AC> Hi Roy
Hi.
 AC> On (13 Oct 96) Roy J. Tellason wrote to Alec Cameron...
 RJ> I've acquired,  recently,  about a dozen or so gel batteries,  eight of
 RJ> them 33 AH units and the other four 10 AH units.  Mostly I've been busy
 RJ> dumping some charge into them...
 RJ> I'm told that the reason they were being disposed of is that they sat on
 RJ> the shelf for too long.  With only one exception,  the seem to be 
howing
 RJ> me good voltage,  though.
 RJ> The part that bothers me about it is the idea of connecting all of these
 RJ> in parallel,  I keep thinking that there ought to be a better way.
 AC> I have only a little gel experience, which was with "sick" 
 AC> units and I agree that charging in parallel is NOT the way to 
 AC> refresh these if they've gotten ill.
Actually I wasn't considering charging them all in parallel,  though it 
probably *would* be quicker...   
I was thinking more along the lines of a setup where I would use / maintain 
them,  and although I've seen some (usually Diesel) vehicles that tied two or 
more units together,  I don't care for the idea of doing this with a bunch of 
gels like that.  I still haven't figured out a good way to set things up,  
though.
 AC> The sick ones I refreshed, were probably sulphated or otherwise 
 AC> highly resistive. At 2.5v/ cell DC applied from a charger, 
 AC> there was just NO significant current flow even tho the cells' 
 AC> open circuit voltage was way under 2.0.
I've seen that kind of thing happen too.
 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. 
When I ran that battery store,  there were times when I'd get a unit which 
wasn't responding and I'd stick it on a series charger and crank it *way* up 
there,  usually with my DVM in series to see when current started to flow,  
then I'd back it off significantly.
I got around to the one unit which was showing me 10 volts and change on the 
voltmeter earlier today,  and at first there was around a milliamp and change 
flowing,  and this kept on climbing until a while back it peaked at around 
700 mA or so.  Right now it's settled down to about 500 or so,  though these 
do tend to fluctuate a bit.
What I'm using for a "charger" is a little power supply box that I built 
which consists of a 4 amp bridge rectifier, filter caps,  and a salvaged 
transformer that I would guess based on size is capable of maybe 1.2 - 1.5 A 
output at most.  Unregulated,  this thing puts out around 16-18 volts at no 
load.  I've been pushing the 33 AH units until the charge rate dropped below 
0.25 A or so, stopping there so I could get to all of them.  Right now I'm on 
number 10 out of 12.
 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.
Why discharge them and re-do it?  I've had to push some to "wake 'em up", but 
never did that with them...
 AC> The initial "recharge" at about 20v/ cell limited by resistor 
 AC> to C/30 rate, was probably a depolarising and sulphate removal 
 AC> process NOT a conversion of active material from a discharged 
 AC> to a recharged condition. Once the cell volts had fallen down 
 AC> to 2.2 then I reckon the charging commenced.
One of these days I'm going to have to rig some kind of a setup where I can 
put a monitor on the voltage and watch the current at the same time...
Now that I've got these,  I have a number of batteries to play with,  so I 
can experiment a bit!    :-)
 AC> The maker name was Gates. Yuasa gel batteries I have used, I 
 AC> have had no trouble with at all, maybe because I sold the 
 AC> vehicles so equipped, before battery disorders occurred.
 AC> If you have a 6 cell battery reading 10 volts, and if it 
 AC> accepts a decent charge current from a 12/14v source but 
 AC> refuses to get up from 10 volts then you probably have a 
 AC> shorted cell. 
When I saw that low voltage,  this possibility occurred to me.  However I 
figured I'd see what happened after I tried to put some charge in it.  The 
initial reaction of *very* low current gave me the impression that it was 
just that far run down.
 AC> If a gel battery, chuck it out. If it is a liquid filled one 
 AC> then with rubber gloves and eye protection you might be able to 
 AC> dislodge the piece of gunk by draining the battery and flush it 
 AC> out with the garden hose, giving it a lot of bumping while 
 AC> inverted. Let the battery drain thoroughly after, because the 
 AC> water you flushed with ain't distilled. Refill with proper 
 AC> electrolyte [you can reuse what you took out, it doesn't 
 AC> deteriorate] and re charge. You might be lucky!
I've heard of people trying this,  but would tend to think that the 
separators between the plates would tend to trap any of that material that 
was stuck under the plates,  so I don't know how successful it'd be.  I've 
never felt ambitious enough to want to try it myself.
 AC> If you do this in the bath tub then wait till Someone has
 AC> gone out shopping!! 

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