🚀 go-pugleaf

<<<Now, can someone post similar guidelines for gel-cells?  I have one that 
self-discharges in about two weeks, and won't take a charging current over 100 
ma (it's a 5 ah battery) without exceeding 2.25 volts/cell.  Is it NFG?>>>

I inherited quite a number of these from the trash bin at a previous job, so 
I've had some experience reviving them.

Gel-cells, being of your basic lead-acid chemistry, are charged at a constant 
voltage, as opposed to the constant current used to change NiCd cells.  Maximum 
"trickle charge" voltage is 2.3 volts per cell -- gel-cells can safely 
dissipate an indefinite charge at this potential.  In addition, there is a 
"maximum bulk charge rate", which is typically .2C.  Extremely dead cells may 
go above this rate if fed from a 2.3V/cell charger.  Going above this rate will 
cause excessive outgassing, which will eventuall dry out the electrolyte.

When the electrolyte dries up, the cell develops a high impedance, refusing to 
accept much current at the 2.3V/cell potential.  To fix this situation, you 
need a drill press, a 1/4" to 3/8" bit, and a syringe.

Clamp the cell in the drill press vise, and set the stop in order to drill 
about 1/8" through the cover.  Be careful!  If you do not clamp the cell 
tightly, or do not set the stop properly, the bit will dig right into the cell, 
destroying the vent seal and possibly the whole cell!

Once you have a neat little hole in *just* the plastic cover, use a small nail 
or tack to poke a small hole in the rubber vent seal.  Fill the syringe with 
distilled water, insert the syringe into the vent seal hole, and add as much 
water to the cell as it will take.

****IMPORTANT****   ****WEAR EYE PROTECTION!****  If you have over filled the 
cell, fluid will squirt out when removing the syringe!  Tilt the syringe toward 
you, and have some acid-resitant (like polyethelyne) backdrop to avoid damaging 
your work area!

Using a constant-current source, charge the cells at a .1C rate.  THis may 
require as much as 20V/cell if the cell is extremely dry.  Check the fluid 
often, replenishing a s necessary.

When the cell voltage falls to about 2.5V/cell, switch to a constant voltage, 
2.3V/cell charge for about a week to absorb any free fluid left.  At the end of 
this period, remove any unabsorbed fluid with the syringe.  BE CAREFULE!  THIS 
IS BATTERY ACID!  DISPOSE OF PROPERLY!

If you damaged the vent seal during the drilling operation, you can touch up 
with silicone caulk.  Do not use too much, or the cell might develop excessive 
pressure during the outgassing that accompanies charging.

I've had great luck with this process, although I've destroyed a few cells in 
developing it.

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