. Lowest reported was SOC. Load was Garmin 440, Ray depth and knot log, Madman WiFi adapter, SH VHF/AIS receiver.
• Decided to stress the house bank yesterday. Ran the refrigeration unit, as well as the usual load and the solar cell.
• Frequent checks of the SmartGauge (SG) indicated the usual, slow drop in SOC and last noted SOC was the usual 92%.
• Went to use the head and saw a low voltage warning on the SG.
• Immediately, flipped to starter battery and brought the engine on-line.
• The refrigeration was taken off line.
• With the engine on-line, I briefly flipped to the house bank and for 3-4 minutes let the batteries charge.
• While charging the house batteries was prudent from a readiness standpoint, it did little to help analyze the problem.
• With the battery no longer being charged for the next 90 minutes I took voltage and SOC readings off the SG. The readings are confusing:
  • 12:45 SOC 1 13.2 VDC
  • 13:10 SOC 5 12.9 VDC
  • 15:11 SOC 14 11.9 VDC (back at dock)

Just for "giggles" when I headed back to the dock, I used the house battery to fire up the engine. Based on ear, it seemed to crank at a normal RPM.

To save the obvious questions-

• No apparent intermittent battery drains.
• No amp meter on-line, a Victron is on board and being wired this week.
• AGM are guessed to be 5 years old.
• There is a house charger that tops off and trickle charges the batteries.
• SG has been in use for about 6 weeks.

Since both the inverter and refrigeration are wired directly to the house bank (with fuses), they are candidates for somehow creating a drain.

But before I go chasing low probability issues, are these symptoms consistent with an AGM battery dying?

Also the SOC readings on the SmartGauge are inconsistent with the voltages. Any thoughts?

Thanks for the anticipated assist.

[ShaktisBoy]

1. How big is your battery bank?
2. When was your last equalization charge?
3. Have you tried turning on the loads 1 at a time and measuring the rate of change?
4. Are all connections clean and tight?


You also mentioned that after you started the main engine to charge and then switched over to charge your house bank. On my vessels this is a big no no and can ruin your altenators.


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[Snore]

ShaktisBoy thanks

Originally Posted by ShaktisBoy

1. How big is your battery bank? two 34's
2. When was your last equalization charge? too long. I need to read up on doing this to seal batteries.... But read on.
3. Have you tried turning on the loads 1 at a time and measuring the rate of change? Right now I don't have a good amp meter. Taking a page from Mainsail, I have both a SmartGauge and a Victron. I just need to make the time to wire in the Victron. This project just got moved up the list.
4. Are all connections clean and tight? So I read this comment this morning and immediately gave it a pfft. Stopped by the boat and all the connections looked clean and tight. I the did the time-honored "wiggle test" and found that the positive lead on the house bank to the SG was not tight. When I wiggled it I got a low battery alarm. VIOLA! I think I found the culprit. The plan is to repeat the same series of events to see if there is a different result. Ideally with a working amp meter.


You also mentioned that after you started the main engine to charge and then switched over to charge your house bank. On my vessels this is a big no no and can ruin your altenators.

Okay, it looks like I screwed up. Assuming no on board generator-- What is the correct method to bring back a low bank?

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Thanks again for the assist!

[barnakiel]

Originally Posted by ShaktisBoy

2. When was your last equalization charge?

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Do we normally equalize AGM batts?

b.

[NewMoon]

Originally Posted by ShaktisBoy

You also mentioned that after you started the main engine to charge and then switched over to charge your house bank. On my vessels this is a big no no and can ruin your altenators.

FWIW
Unless you switch through OFF, switching between banks with engine running should be no problem. Batt switches are generally "make before break", such that going between Bank 1, Bank 2, and BOTH, is fine.

[Snore]

As always CF came through!

Thanks for all the inputs.

[DeepFrz]

Originally posted by Snore: 4. Are all connections clean and tight? So I read this comment this morning and immediately gave it a pfft. Stopped by the boat and all the connections looked clean and tight. I the did the time-honored "wiggle test" and found that the positive lead on the house bank to the SG was not tight. When I wiggled it I got a low battery alarm. VIOLA! I think I found the culprit.

It so often seems to be the things that we know are okay that bite us. So many times in my life I have struggled with something but the answer came to me while relaxing with a coffee, having a crap or lying in bed rather than when I was actively working on the problem. The old right brain/left brain thing I guess.

