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Gareth

Flashing a NiCad battery

Has anyone ever done this ?

I have 7 Ryobi 18 volt one plus batteries that have started to not hold charge. OK, they are between 3 and 3 & 1/2 years old now, and have been charged and duty cycle discharged many times, but over the last few days and this colder weather I have notice a significant degradation in them.

I understand that most of the problems with deteriorating Ni-Cads are usually caused by crystallization inside the battery, and that zapping them with twice the normal voltage can sort out this problem out ... .... have any of you tried this? I thought I'd ask, before embarking upon this one.

I found this video on Instructables: http://www.instructables.com/id/R...tteries-by-Zapping-with-a-Welder/
kaz

Sounds risky Gareth
Justme

You might also want to check out the internal condition of the battery pack. My last drills battery pack had started to rust the internal cell inter links.
milton

Gareth, you need current rather than voltage to burn off the Cadmium whiskers that form. Car battery is as good as anything because you get a big inrush.

Jump leads on the car battery, then on to your NiCad for a couple of seconds. If it's a battery pack you need to get to the individual cells or the current inrush will just dissipate before it does anything.

They can explode if you hold the jumpleads on too long, so be careful, protect yourself and all that.

You do this at your own risk  
Gareth

Discretion is the better part of valour; so I am going to initially try another method to see if that works first.

I am going to seal individual batteries in plastic bags and then freeze them for a few days. If that doesn't work, then it's out with the electric welder and face mask to flash them.

I striped a battery down yesterday so that I could establish which terminal is which; there are three terminals on a Ryobi one-plus battery; a positive, negative and sensor. Not so easily done with a fully assembled battery as two of the terminals were giving voltage outputs, but now I know which one is the sensor, I think that I can safely flash these batteries.
Justme

Dont flash them at the bats. Make a fixed connection at the bat & do the flashing remotely just in case.
Gareth

Justme wrote:
Dont flash them at the bats. Make a fixed connection at the bat & do the flashing remotely just in case.


Flashing the batteries remotely will be my only option if the deep freeze doesn't work.  I have a 5 metre length of 6mm 3 phase cable which I can use. If I then run this to the battery covered by a plastic builders bucket and then a plastic garden trug, and then flash from behind my steel & plywood covered bench,  I think that I'll be safe enough.
Woodsmoke

Don't forget your hat..........................

Justme

Lol.

I have two bats. One has 18.6kwh & the other 33.6kwh of stored energy. I think even your steel bench would not protect you if one of them was shorted out.


EEK just thinking about that makes me want to site them just a little bit further away than they are.
Gareth

Back in 1979 when I was a raw apprentice for R Cripps, a 75 amp/h, 643 tractor battery that was on charge in the bay next to mine went up. The resulting casing shrapnel completely missed me, but I was covered head to toe in electrolyte. The dark navy blue overalls I was wearing turned a pinky purple colour and my foreman used the fire hose to hose me down .... .... ... and I got away without mark on me.

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