Did I kill my house bank? Electrolyte was low.

[MarkSF]

I went to check the electrolyte on the house back today, and it was below the top of the plates. I turned the charger off, added distilled water to bring it above the plates, and turned the charger back on (Pro Mariner).

Prior to this I noticed recently that the float current had been a little high, 0.6A.

Now the charger has been sitting in Conditioning (AKA absorption) mode for 2 hours, and the current is 8A for two batteries, 4A per battery, and not dropping - if anything, it's creeping up. There's a lot of outgassing too.

Initially there was a smell of hydrogen sulphide, but that went away quite quickly.

I had to leave so turned the charger off. I was scared of overheating the batteries if I left it like this.

These are a pair of 6 year old US Battery 24DCXCs, in paralled. I guess they didn't have much life left.

Have I killed them? Or were they about done anyway?

[S/V Illusion]

Hard to tell absent seeing the voltage curve, internal resistance and load test results, any of which would be more definitive than any guesses people offer here.



I wont guess but will suggest one additional consideration you should investigate - that being a malfunctioning charger (controller) can often kill the batteries prematurely. Cooking the electrolyte as you did could be the fault of a bad battery or a bad charger (or both) so before replacing the batteries, make sure the charger won't kill new ones too.

[sailorboy1]

well when my last set starting "accepting" more charge at absorption than they used to it was the start of the end

[s/v Jedi]

First fully charge, then add water.

You can try to first discharge 50% or so, then charge and see if that works better.

[Wotname]

Batteries - once they start gassing, they are charged. Pumping more current into them until there is lots of outgassing is detrimental and adds nothing to the SOC.

Hydrogen sulphide - this a significantly dangerous gas and can easily kill you. While the odor threshold is very low (< 1ppb), at higher levels of 100 ppm, it kills your sense of smell thus making you unaware of higher (and deadly concentrations). At 1000ppm, a single breath is lethal.

See more https://en.wikipedia.org/wiki/Hydrogen_sulfide

[boatpoker]

Once the plates have been exposed it is highly unlikely they will last much longer. If the batteries are getting hot and you can smell the sulfur dioxide you are getting into the area of possible explosion or at least a case fracture and a lot of sufuric acid to clean up. Google battery explosions.

[Wotname]

Originally Posted by boatpoker

........... If the batteries are getting hot and you can smell the sulfur dioxide .........

Sulfur dioxide????

[boatpoker]

Originally Posted by Wotname

Sulfur dioxide????

Google battery gasses, there are several different gasses produced. The sulfurs are the stinky ones.

[Wotname]

Originally Posted by boatpoker

Google battery gasses, there are several different gasses produced. The sulfurs are the stinky one.

[Stu Jackson]

Mark,


You didn't kill them,, they had a happy life with you.


That longevity is very good.


Just get new ones, those DSCXs are great.

[Adelie]

Kill them? Probably not.
Shorten their life some? Probably.

Put some water in them and cycle them normally for 10 or so cycle. Equalize. Then do a capacity test.

[roland stockham]

You don't say what the battery capacity is or what the charger voltage is so I don't now if those charge rates are high, normal or low. Batteries can stand some drying but it depends on time. Water can go low for a day or so if the plated do not dry fully and the battery can still recover with little loss. I would do a few cycles before writing them off. If they go back to taking normal current in bulk charge you are probably fine to keep using them but they may have lost a few % of capacity.

[Apollo366]

I'd say if they're gassing at this stage I'd say they're toast and can be very dangerous to continue to charge.
When batts are overcharged they create Hydrogen gas and we know how bad that is, esp in an enclosed boat!

It does sound like your charger is bad too, I'm assuming your boat is 20+ yrs old, and charger is about that old, if so replace now and new batts too.

Do not continue charging/gassing the bats, no good will come of it.

I was in submarines and we had really big batts & treated them very tenderly, had a special meter that showed H2 levels in battery compartment, ANY reading was cause for great alarm and quickly shutting down or lowering charge rate.

Capt Wayne

[Mike Banks]

I think you should probably replace them. H2S is NOT a good sign.

That H2S smell is decomposing sulphuric acid. It happens when the acid levels become very low and concentrated. Adding distilled water might fix the problem, but once the battery is as charged as you can get it, if you want to take a punt and spend some more money, take out the batteries. Wear rubber gloves and goggles, or even better, a full face mask. Put some washing soda concentrated solution in a large plastic bin or bucket, and empty the battery's electrolyte into the bucket. Add more soda until it finally stops fizzing. You can now safely dispose of it--the sodium carbonate is now sodium sulphate, and the liquid remaining is now water.


Now wash out the battery using a garden hose--give each cell a good flushing. Put the battery upside down on blocks of wood.
While the battery is flushed, drained and empty, test the battery across the terminals with an ohm meter.

There should be extremely high resistance. Older batteries one could test individual cells and replace any faulty ones--but now one tests the whole battery for internal short circuits. That is why the flushing--many internal short circuits are caused by lead and lead sulphates and oxides dislodging from the plates and accumulating in the cell casing--eventually reaching the bottom of the plates and causing a full or partial short circuit.

If no problems, then refill it with NEW battery electrolyte and give it another charge.

Dislodged material from plate surfaces is why one should never fast-charge flooded lead acid cells. Fast charging can also warp some plates, making them contact one another.

One hundred amps is a lot of charge for a flooded lead acid cell bank as small as yours. Sixty to eighty is more than plenty and if one is using a slower charge over many hours such as comes from wind, solar or towed turbine, fifteen amps or less, that is even better still.

One should test one's batteries using a hydrometer at least every fortnight, and once a week is better. Top up using distilled water (you can use air conditioner condensation water or melted defrost ice from your refrigerator if you run out distilled water at sea.

That is why it is important on vessels to have easy access to batteries, fresh water pumps and filters, sea water strainers, filters and pumps etc. Get into a routine of checking and do not omit doing it--because not doing it can be an expensive oversight. A complete boat check of everything takes one hour or less.

[Popcorn]

Appolo, what was the name of your sub. Blenny and Sailfish here.