Conductive Liquid for Battery Cell

Don't short the bad cells, just link 6 of the good ones in series.

Before doing that you might try to bring the bad cells "back to life". Use a current limited charger (that won't smoke if overloaded) and just apply about 5 amps directly to the 2V "bad" cells. A 12V headlamp bulb in series with a 12V charge might give you about the right current.

About 10 hours of change on the bad cell then top-up charge the whole battery.

Worth a try???

Dear Friend

Could you pls. tell, what you mean by "bad cell", whether broken/leaking or inadequate charge or something else. Based on this, further suggestions can be made.

Thanks and regards

Ashok Toshniwal, Bangalore, India

Chris,

Johny451's suggestions have merit, however I gather from your question that the individual cell terminals are not readily accessible.

You could try CAREFULLY cutting away the top of the battery case above the bad cell, to expose the terminals. Alternatively, just overcharge the whole battery to (possibly) get the bad cells revitalised. Be aware that you'll be producing hydrogen and oxygen (an explosive mixture of gases) from the good cells, and will need to monitor the electrolyte levels (top up with distilled or demineralised water) and temperature in all cells.

Other options:

1) In Australia there is a battery conditioner produced by INOX, which is good for reviving mechanically sound batteries. The label says it contains not more than 5% Cadmium, and the instructions say 120 mls per cell for 201-300ah, so you'd probably need about 240mls per cell. If you can't get the INOX product you may be able to use the above info to find or make an alternative.

2) There are some useful tips on the internet for reviving lead acid batteries. I don't have the URLs handy, however the gist is to drain the electrolyte and save it (it's sulphuric acid, so be careful and use a suitable container, probably plastic), flush the batttery/cell to remove any lead sediment that may be shorting the plates (use demineralised water, especially for the final flush), and strain the electrolyte before returning it to the battery (alternatively use fresh battery acid), then give the battery a long charge.

2) If you do short the cells, BE CAREFUL, as even bad cells that size may have quite a lot of energy which could be released suddenly as heat if shorted.

3) The best way to short the cells would be to find the cell terminals and short them, after draining the cell of residual power by placing a resistance (eg torch bulb) across the terminals, and if practical draining the cell of electrolyte as well.

4) You could use Brine (saturated salt solution) to short the bad cells. However if the cell is "bad" because of lead suphate build-up you may find that you are left with a high resistance instead of a short. Also, you'd have to check whether the brine would react with the lead plates or lead sulphate to form an insulating or high resistance coating.

5) An alternative to Brine would be to use a very low melting point metal, eg Field's Metal (see http://en.wikipedia.org/wiki/Field%27s_metal ), Wood's Metal, or one of the others mentioned on the wikipedia Wood's Metal page.( http://en.wikipedia.org/wiki/Wood%27s_metal ). However, you may still have to contend with lead suphate resistance. You might be able to reduce this by using something to scratch/scrape the plates after draining the electrolyte.

Thanks Ausvirgo for the taking the time to write such useful comments. You are correct in that the individual cells are the problem, not the battery. I have tried to "equalize" them back into service with a long (48 hour) extended charge at high V with no luck. The cell just refuses to hold a charge (as measured by the hydrometer which shows no increase). In regards to the other points,

1) I don't have access to this here...

2) That could be an interesting option. I might try that this weekend. Sounds like a good bit of dirty work....

3) agreed

4) I hadn't thought of the suphate build up problem. I don't think that this is the problem though as the battery is new. But definitely this is something to consider.

5) Another difficult thing to get here.

Regarding the Epsom salt comment, I'm a little scared to introduce new chemistry but I'll give it a try before cutting the batteries open.

Thanks again to all the responses!

I have successfully used Epsom Salts to rejuvenate batteries, but it doesn't always work and I am not sure of the actual chemical reaction involved.

If these are new batteries supplied by a reputable vendor (i.e., one who does not store batteries for extended periods or sell rejuvenated batteries as new batteries), sulfation is not a likely issue. I would suspect mechanical damage due to improper handling during shipping (or poor manufacturing), in which case there isn't much that can be done, unless you can get inside the battery and short out the bad cells, reducing the voltage of that particular battery.

Dear Friend

48 hours is probably a short duration for the kind of problem, you are facing. It might take more than a week or so. Remove the electrolyte completely. Fill fresh electrolyte. then charge at low current.

Thanks and regards

Ashok Toshniwal, Bangalore, India

As I said, the Epson salts is a tip from the late forties, my fathers actually and I bet he was told by someone else. I guess it bust be safe. A heck of a lot of lead-acid battery faults can be traced to sulphation, especially if it has sat discharged for any lenght of time.

