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G7HJQ > TECHNI 20.04.07 09:14l 60 Lines 3181 Bytes #999 (0) @ WW
BID : CB0195G7HJQ
Read: GUEST OE7FMI
Subj: Lead Acid battery recovery.
Path: DB0FHN<DB0FOR<DB0MRW<OK0PPL<DB0RES<TU5EX<F6BZU<F5GOV<CX2SA<N9PMO<
GB7LDI<GB7HOL<GB7IMK<GB7CIP<GB7IPW<GB7FCR
Sent: 070419/1642Z @:GB7FCR.#16.GBR.EU #:27562 [Blackpool] FBB-7.03a $:CB0195G7
From: G7HJQ@GB7FCR.#16.GBR.EU
To : TECHNI@GBR
Hi All,
Having read several useful Bull's from G8MNY on the
recovery of batteries, and having purchased from a car boot sale a
portable 12V battery pack for jump starting car's in an emergency, I
thought I would have a go at recovering the battery.
The following notes are my personal observations on
doing this recovery, which in my case was fully successful.
Having made certain the battery was fully discharged,
after finding out that it would not take a charge, I connected it to
a PSU with a variable voltage and a variable fixed current limit and
processed to reverse charge it, with the PSU set at 13.5 and at a
maximum current of 4 amps.
The battery took the reverse charge and so after three
or four minutes, I disconnected it, checked that no high reverse output
was present and proceeded to charge it in the normal direction.
The battery started to take the charge and so I left
it on charge. After a couple of hours the charging current had dropped
right back, indicating that the battery was only taking a part charge.
I disconnected the battery from the charger and fully
discharged it, checking with a shorting lead that it was fully
discharged. Then I proceeded to reverse charge it again, but this time
I set the output voltage to 2.2 volts, at a current of 4 amps.
The battery proceeded to take a reverse charge at this
setting for about 5 to 10 minutes and then stopped taking the reverse
charge. I then increased the output voltage from the PSU to 4.4 volts,
again at the same current setting. After a further 5 to 10 minutes,
again the battery stopped taking the reverse charge. Yet again, I
increased the PSU output voltage by 2.2 volts, again the battery started
to take the reverse charge for about 5 to 10 minutes.
This made me think and then the penny dropped, the
battery stopped reverse charging each time a cell came up. With this in
mind, I continued to increase the voltage each time the battery stopped
taking a charge, until I had done it for the 6 cells in the battery, it
being a 12 volt battery.
I then disconnected the battery and then began once
again to charge it in a normal manner. With the battery being reverse
charged it had become warm and so as not to over heat the battery and
possibly cause any lasting damage to the cell plates, I limited the
charge current to 1 amp at 13.5 volts until the battery cooled off and
then increased it up to 4 amps.
The battery took a full charge and I have tested it
with a battery drop tester and it is holding it's charge and supplying
the correct current.
The above procedure was done nearly two weeks ago and
the battery is still holding it's charge and stands up to a drop test
to check on the capacity.
The procedure I have listed worked in my case, but
will ultimately depend on how badly the battery has deteriorated and that
it has not been left without electrolyte.
Why not give it a try, if you use the correct equipment,
in the correct manner, then you have nothing to loose and possibly you
you will regain a working battery.
Mike Erber G7HJQ, April 19th 2007
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