How to revive my lead/acid batterie bank

[laforge24]

Hi
I have a 980Ah lead/acid batterie bank , 12x2V, tubular special solar !!
They are now 10 years old and have not been used correctly over the last
year, voltage without charge had dropped to 2V per element,
I have tried to discharge them to 1,85V per element,
so as to start a correct charge to REVIVE them,
So at this moment they are being charged by 1080Watts solar
DIRECT/ meaning without regulation, as to give them a BOOST
and mix the acid due to bubbling !!
I had hoped to see the voltage go to say 30Volts as it is a 24V system,
but now after 3 days of full sun the voltage does not exceed 29.2V
Not bad but is this sufficient?
I suppose 1080 parted by 24 will give 45Amps max!
which is 5% of the batterie bank ?
These batteries are in good condition ,,,
what would you propose? your opinion ?
THANKS
PS this is not my boat system but my homestead!

[dennisail]

You can halve your battery bank and boost the 2 half banks with your solar separately. That will allow up to double the current to flow through each cell.

[laforge24]

Yes, that is what I thought too, but complicated
the 12V panels are joined in specific junction boxes in which are
all the diodes and other ,, to come out as 24V
the batterie bank could only be divided in 2 x 12V,,,,

But more important , up to what voltage would you charge that bank
I have now seen that the voltage does go up the 4th day at 29.5V
Maybe it just needs longer, BUT what should be the maximum Voltage ??

[Andrew Troup]

I think anything over 31V would be pushing them too hard without special equipment

I would personally settle for 30V for lead acids, in the absence of a charger with a special conditioning programme which might safely push it as high as 32.4V

(but I am not familiar with your particular tubular items)

Bonne chance !

[laforge24]

Originally Posted by Andrew Troup

I think anything over 31V would be pushing them too hard without special equipment

I would personally settle for 30V for lead acids, in the absence of a charger with a special conditioning programme which might safely push it as high as 32.4V

(but I am not familiar with your particular tubular items)

Bonne chance !

Thanks for your technical input
So my last measure of 29.5 is close enough to your 30V
at that moment/voltage I disconnected the solar charge and will be
checking 24 hours after complete disconnection what the end voltage
is going to say, I am sure it has done them well,
If not i will put them on direct charge up to your 30V
Thanks again

[dennisail]

How long were they at the high voltage for? It can take several hours for the equalization to work.

[HappyMdRSailor]

OK....

If I have read this correctly...

Your wet lead acid bank is 10 years old???
I think you got your predicted life cycle and then some...

One trick utilized by the "used battery" vendors to recondition/save/bring back to life/weed out the bad batteries collected....

This procedure is for information only.... Following the steps assumes you are accepting all risk and responsibility

Bridge rectifier connected directly to an AC supply.... Unregulated....

Batteries wired in series 1 shy of AC supply voltage... ie. 9x12v = 108v for 120v AC... There will be tons of bubbling, heat, plate sluffage... and EXPLOSIVE GAS... 2-6 hours... remove... rest... auto charge individually... rest... test.... about a 50% success rate....

AGAIN.... Do not do this if you are shy.... You or any body utilizing assumes all risk and liability....

[dennisail]

I tried to target a single dead cell on a battery once by jamming screwdrivers into the adjacent plates and hooking a high power charger to that cell only. I should have turned it off before I put the alligator clamps on the screwdrivers.

The resulting explosion was pretty bad and I was covered in acid. Nothing a quick shower couldn't fix, although the clothes I was wearing ended up full of holes.

So yeah, be careful.

[laforge24]

I am sure you mean well giving this type of advice

But these batteries have a life span of over 15 years
and are still in pretty good condition
As one lives without grid electricity it is somewhat
difficult sometimes to get a hold of 110V which you want to
shortcut on your batteries without the fuses or generator to blow

they had been charging and bubling at 29.5V for 5hours
Now 24hours disconnected the voltage showed 24.9V
I think it has done them well
thanks for your input

[d design]

Battery: An electrochemical storage device capable of lighting an incandescent lamp of a wattage about equal to that of a refrigerator bulb for a period of 15 minutes after having been charged for 2 hours.

[noelex 77]

Originally Posted by dennisail

The resulting explosion was pretty bad and I was covered in acid. Nothing a quick shower couldn't fix, although the clothes I was wearing ended up full of holes.

Not enough people wear eye protection when working around batteries. Battery explosions are rare, but they produce bilateral injuries that are much more debilitating than the monocular injuries that are usually seen when metalworking etc.

To the OP's question.
This sort of battery can have a very long life so I agree it worth some effort to try and restore them, but any battery LA cell left at 2v for any length of time (or even worse 1.85v) will be damaged and may not recover any useful life.

It is much better to charge and test the cells individually. This is going to be difficult to do with your limited equipment and lack of mains power. If you can borrow a lab power supply and feed it via an inverter linked to another battery fed from your solar panels it would be ideal.
I would consult the battery manufacturers and see what they recommend, but the normal procedure is an equalisation charge for a couple of hours at 2.5-2.6 volts per cell (assuming 20c).

[Nicholson58]

Handy Bob has some advice regarding de-sulphanization and charging of batteries that might help. Long read.

HandyBob's Blog « Making off grid RV electrical systems work