Will these batteries survive?

[Steve L22188]

It's been a brutal winter here in the Midwest. Between the weather and my work schedule, finally got to the boat yesterday to uncover it. Discovered, to my chagrin, that the marina had unplugged my shore power to plug in their bubblers. I don't know how long the batteries set with no charging -- I suspect it was at least two months.

Checked the batteries and discovered one read 8.10 volts and the other read 10.13 volts. Both batteries had plenty of water in all the cells. These batteries are marine deep cycle and they're about 3-4 years old. They've performed well.

Got the shore power back on and when I left the boat, the charger was working and doing its thing. I'll check again on Sunday to see how the batteries look.

But wanted to get the thoughts of the wise folks here -- what are the odds that the batteries will survive? Do you think the charger will bring 'em back -- or am I looking at buying two new batteries this Spring?

Is there anything I should or shouldn't do to try to make these go at least one more season? Thanks to all!

 

[Snotter]

With voltage readings that low I'd wonder if the specific gravity of the electrolyte got so low that the batteries froze. When batteries freeze the outside case gets wavy.

If your batteries come up to 13 volts or so, I'd recommend checking the specific gravity in the cells. There is no need to guess about the condition of your batteries.

 

[tkanzler]

Probably depends on how hard they've been used in the past (how deeply they've been discharged, and how many times), and how much you plan on depending on them in the future.

If this pair of house batteries are also used to start the auxiliary, and if there is no independent backup start battery, and given the age of them and the anticipated lifespan of typical lead-acid batteries, then I'd replace them if it were me.

You're going to have to replace them sooner or later anyway, and you are closer to sooner, just from age. I use a pair of group 24's for house batts, and keep another isolated but charged for backup engine starting.

I can go all day crossing Lake Ontario with autohelm, radio, cold plate in the ice chest, and a notebook computer on an inverter with nav software running, and still start the engine (3 cyl Yanmar) with gusto off the same house batteries, but I like having the extra backup battery. The middle of the lake is a lousy place to need a jump start. Point being, of course, I don't care to take chances I don't have to with the ability to start the engine.

 

[Roger Long]

Keep in mind that, if they froze or the plates were weakened or distorted by the extreme charging cycle, two plates touching in the battery could cause them to explode. You don't have the instant chlorine gas issue when the acid hits the salt water in the bilge to worry about but a mist of sulfuric acid, spray, mechanical damage, medical evacuation, and clean up could be an inconvenience on an otherwise pleasant afternoon sail.

The mechanical separation of the plates provided by AGM batteries is just one of several reasons why I believe AGM stands for "Absolutely Gottahave Mandatory" The extra cost is insignificant in an overall boat budget.

Talk to the friend of mine who spent two weeks in the hospital after a battery blew up in his face when he set it down on the deck. It wasn't even connected to anything or charging. The bump just caused two weakened plates to touch and self short circuit.

 

[Don S/V ILLusion]

Re-read Roger's post above and then reconsider leaving the charger on, especially while the boat is un-attended.

 

[sailingdog]

The real issue is whether the plates sulfated or not. Wet Cell batteries wil tend to form lead sulfate crystals if left discharged for long periods of time. Cold weather can exacerbate the situation IIRC. Try charging them and then see if they hold a decent charge. If so, then they're probably okay... if not, then get new ones.

 

[lehighsail]

A good thing to pick up and keep on board is a battery load tester. Its the size of a vegetable grater and looks like one. Harbor Freight has it on sale now for $19.95. You can instantly test the battery and lets you know if it is charged and will let you know if the alternator is charging the battery when running.

 

[Ron20324]

I'd try to have the marina get you new batteries if thier actions caused them to die. They could at least sell them to you at cost. They should know better than to disconnect shore power. They at least should have contacted you first. BUT, as a member of our dock committee I see our bubblers are 15-amp plugs. If they disconnected your "shore power", it must have been in the 15-amp plug- not the 30??? Here, we do not allow unattended 110/15-amp cords plugged in unless the owner is present. All too often people put the skimpy 15 cords on the 30-amp service with an adaptor. NOT GOOD, and NOT ALLOWED!!!

 

[Steve Dion]

I would have my doubts about the batteries being in very good shape. Obviously we do not know exactly when the charger was disconnected, but fully charged batteries should have lasted at least 2 months off the charger if they were worth anything.

Now is a good time to re-evaluate your DC system (charger, battery chemistry etc)

 

[Rick Sylvester]

No question.

The marina owes you a set of batteries.

If I was paying for the electricity to run those bubblers I think I'd be doubly outraged.

 

[txtowman]

someone unplugged a boat in my marina last fall. It almost sunk and ruined 2 brand new engines.

