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Proper charging of worn out lead-acid batteries

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Member level 3
Oct 28, 2010
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Hi! I know the standard way to cycle charge a battery: constant current at e.g. C/10 to C/4 until 2.40V per cell, keep that constant voltage until it drops to about C/100. And the hydrometer will show about 1280.
That's standard for brand new batteries. But what if the battery's capacity has fallen to 50% or less due to irreversible sulfation or active material loss? At the factory there is a forklift in this condition, my boss doesn't feel the need to change the expensive pack because its capacity is Ok for the little use that is given to the vehicle. But the charger causes the cells bubble long before reaching their present capacity, and the hydrometer stays in the red (discharged) zone.
This is my opinion: as the active surfaces diminish, there is less surface to convert the PbO2 into sulfuric acid, so one has to accept that the maximum achievable density naturally will be lower, and the same will be true for the voltage. So, cycle charging to 2.4V is an abuse and it should be set lower. But I couldn't find info on this.
Do you agree? Your answer will be worth a lot of money! Thank you!

From what I've read, some of the consequences of
sulfation are irreversible (plate damage). However I
have had occasional success with just leaving the
battery on a trickle charge and giving it a good
"sloshing" every time I walk by, over some weeks.

Have thought about trying to rig a "rocker plate" to
automate the agitation.

May want to experiment with violent electrical
methods, like slamming the posts with a high narrow
pulse meant to shake the plates capacitively, more
than transferring any charge. Or superimpose an
inductor-blocked DC feed and a pulse "rattler"....

Be sure and report any success....

Youtube full of restoration tips. Some drain all acid (saving it), flush out,
then restore acid. Some add a step of adding epsom salts to each cell. Some
use short term over charging to clear shorted cells.

I recently added epsom salts to a battery that was marginal, actually restored
it significantly. Next go around I will do the flush approach.

Regards, Dana.

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