[Adelie]

Originally Posted by Snore

I need to check in with the CF Brain Trust for some help.

After having issues with my house batteries I installed a SmartGauge. Pending retirement (this year?) the boat is used mostly for day-sailing and some short trips.

Here are the facts of what happened:

• Numerous Day trips with light electrical use an 50 watt Renogy cell through an archaic controller. No real drop in reported SOC. Lowest reported was SOC. Load was Garmin 440, Ray depth and knot log, Madman WiFi adapter, SH VHF/AIS receiver.
• Decided to stress the house bank yesterday. Ran the refrigeration unit, as well as the usual load and the solar cell.
• Frequent checks of the SmartGauge (SG) indicated the usual, slow drop in SOC and last noted SOC was the usual 92%.
• Went to use the head and saw a low voltage warning on the SG.
• Immediately, flipped to starter battery and brought the engine on-line.
• The refrigeration was taken off line.
• With the engine on-line, I briefly flipped to the house bank and for 3-4 minutes let the batteries charge.
• While charging the house batteries was prudent from a readiness standpoint, it did little to help analyze the problem.
• With the battery no longer being charged for the next 90 minutes I took voltage and SOC readings off the SG. The readings are confusing:
  • 12:45 SOC 1 13.2 VDC
  • 13:10 SOC 5 12.9 VDC
  • 15:11 SOC 14 11.9 VDC (back at dock)

Just for "giggles" when I headed back to the dock, I used the house battery to fire up the engine. Based on ear, it seemed to crank at a normal RPM.

To save the obvious questions-

• No apparent intermittent battery drains.
• No amp meter on-line, a Victron is on board and being wired this week.
• AGM are guessed to be 5 years old.
• There is a house charger that tops off and trickle charges the batteries.
• SG has been in use for about 6 weeks.

Since both the inverter and refrigeration are wired directly to the house bank (with fuses), they are candidates for somehow creating a drain.

But before I go chasing low probability issues, are these symptoms consistent with an AGM battery dying?

Also the SOC readings on the SmartGauge are inconsistent with the voltages. Any thoughts?

Thanks for the anticipated assist.

If you want a very good discussion about whether or not to get AGMs and how to treat them read this: AGM Batteries - Making The Choice - SailboatOwners.com

[ShaktisBoy]

Originally Posted by barnakiel

Do we normally equalize AGM batts?

b.

If you are experiencing a loss of capacity I would equalize. My lifeline AGM have just gone through their first equalization since new about a year ago. The difference in the time between needing to charge is remarkable.

As far as switching from start batteries to house bank while the engine is running on my boats at least my manual says no. When I have run my house to low in the past I have selected both on the switch and been able to charge enough to get the bank back up to the point I could switch back over to the house bank alone. I also have been able to turn off all DC for a bit while the solar panel does its thing.


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[hellosailor]

Snore-
Equalizing AGMs is expressly forbidden by pretty much everyone except LifeLine/Concorde. It will cook or blow up others.
Switching batteries while the alternator is running, generally also a very bad idea. On some setups you can do it safely, but in general? If you survived this one, don't risk it again.


I'd run the engine and check the alternator output voltage to make sure it IS ok and charging. Then shut down, and either load test the batteries in isolation, or take at least a couple of them to a battery distributor and ask for a load test. That will tell you whether the batteries are good (although even one bad one in a bank could cause screwy results for the bank) and if they are, then you look to the rest of the system to see if something else is screwed up.
"Divide and Conquer". Sometimes it is the fastest solution, and it is always a certain solution.
The manufacturing date will be stamped or embossed on each battery. If it isn't on the top, look for a date code cleverly hidden by the label on the side of the battery, usually within an inch of the top. If it is really a clever code, a call to the manufacturer (or distributor) can get that cleared up.


You can get 8 years out of AGMs, but 5 years might be more normal lifespan for "casual not methodical" charging and use. So...check 'em, because lead ain't cheap these days.

[WolfgangSeaLife]

After reading all your experiences I probably did everything wrong. And I think, everybody else on a sailboat does too. So what can we do?