I would think any marina employee would know that, and at the marina I was at in Kemah(houston) they walked the docks at night to be sure all boats are ok.

 

[Benny]

You ask about chances, I give it 80% to 20% that they are toast. The age of the batteries has a lot to do with it.

 

[Stu Jackson]

Forget about the age. If they were severely discharged and froze, even if brand new, they are most likely toast.

 

[Steve L22188]

Update on the batteries after charging

Thanks to all of you for your thoughts. Returned to the boat today after the battery charger had been doing its thing for about 5-6 days.

One battery read 12.89 volts and the other read 12.90 volts. It seems I've read that a really good battery will show over 13 volts -- but I'm OK with these numbers based on the previous readings. And these new readings aren't that much different from what I got last year. I'll keep an eye on them during the summer.

Thanks again.

 

[sailingdog]

A fully charged 12 VDC battery will be anywhere from 12.6-12.7 VDC unless there is a surface charge on the plates.

Thanks to all of you for your thoughts. Returned to the boat today after the battery charger had been doing its thing for about 5-6 days.

One battery read 12.89 volts and the other read 12.90 volts. It seems I've read that a really good battery will show over 13 volts -- but I'm OK with these numbers based on the previous readings. And these new readings aren't that much different from what I got last year. I'll keep an eye on them during the summer.

Thanks again.

 

[rardiH36]

Resting Voltage Info For Battery Condition Estimation

It seems that you are measuring the voltages during or immediately after charging?

From what I have read (from previous posts on this forum) and observed on my own boat, its the open circuit voltage at room temperature several ours later that's needed to give a good indication of battery condition. See "6. Terminal Voltage" in the below link for info. In my case, for example, during the afternoon when my solar panel is charging at its max into my two batteries via dedicated and isolated charge controllers for each one, both my battery voltages typically show ~ +/- 14V. When I disconnect the charge current the voltages gradually decrease and the next morning with no load on them during the night, Bat#1 typically will read about 12.5 v, and Bat#2 about 12.7v. They will then stay there for several days without further charging. According to the chart in the attached url (one of many charts on the internet) my bat#2 is in very good condition. Bat #1 is probably only holding about 80-85% of its "new condition" charge. In real life I can tell the difference between the two. Bat#2 revs up the starter motor robustly. Bat#1 noticeably strains in comparison.

When I bought my boat, as with you, the yard had not be diligent about keeping the AC cord plugged into the boat's charging system. Both batteries were the same brand with the same production date. I recall measuring 10.8v on bat#2 and 10.1 on bat#1. This corresponds to why bat#2 is now the stronger of my two batteries.

http://en.wikipedia.org/wiki/Car_battery


http://en.wikipedia.org/wiki/Car_battery

 

[Steve L22188]

Reading right after charging

Yes, you're correct, the reading is from right after turning off the battery charger, and turning the battery switch to "Off". (likely didn't need to do that?)

I understand the real test is after sailing all day and we want to start the iron genny to come home -- will they turn the engine over? (We'll test that at the dock after a work day or two with the charger turned off. No need to do that first test under actual conditions)

Thanks.

Steve

 

[sailingdog]

Since these are wet cell batteries, what you probably really should do to see what condition they're in is to sample the electrolyte from each cell with a hydrometer. Once you know the specific gravity of the cell, you can see how well charged it really is, withoug having to worry about surface charge levels on the plates and such.

Yes, you're correct, the reading is from right after turning off the battery charger, and turning the battery switch to "Off". (likely didn't need to do that?)

I understand the real test is after sailing all day and we want to start the iron genny to come home -- will they turn the engine over? (We'll test that at the dock after a work day or two with the charger turned off. No need to do that first test under actual conditions)

Thanks.

Steve

 

[Maine Sail]

I understand the real test is after sailing all day and we want to start the iron genny to come home -- will they turn the engine over?

Steve

Steve,

If your batteries won't start your engine it means you have drawn them waaaaaaay below a 50% state of charge. Doing this on a regular basis will lead to very short lived batteries..


Here's a link to an earlier discussion on measuring a state of charge using open circuit voltage readings. It should help put it in perspective..

http://forums.sbo.sailboatowners.com/showthread.php?t=106778&#post614776

 

[Ron McCoy]

In Nigal Caulder's book, Boat Systems and Maintenance he'll tell you the only way to test a battery is to load test it. This is accomplished by cranking the engine (with fuel shut off valve closed so as not to let the engine start), turn the ignition key and watch the engine voltmeter. If it holds for 10 seconds without fading below 12 volts, the battery is OK. A weak battery may start strong but in seconds will rapidly fall off holding voltage. Batteries are a strange beast - they give false, misleading and sometimes truthful answers. Knowing which answer is correct is the hard problem.