Let AGM batteries go to 0% charge

Hi all, so it appears I forgot to flip the electrical switch on the dock and my AGM batteries were fully discharged and sat that way for approximately a week.

Curious, how badly did I screw them up or shorten their lifespan?

I want to know how upset with myself I should be.

Thanks,
Mike

Tough to say. Just charge them back up, and move on. Nothing you can do at this point. I'll bet they will be fine.

twistedtree said:

Tough to say. Just charge them back up, and move on. Nothing you can do at this point. I'll bet they will be fine.

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Thanks for the pep talk...I needed that.

twistedtree said:

Tough to say. Just charge them back up, and move on. Nothing you can do at this point. I'll bet they will be fine.

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I agree completely. Put it past you and enjoy the boat. Since there really is no way to know how much the battery life is shortened, there is no sense in worrying about it.

I flattened mine completely, and it was a bit under a week before I was back at the boat to get them charged again. That was 5 years ago. I have been more careful since then, and have not repeated the 'event'. They seem to still have pretty much all of their original capacity etc. Maybe life has been shortened a bit, but I think they'll go for a few more years (touch wood)!

I also had a similar event deplete a new 8D AGM about 4 yrs ago.

Haven't noticed any appreciable loss of capacity. Charge it up and don't sweat it.

Charge it and monitor performance. They are pretty forgiving except for over voltage.

We bought our boat in 2015.
The two 8D AGM house batts gave it up this winter.
They were the older of our sets, the start batts being two interstate 4Ds.
Boat started fine three weeks ago after heated winter storage.
Charging occurred sporadically again during heated winter storage when I installed the new windlass and 120AC inlets and fresh water inlet and anchor washdown systems all at the pulpit area where I discovered an area of innerdeckrotfornextyearsprojectwhenIwilldismantleandtearapartthewholedamnthing!

Did I sound upset?
Sorry.

So anyway, the house batts are dead. Older than the starters per PO.
Start batts are also in question as PO indicated age as “due” and he is a smart man.
Replacing two house 8Ds with four Crown CR275 6v in series as they are 77ish pounds each vs 180 for the AGMs and have good guts per specs.
Tested the acid in the 4D interstate starters, and found one cell at 1150 vs 1275-1300 for all eleven others in the two 12v start Batts. Not bad for old batts....

Then, wearing my readers, I finally saw the tearoff dots indicating the purchase date of May 2004. Not 2014.
2004 ! and still operable with one of them still as NEW.
H.S..t!
14 years old and still all there! Yay Interstate!
Next weekend, I will post the model if I remember to shoot a pic.
Had I not already ordered the crown replacements for all, iwouldaorderedthesamemodelinterstates!!!
The Guys at Michigan Battery are bringing out and installing all of th Crown batteries, house and starts.
Not charging a dime extra. And they are paying $40 each for the old batts.
WOW.
My back is really impressed.
They are impressed with my Interstates and hope they can show well in the future too.
Will update on my batteries

The AGMs will be reported too as they made it 15 years to where we could anchor out a night last year.

Charles brand charger and old 60 amp delco alternators with original type regulators off Perkins 6.354 turbos charged these batteries.

Holy Cow.
Good Battery life.
Complete discharges certainly occured in 15 years.

Ask me after this season. I ran all $3,800 worth to zero early this winter as well. They charged up and appear to be okay, but I’m not cycling them at all yet. As mentioned, nothing you can do. Since almost none of us actually burn test for amp hours as it would require time and a very large resistive load, there is nothing to measure either.

MichaelB1969 said:

Hi all, so it appears I forgot to flip the electrical switch on the dock and my AGM batteries were fully discharged and sat that way for approximately a week.

Curious, how badly did I screw them up or shorten their lifespan?

I want to know how upset with myself I should be.

Thanks,
Mike

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Mike:

When AGM's are discharged in this manner they frequently suffer from sulfation, which decreases their overall capacity. The insidious part is you recharge them and they take a charge, although it often goes very quickly, too quickly. That's an indication of the decreased capacity. You don't realize it's an issue until you call on them to provide extended power.

If they are Lifelines, they can be equalized or conditioned, Lifeline details this in their Tech Manual, http://lifelinebatteries.com/wp-content/uploads/2015/12/6-0101-Rev-E-Lifeline-Technical-Manual.pdf on page 21. Provided they weren't too old, I've used, on many occasions, this approach to resurrect Lifeline batteries that were fully discharged and left in that state for some time.

