Hi Roy
On (20 Oct 96) Roy J. Tellason wrote to Alec Cameron...
 AC> I found it helpful to use an extremely high source voltage of 
 AC> [memory] maybe 20 volts/ cell BUT with a lot of series 
 AC> resistance, to protect the cells [and charger] if and when the 
 AC> cell v locked in to the normal range 2.0> 2.6 volts. 
 RJ> When I ran that battery store,  there were times when I'd get a unit 
which
 RJ> wasn't responding and I'd stick it on a series charger and crank it 
way*
 RJ> up there,  usually with my DVM in series to see when current started to
 RJ> flow,  then I'd back it off significantly.
Maybe you remember the old Tungar chargers- these were a 1/2 wave setup, a
glass tube mercury diode the size of a 150 watt lamp having a plate lead at 
top
and a GES base to supply the heater at about 2v 25amps. These were the common
service station charger, and a variable number of batteries would be series
connected with the cell caps removed. No adjustments as the tranny had enough
reactance that a constant 6 amps would flow for the range 2volts up to about 
80
volts.
 AC> So at the beginning of the "charge" the cell terminals were 
 AC> reading very high [over 5v/cell]. As the hours/ days passed, 
 AC> with an input current of about C/30 the cell v dropped back to 
 AC> about 2.2, slowly increasing to a conventional value of about 
 AC> 2.4. When the volts stabilised, I discharged the cells and then 
 AC> gave a normal recharge and got OK service thereafter. Probably 
 AC> for a couple of years, in float service, burglar alarm system.
 RJ> Why discharge them and re-do it?  I've had to push some to "wake 'em 
p",
 RJ> but never did that with them...
Discharge/ recharge is a works remedy for increasing the stored energy. It
works. When we used to factory- test a new battery for customer Inspector
approval, a poor result [eg 3000 amp hours guaranteed but only 2600 achieved]
then one or two cycles of recharge discharge would bring the battery up to
spec. But at some cost-
        * Delivery delay of a couple of days, costly in big business.
        * Cost of kwH charging energy, and test bay labour required.
        * Corrosion of the plates and immersed connections, ie a marginal 
oss
        of battery durability.
Why does it work? I think that the first  charge cycle is incomplete
because the active material hasn't "bedded" neatly into the plate pockets, 
nd
maybe there are some harmless but inhibiting substances [impurities] that
need to be persuaded to move along and the cycles of charge help. BUT some
[not much] of the stored energy is provided by surface conversion of the
lead/ lead alloy structures of the plates framework and submerged bus
connectors. These surfaces probably become deeper and more porous with cycles
[re flush and refill.......
 RJ> I've heard of people trying this,  but would tend to think that the
 RJ> separators between the plates would tend to trap any of that material 
that
 RJ> was stuck under the plates,  so I don't know how successful it'd be.  
I've
 RJ> never felt ambitious enough to want to try it myself.
I have only had one really good success, that was a 12v acid battery. I have
had failures too ie the duds stayed dud.  Cheers....ALEC
... FLASH! Energiser bunny arrested, charged with battery.
--- PPoint 1.92
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