[TechAssist] Re: Any way to revitalize dead sealed lead acid batteries?
- From: Jim Shupe <jim@xxxxxxxxxxxxx>
- To: techassist@xxxxxxxxxxxxx
- Date: Tue, 31 Aug 2004 05:56:40 -0700 (PDT)
Gary..
You can get pretty carried away playing with
rechargeable batteries. I've been fascinated by them
since I was a kid... at 10 the thing I wanted most was
an old car battery.
In the eighties, I designed a "cycler" to
automatically take the battery to full-charge, then
discharge to nominal (9.6V, if I remember correctly)
to maintain battery chemistry and capacity. I can't
remember the number of cycles, but half a dozen or so
would be plenty, I'm sure. Rechargeables are like the
body...use it or lose it! Once the cells are
sulphated, the plates can actually be physically
damaged by the formation of large crystals and
short..I always look for battery voltages lower by
cell voltage multiples (2.2V for lead-acid) as an
indicator of shorted cells. I've never been successful
clearing a shorted lead-acid cell.
People will tell you different things about
batteries, especially how to charge them.I always
charge lead-acid with constant voltage(2.35V per cell)
and no current limit.
Have fun..
Jim Shupe, CET
Lloyd's TV
Yucca Valley, CA
--- Gary McCartney <gary@xxxxxxxxxxx> wrote:
> Jim, thanks for the suggestion. So far I have tried
> the reverse charging
> on one battery. Here is what my observations are:
>
> -initial battery read 4.1V and would not supply
> current to a load
> -reversed charged for several seconds but would not
> draw more than 100mA
> during this time.
> -then normal charged where it would only draw a few
> 100mA. Got up to
> 7.3V after a few hours and wouldn't supply current
> to load
> -reversed charged again and this time it drew around
> 200 mA
> - normal charging would now draw 100mA but still
> wouldn't supply much
> current to a load. A small lamp lit dimly for 5
> minutes and went out.
> -repeating the reverse charge- normal charge cycles
> seems to allow more
> current to be drawn each time.
> - last I tried, I was able to draw over 1 amp
> reverse charge and 200 mA
> normal charge. Battery reads 9.4V after a few hours
> charge but won't
> supply much current. I will attempt this on another
> battery to see if it
> reacts the same as the first battery. I will also
> try to reverse charge
> for a longer time period, such as a full minute.
> Will post another
> update on the experiment.
>
>
>
>
> Gary McCartney
>
> McCartney Electronics
> Guelph Ontario Canada
> Est. 1984
> email: gary (at) number63.ca
>
>
>
>
>
>
>
> Jim Shupe wrote:
> > Gary...
> >
> > Try reverse-charging (limit current to an amp or
> > less) for a few seconds to a minute to get things
> > going, then forward-charge at no more than 14.75V
> > until the current drops below about 100ma. If this
> > restores some charge to the battery, put it
> through
> > several normal charge-discharge cycles to achieve
> the
> > best capacity for THIS particular battery(I assign
> > batteries a "personality", unique to each one's
> > "experiences").
> > If not much happens the first time, repeat
> several
> > times before giving up. In my experience, it
> depends a
> > lot on the brand and storage conditions(the cooler
> the
> > better).
> > I used to manage storage, maintenance and
> testing of
> > gel-cell batteries as a test engineer for a
> medical
> > equipment manufacturer, so I experimented with and
> > researched a lot of this stuff.
> >
> > Batteries are still a long way from a reliable
> > device. BTW...somewhere I have a schematic for a
> very
> > good, simple two-stage gel-cell charger if you
> need
> > one.
> >
> > Jim Shupe, CET
> > Lloyd's TV
> > Yucca Valley, CA
> >
> > --- Gary McCartney <gary@xxxxxxxxxxx> wrote:
> >
> >
> >>I found a box of 10 brand new sealed lead acid
> >>batteries, 12V 4AH that I
> >>forgot I had. Problem is, they are all very low or
> >>dead. I tried
> >>connecting my power supply with current limiting
> but
> >>the batteries
> >>aren't drawing any current at all.
> >>
> >>Is there any way to kick these into charging up,
> or
> >>are they garbage?
> >>--
> >>
> >>
> >>
> >>
> >>Gary McCartney
> >>
> >>McCartney Electronics
> >>Guelph Ontario Canada
> >>Est. 1984
> >>email: gary (at) number63.ca
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >
> >
>
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