This article covers the subject https://www.proboat.com/2016/10/solving-sulfation/

Thanks Steve, they are not Lifelines. They are Mastervolt batteries and they are about 6 months old.

I have a Balmar Smart Gauge on them. Wonder if it will show a full 100% charge when I am next on the boat. Or would it show 100% regardless.

Hmm...

It is what it is. Hate to say that. Recharge and see how they do. May of cut some time off in the long run but see if they hold a charge now.

Here’s my dead housebank story.

During my first winter of ownership, I had the boat hauled and turned off all the breakers. I should have fully charged the AGMs and disconnected all the cabling. Between the parasitic loads I didn’t know about and several days of temps at or below zero, the house bank was done for. The four 8Ds would temporarily recharge but they wouldn’t hold. I took them to a shop and had an equalization charge done. Still would not hold a charge.

Initally, it pissed me off royally, but now I’m glad they’re gone. (I regard 8Ds like some folks think about silicon caulk: not on my boat.) Losing them gave me the chance to spend a lot of money and time redesigning and upgrading the electrical system: new 305 AGMs, which are much easier to handle, relocated from the worst possible place to have house banks (outboard of both engines) to a much easier place to access. New inverter/charger, isolation transformer, monitors, switches, fuses, cabling, terminations, remote regulators, etc. It is SUCH a better design and now I can access the outboard sides of both engines without needing two elbows on each arm. (Photo taken before the clutter was cleaned up.)

angus99 said:

Initally, it pissed me off royally, but now I’m glad they’re gone. Losing them gave me the chance to spend a lot of money and time redesigning and upgrading the electrical system...

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Now that is a "cup is half full" outlook.

MichaelB1969 said:

Now that is a "cup is half full" outlook.

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Yeah, but I didn’t even cite all the reasons I’m glad. The old cabling was corroding, some of the terminations were bare and there was a lot of welding cable lying in the bilge carrying heavy current . . . some of the sheathing was deteriorating from exposure to fuel. It’s all gone and the new cabling has proper heat-shrink terminations and is as close to ABYC as I could make it. Plus, I got to know the boat’s electrical system to a level of detail I could never have understood before. Plus, I’ve limited the potential for galvanic corrosion, shocking swimmers and reversed polarity by replacing the entire bonding system and using an isolating transformer.

But if all that’s not enough to rationalize the time and money, I can now make a pot of coffee without cranking up the genny.

MichaelB1969 said:

Thanks Steve, they are not Lifelines. They are Mastervolt batteries and they are about 6 months old.

I have a Balmar Smart Gauge on them. Wonder if it will show a full 100% charge when I am next on the boat. Or would it show 100% regardless.

Hmm...

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I would contact Mastervolt and see what their recommendation is on equalization. While it can be hard to find, most manufacturers will have that information somewhere.

AGM's handled being Deep Cycled much better than FLA. I suspect you should be fine.

angus99 said:

But if all that’s not enough to rationalize the time and money, I can now make a pot of coffee without cranking up the genny.

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Heck more than that! Your instillation provided the ideas and inspiration for me when I did mine last year. I used the US Batteries AGM L16s. So far they have been great.

Has anyone tried a de sulfation device?


Answer To The Question: Battery Desulfators - Do They Work? - Blog -

https://www.impactbattery.com/blog/2013/02/battery-desulfators-do-they-work/


Feb 22, 2013 - I personally would avoid high voltage pulsers and stick to the frequency based battery desulfators. Putting up to 60V into a 12V battery, even if ...

MichaelB1969 said:

Thanks Steve, they are not Lifelines. They are Mastervolt batteries and they are about 6 months old.

I have a Balmar Smart Gauge on them. Wonder if it will show a full 100% charge when I am next on the boat. Or would it show 100% regardless.

Hmm...

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Another member suggested contacting MV, and I agree, however, how much tech info you can get from them is a bit of a wild card. If they have guidance for equalization that would be worth the effort with them being so new.

Before you try that, however, see what sort of capacity you have, they may not be sulfated.

If you had a conventional amp-hour meter I'd say yes, this will register far less amps going in than the rated capacity of the battery if they were heavily sulfated. However, the Balmar is not a conventional amp-hour meter, so I just couldn't say; it's not a meter I use.

The bottom line is determining how many usable amps you get from the bank, that the meter will tell you and when compared to rated capacity you'll know if they've been affected by the deep, extended discharge.