Here is what happened.
My question: Before going out to the islands for 6 months, should I buy new batteries?
I have 4 Deka, 3 years old, previously 4 Lifeline, each lasted 4 years.
Both 1100 CCA at 0 F or 1595 at 68 F, with 210 Ah each. That should total 840 Ah. When sailing I use 120 Ah a day, so I figured to 50 % I could sail for 3 days without recharging.
After 6 hours of sailing Voltage from previously 100 % charged batteries is 12 V, ready to drop further, so I have to charge, using engine or generator.

Alternator is 100 A MaxCharge Balmar and generator (or shorepower) through the charger/inverter Xantrex Freedom 25 also 100 A.

But the charging Amps drop 95 A for 15 min, 85, etc. After 1 hour 35 A. From here it can take hours, so I stop charging and charge again when at 12 V after 4 to 6 hours.

According to you experts, I should be charging at least at 20% of 840 Ah, with 168 A, but in average I charge with 50 A (35 to 95). And I don't charge to 100 % unless at shore power or running under engine for a whole day.
When at the mooring for 4 months, someone runs the generator for 1/2 hour every 2 weeks. Again, never fully charging.
Now at a dock, I charge full every two weeks.

But this happened at the dock: A bilge pump ran for a week due to some debris. The batteries dropped to 9 V, the Ah were -546. (Not bad after 3 years, however, those Ah were not really usable when getting below 12 V).

I charged to "full" with shore power through my Xantrex inverter/charger.
I cleaned the bilge pump, but it turned on again, and after 2 weeks, even the batter monitor display showed nothing, the batteries were dead.
I charged again with shore power. After a day to full charge to 13.4 V the charge monitor said "synchronizing" when I stopped. (I did not know that Deka batteries do no equalize as my previous Lifeline).

That's the situation.
Should I buy new batteries?
Is the AGM really the right battery for me on a sailboat?
What should I do differently when charging? Run the engine or generator for 6 hours or more at a time to charge while sailing?
Get a wind vane steering instead of using the autopilot?
Install a solar panel on my canvas dodger?
How do I test these batteries to assure that they hold up for 6 to 9 months?
Keep them until they are down and risk paying $ 800 to 1000 more for new batteries when in the Bahamas?
Or what else????

Thank you
Wolfgang, SeaLife E 43

[hellosailor]

Without trying ti grasp the whole picture...
If you are down to 12V after six hours of "sailing" I would think a battery bank that size is shot. Or something equally wrong.
If your shore charger has been equalizing Deka AGMs for several years, it probably has done significant damage to them, as Deka say not to do this, at all. 15 Volts will boil out their electrolyte and that could account for them not coming up to charge any more.
If your previous wet cells gave you 4 years, there is no reason to think AGMs would last any longer, and with a long trip to a place where batteries are going to be more costly, it would seem like a good time to replace them is now, before you go.
But not until you learn the entire charging system and ensure it is not mis-set or mis-matched, i.e. no equalizing unless the batteries are made for it. And all charging modes and voltages matched to those the battery maker specifies.

[a64pilot]

If you cannot fully charge AGM's to 100% every five to ten cycles, then AGM's are not for you, they are less tolerant of partial charging than FLA batteries are. If you can't fully charge at least every week, I'd go get FLA batteries at Sams club, Cosco, whatever you have access to. A 200 Amp GC-2 battery at my local Sams club is $84, 220 amp AGM, often over $300.
I don't know about island prices, but suspect batteries are cheaper here in the US


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[WolfgangSeaLife]

Just to clarify: When I say "shore power" I mean feeding the charger/inverter with 120 V shore power, not a shore-use battery charger. The Xantrex charger regulates the voltage for AGM batteries.

When sailing, the Autopilot uses 8 to 10 A. So 6 hours means using 60 A plus refrigerator etc, but in recent sailing I have sailed for 12 hours with autopilot before I had to charge for 1 to 2 hours and then sail another 12 hours. That's using up to 200 Ah in 24 hours and charging the same amount for 3 weeks in a row on my last sail.
Now how much damage did I do with running them down to dead empty twice?

[Stu Jackson]

The repeated comments about not using the battery switch when the engine is running are meaningless UNLESS you know how it is wired. If the alternator output (AO) goes to the C post of the battery switch, then it is prudent to not move the switch. If the AO goes to the house bank, you can turn the damned switch off when the engine is running and there will be no harm because the AO is connected to a battery.

This is simply boat electrical system design 101.

OEM 1-2-B Switch Wiring History Alternator/Batteries & "The Basic" 1-2-B Switch BEST Wiring Diagrams

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com