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Captain Dave
Captain Dave, Marine Mechanic
Category: Boat
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Experience:  USCG Licensed Captain, 20+ Years Boating, Fishing, Maintenance and Repair Experience
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I have two marine deep-cycle 12v batteries, 125 amp hours

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I have two "marine" deep-cycle 12v batteries, 125 amp hours each (Max brand, from Walmart) that were hooked up to a solar panel at a remote cabin. There was some corrosion on the connections so the solar panel couldn't recharge them, and through neglect they were allowed to discharge completely. To add insult to injury, they then sat for several months while I worked on other priorities. The water was way down in all cells on both batteries, but I don't think the top of any lead plates was uncovered. I filled them to the bottom of the filler necks with distilled water (...yeah, I know, that diluted the sulphuric acid mix, and further reduced the charge, but I didn't want to risk further water loss during charging).

I realize that they may be completely shot, good only for replacement cores, but there is a chance the primary problem is sulphation, so I'd like to try to resurrect them with my new BatteryMINDer model 12117 (a 1.3 amp, 12v charger/mantainer/desulphator). However, the BateryMINDer won't even recognize a battery that has less than 11v RESTING (i.e., 8 hours after being dicsonnected from a charger). I checked the first battery with my tester, which pegged it at about 6 volts. That was so low my Schumacher 6/4/2 amp charger wouldn't even recognize it as a battery, thought it was a mushroom, I guess. I took it to O'Rileys, they were nice enough to slow-charge it for 3 hours, got it up to where the Schumacher charger would work, and now it's been charging for 28 hours at the 6 amp rating, which should be enough to give it a full charge...if not gunked up by sulphation or other problems. Whatever the problem is, the Schumacher showed it as 25% charged after about 10 minutes...and it has never changed. It's still showing 25% charged. I noticed tonight that the charger is warmer than it normally is when charging, almost cooking hot, and there is a noticeable "fizzing" sound coming from the battery. I disconnected it, the multimeter now shows it as 12.25v.

I'll leave it disconnected until tomorrow morning and check the resting voltage. If it's still above 11v I'll hook up the BatteryMINDer, manually start the desulphation process, give it a month or so to blast off some of the sulphation, and then see if it will hold a full charge.

But here is the real question: Should I be hearing an obvious hissing and bubbling sound from that battery? I realize that some amount of hydrogen is produced during any recharge cycle, but should it be that much, that loud? It concerns me.
Chat Conversation Started
heavy_chevy_396 :

You are supposed to add just water when it needs it, because the acid when discharged is stuck to the plates. Actually a completely discharged battery will have just plain water in it. Usually batteries have numerous cycle lives, that is they can become discharged and recharged numerous times before they run out of service life. What usually happens after so many cycles is the material from the plates flakes off and falls to the bottom of the battery where it accumulates untill it actually shorts out the plates. One way to resurrect a battery to to completely drain it of all power. Then it will be just plain water in it. Then turn it upside down and drain out all the water and use a water hose and add some more water and try to get all the debris in the bottom washed out. When done just fill with plain water and charge.You don't need to add any acid because the acid is stuck to the plates on a discharged battery. If it is bubbling when you charge it it is probably overcharging and boiling. Since you have a voltmeter check each individual cell. Place the postive lead of voltmeter on positive post and negative lead in the cell just next to the positive post into the water/acid solution. It should read about 1/6 of total battery voltage. Next move both leads down one each and then again untill you actually have 7 tests. One wiill be almost zero, just ignore that one, I believe it will be the last test when the neg lead is on the neg post and the pos lead in the cell next to it. If you have 1 or more cells that are like less then 0.2 volts and all the others 1.2 then them low cells are shorted.

Hello. It appears that Heavy Chevey has given you all the information you need; the fact that it is a marine battery should not make any real difference here - the deep cycle batteries are designed to be fully discharged and then charged again. Be sure you have good ventilation when you charge, since hydrogen gas (explosive) will be created.
Customer: replied 6 years ago.

Hey, guys. Knock this off. I waited three hours for an answer to the question, "does a noticeable hissing and bubbling indicate more than usual gassing" (or words to that effect). I NEVER got an answer to that question. Heavy Chevy's answer may be a good one, but not to the question I answered. I finally got tired of waiting, unplugged the charger, went on line and did a lot of research to find my own answer.


Dave's response that good answers aren't free is a cop-out. I didn't suggest that the type of battery would make a difference, I only included all the specs for your info, and to explain why it was taking so long to charge my battery.


I was willing to pay $23 for a quick, accurate answer to the specific question I asked. HC's answer was not quick, not easily interpreted, and not to the point. He said the sound indicated one or more cells were shorted and overcharging. NOT TRUE. I've now had the battery tested and no cells are shorted, just badly sulfated. I may not be able to resurrect this battery(or its identical twin), but I at least now know how to proceed, no thanks to either of you.


I don't think I owe anyone $23 for the nonresponsive and inaccurate answer I was given. If you think different, I'll give you a week to have someone from the main office contact me, to try to convince me. Otherwise, in about a week, I'm going to cancel my PayPal deposit. I am NOT going to accept your answers. If you think I am being a crank or a crook, I don't. I just don't think I should have to pay for nothing I could use.

Hey, that's fine. The way this site works, YOU decide if the answer is useful to you or not, and if not then you don't pay - end of story. In Heavy's defense, I will tell you that many times the customer is looking for a lot more information than a simple answer, and he was attempting to provide you with more value. I suspect it took longer than usual because your particular question didn't fit very well into any of the categories, so it wasn't seen right away. I can tellyou that in the Marine Electronics and Boats sections, the typical response time is a minute or two.


You currently have a deposit paid and it remains in your account, under your control. You can save it there for the next time you have a question, or you can request a refund at any time.

Take a look at this link:

Sulfation...The process can often be at least partially prevented and/or reversed by a desulfation technique called pulse conditioning, in which short but powerful current surges are repeatedly sent through the damaged battery. Over time, this procedure tends to break down and dissolve the sulfate crystals, restoring some capacity

Captain Dave, Marine Mechanic
Category: Boat
Satisfied Customers: 3847
Experience: USCG Licensed Captain, 20+ Years Boating, Fishing, Maintenance and Repair Experience
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Customer: replied 6 years ago.

Thanks, XXXXX XXXXX A darned nice answer, and very polite, in response to my somewhat surly ranting. I know a lot about desulfation, I've been studying it for months, which is why I bought the BatteryMINDer unit. It's reported to be tops in doing a continuous job of fighting sulfation in healthy batteries by using a random pattern of low voltage, high-frequency pulse-technology surges -- it has even been used by a holy host of folks to restore apparently dead batteries. Problem is, the "dead" battery must be brought up to a minimum resting voltage of 11v before the BatteryMINDer unit will recognize it as a battery...and my battery is refusing to stay that high. It may just be beyond the pale. I'll keep trying for a few days, and if I can't get it to hold even the minimum charge I'll just use it as a replacement core for one of the new batteries I've already bought. Then I'll try the other one.


Regardless, your point is well-made. I buried my question in a lot of extraneous data, and Heavy Chevy tried to address more than my main question. My fault, not his. I'll accept the answer(s) you both have given me. ...Can you share credit with HC?

Thanks. XXXXX will get the fee; he did the heavy lifting!

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