RRV

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goodluck

This is probably a last ditch solution but if everything else fails and you just can't get the battery to work, you might try draining the electrolyte and then carefully cutting the top off the battery and getting to the plates themselves and see if there is a broken bond due to mishandling. If you find physical damage you can try soldering the bond back together, reassembling the battery (you'll probably need to use something like silicone caulk to glue the top back onto the battery case) and refilling it with fresh electrolyte (if available, if not you may have to settle for the old electrolyte).

Worst case, melt the lead down and cast bullets with the lead.

BTW, EDTA is an even better sulfite rejuvenator if you can get hold of it.

Chris,

You haven't stated what type of batteries you have. Your description could apply to acid, alkaline, industrial NiCd, or a variety of other designs. Any suggestions to modify or restore the chemistry will end in disaster if the wrong type of electrolyte is introduced.

IF these are lead-acid batteries, you may be able to restore the dead cells. Shorts are most often caused by sediment (or a small piece of plate material) in the bottom of the cell shorting across the bottom of the plates.

First, check the specific gravity of the cell, and compare it to the manufacturer's description. For most lead-acid batteries, the specific gravity of a fully charged lead acid battery will be either 1.215 or 1.250. If the measured SG is within 10-15 points, of full charge, the cell is likely shorted. If it is more than 25 points low, the cell is discharged.

For a discharged cell, if an equalizing charge does not restore capacity, add dilute sulfuric acid to bring the specific gravity to the manufacturer's stated design value. An equalizing charge should then give you the capacity you seek. Lead acid batteries are designed for 118-120% of nameplate capacity, to provide a full life cycle. Even if the plates are sulfated, there's usually enough excess plate material to allow the chemical reaction to take place. You may not have quite the 550 AH capacity, but at least it will work.

For a shorted cell, the following procedure will often restore a the cell to service.

1. Using a bulb-type hydrometer or other bulb-suction device (I use a turkey baster with a piece of rubber gas line on the end), suction out the liquid from the bad cell. Save the electrolyte in a glass container. DO NOT turn the battery upside down to drain.
2. Using pure water (preferably from a reverse osmosis filter system, but distilled water will also work), fill the cell.
3. Suction out the water, getting the suction tube as close to the bottom of the jar as possible. Do not mix the water with the electrolyte previously removed.
4. Repeat the fill & empty procedure, using new water each time, until the removed water is crystal clear.
5. Use cheesecloth or finely woven cotton cloth to strain any solids from the saved electrolyte, then pour the electrolyte back into the cell.

Repeat the entire process for each dead cell in the battery. When all of the cells have been cleaned, place the battery on equalizing charge.

Equalizing charge procedure:

1. Apply 2.5 volts per cell (7.5 volts for a 3-cell battery) for 24 hours, or until charge current drops to <0.5 Ampere.
2. Regularly monitor the temperature of each cell. If the temperature of any cell reaches 130ºF, stop the charge. If you don't have a thermometer, 130 is about when you can't hold your hand on the cell without pain.

Full restoration is a gradual process. You may need to do several discharge - equalizing charge cycles to restore capacity.

Thanks all for the good suggestions

pwrtothepeople, the batteries are in fact lead acid (Surrette) batteries. You make a good comment on the fact that if it was a short the specific gravity should still be relatively high. In fact it is not. The two bad cells (1 each on two different 6V batteries) is below what I can read on my float hydrometer (<1.10) while the other cells are around 1.25. When I did a long equalization the voltage would go up on the battery but the bad cell's SG didn't move at all on one of them and just barely started to measure on the other (1.10). From this, I gather that you would recommend to try and add some acid and see if it will take a charge after another equalization.

If that doesn't work then it seems the recommendation from the group is to not short with a saline solution but rather open it up and mechanically short the cells. This sounds like more work but if it work....

Thanks again to all.

Hi again,

A short could make the SG low, if it is bad enough to a) discharge the cell, and b) stop the cell getting enough voltage to charge when the battery is charging. If the cell is badly shorted the battery should behave like a battery with one less cell and a higher internal resistance. Even while being charged with a low current ( to minimise the effect of resistance) it would have a voltage of less than 6 volts.

pwrtothepeople's suggestion for cleaning out sediment might be worth a try if fresh acid doesn't work.

Epsom salts is magnesium sulphate, probably works similarly to the cadmium sulphate battery conditioner I mentioned, but not as well or they wouldn't use highly toxic cadmium sulphate. Might be worth it before trying shorting the cell.

I agree that a new battery shouldn't have sulphation, UNLESS it also has a short, causing the cell to be totally discharged, which would encourage rapid sulphation.

GOOD LUCK, and let us know how you go!