Author Topic: Acupuncture for ailing NiCad paks  (Read 4664 times)

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Offline Norm

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Acupuncture for ailing NiCad paks
« on: May 24, 2012, 04:30:44 pm »
This is probably more for complete newbies on NiCads,
even those are probably aware of zapping NiCads in a group
but there is a better way....why zap the whole bunch when there is
maybe only one in a half dozen that needs to be zapped....also if
you can check each individual cell before they get too bad there is
hope that you can prolong the life of the whole bunch so here is what I
do ....checking each stack of this 12-13.7 NiCac pack ....most of them
were reading 6.50  a couple were only reading like 5.80  so I use small
brads for probes  and check each cell and find.....
1185-0
and like aha this one only reads .95......so I zap it just a couple of quick
touches with 12 volt battery charger clamps and we're back in business
after a slow charge to balance them all out.
Norm.

Offline bj

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Re: Acupuncture for ailing NiCad paks
« Reply #1 on: May 24, 2012, 05:00:59 pm »
   Have to admit Norm, I didn't know you could get away with that.  So, if I might ask, what's your
definition of a short zap?  I am assuming that too long a zap is not better.
   Thanks in advance
"Even a blind squirrel will find an acorn once in a while"
bj

Offline Wolvenar

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Re: Acupuncture for ailing NiCad paks
« Reply #2 on: May 24, 2012, 05:22:37 pm »
I had done this many years back on NiCad.
I really didn't know that this was a tried and true method to recover anything though.
I thought I just got lucky
Trying to make power from alternative energy any which way I can.
Just to abuse what I make. (and run this site)

Offline Norm

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Re: Acupuncture for ailing NiCad paks
« Reply #3 on: May 24, 2012, 08:22:22 pm »
   Have to admit Norm, I didn't know you could get away with that.  So, if I might ask, what's your
definition of a short zap?  I am assuming that too long a zap is not better.
   Thanks in advance
Well it's like accidentally shorting a battery and you say oh oops...oops...oops! a couple of times 12 volts instead of 2 or 3 volts to a nominal 1.2 volt battery is like you taking
110 volts.....you wouldn't zap yourself very long ....would you .....knocks the whiskers off
don't it ?
Usually a couple of short zaps does it, if the other 4 out of say 5 are reading 1.2 -1.3
and the one reads ....maybe .6 you might save it by zapping it about 2 or 3 times
real quick if it comes up to 1.2 , if not try once more, usually it might come up to the same as the others....if it loses it after a couple of minutes ....forget it and replace it, you can,
they're actually in a shrink wrap tube that you can slice open but retain their shape so you
can slip them back in the tube after you replace them and some tape over the cut.
While I'm not an expert  ...that's about all I do pedal and recharge and rejuvenate NiCads
any more questions ....just ask
Norm. 

Offline Norm

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Re: Acupuncture for ailing NiCad paks
« Reply #4 on: May 24, 2012, 08:32:43 pm »
I had done this many years back on NiCad.
I really didn't know that this was a tried and true method to recover anything though.
I thought I just got lucky
The big secret is to catch them before they get too bad
to check each one and zap every one that is just a little less than the others
that way they all get charged equally

Offline ghurd

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Re: Acupuncture for ailing NiCad paks
« Reply #5 on: June 04, 2012, 09:28:48 pm »
"So, if I might ask, what's your
definition of a short zap?"

My definition is like slapping 2 bare wires past each other that touch,
so they just make a spark... and not really "contact".

My fuzzy understanding of it is the 'whiskers' are
sort of like ultra-fine chemical structures that short the cells.
All that needs done is to pass enough current, long enough, to blow them like a fuse.
It takes voltage to do that, but a spark does it.

It works for me about half the time.
If 'newer' cell didn't sit around dead for too long, it has a decent success rate.
Older cells that are about used up, it can work but the sucess rate is lower and the AH is lower when it does work.
G-


Offline niall

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Re: Acupuncture for ailing NiCad paks
« Reply #6 on: July 03, 2013, 05:39:41 pm »
i had a go at the " zap" option Norm ....it seems to work on the cells i tried off an old battery pack that was almost finished ...(lack of use i think) ...i picked it up in the market

i tried recharging each cell individually but no luck ...the charger would auto stop saying full with only about 50 mAh gone into the cell, a lot of the cells behaved the same .....

after a few zaps on a 12 batt there was a good change....now the cells started holding charge
this one (no 3) is almost full ....its meant to be 1500 mAh , so even de rating it to 1000 is a good result for me



i needed a replacement cell for the glo plug starter on the model plane ....now i have lots  :)



test ....



even if these revived cells loose their charge a little quicker its not a problem as they will be used within a few hours of charging ....plus now i have plenty of them ....

(zapping is a bit unnerving though  :o)

ps...some of the cells didnt zap so good......they just fizzed a bit ....i didnt try recharging these ones ....maybe too far gone ?


 


   
 

Offline MadScientist267

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Re: Acupuncture for ailing NiCad paks
« Reply #7 on: July 03, 2013, 07:52:22 pm »
 Used to zap NiCd too, but had mixed results

They can take serious abuse, I don't think I've ever had one "go wrong"...

Biggest issue I've noticed is that the tendency is everything is ok until they get discharged to a certain point, and then the short recurs.

 Best results were with capacitive discharge, PC front end power supply caps are a decent cup of juice to dump into them. High current is the key in my experience with them. Car battery and jumper cables works halfway decent too, but not quite as well.

The current needs to be intense but short. Leaving it connected doesn't gain anything but heat in the cell. They're tough, but I'm sure they have their limits...

Of course, its not as simple as just yanking the screws out of that dead PC... Current limiting for the charging is a must, and should be set up so that it takes several seconds to reach full charge so that you can give it a controlled dose (the energy in the cap increases with voltage). The other challenge is switching... I used (and killed in short order) a relay, but solid state would be preferable to mechanical. Eventually, the contacts welded and the relay was shot. Didn't matter at the time, because the relay was free and it was experimental, but if I were to do it again, I'd ditch the relay in favor of silicon.

I also should point out for those that don't immediately see the danger here... We're talking anywhere from 100-320VDC, which at the very least will be extremely painful, and EASILY translates into lethal. Stay away from all of the high voltage wiring and battery. The use of  an interlock and a bleeder resistor is a must. You've been warned. :)

One other thing, while the chemistries are similar,  zapping isn't nearly as effective on NiMH as it is on NiCd. The shorts readily return.

FWIW...

Steve
Wanted: Schrödinger's cat, dead and alive.