[TechAssist] Re: Any way to revitalize dead sealed lead acid batteries?

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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