Anyway to resurrect some NiMH Cells - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 4th May 2008, 02:59 PM   #1
kvk is offline kvk  United States
diyAudio Member
 
Join Date: Jan 2008
Default Anyway to resurrect some NiMH Cells

I have some NiMH AA cells that are a few years old. Most of them charge but about 1/2 dozen don't. I put them in the smart charger and the light goes red (meaning charging) for about 10-20 seconds. Then the light goes out (which means the charger doesn't like the cell; not sure why, maybe no current runs through it?). For the good cells, then charge for 12-16 hours and then go green.

Anyway to poke these back to health? Maybe give them a little jolt or something like that?
  Reply With Quote
Old 4th May 2008, 03:25 PM   #2
diyAudio Member
 
purplepeople's Avatar
 
Join Date: Mar 2003
Location: London, Ontario, Canada
After about a year and half of not using them, a jolt is exactly how I brought some dead NiMH cells back to life, after reading about it a number of times on the web.

Warning... the following procedure is contrary to all manufacturers recommendations and may result in explosion or other danger. Anyone trying this accepts all responsibility for any property damage, injury or death that may result. Should you attempt this, use safety equipment, including goggles, gloves, grounded wrist strap, etc.

That said, using a 12V 1A adapter (transformer), I zapped each 1.5V cell positive to positive (and neg to neg) for as short a time as I could muster with my pliers. There will be a small spark. Wait some time before applying the normal charging routine. Et voila! Working cells. I have no idea how much charge is held vs. new, but they all take and hold a charge.

Good luck.

:)ensen.
__________________
Those who claim to be making history are often the same ones repeating it.
  Reply With Quote
Old 4th May 2008, 03:34 PM   #3
Ron E is offline Ron E  United States
diyAudio Member
 
Ron E's Avatar
 
Join Date: Jun 2002
Location: USA, MN
measure the voltage - I seem to recall that if REALLY discharged, they reverse polarity. They may be unrecoverable, or might only last half as long or less than normal and put stress on the better cells you might mix them with and accelerating damage to the poorer cell. Sort of like a spreading cancer.

I would just replace them. If it is significant money, try putting them on a non-smart slow charger, they might come partially back, or they might start a fire or something...

your mileage may vary, I am not a battery expert.
__________________
Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan
Armaments, universal debt, and planned obsolescence--those are the three pillars of Western prosperity. Aldous Huxley
  Reply With Quote
Old 4th May 2008, 03:39 PM   #4
Coulomb is offline Coulomb  England
diyAudio Member
 
Coulomb's Avatar
 
Join Date: Jul 2002
Location: Ancaster, Ontario
Actually what works really well and a lot safer than using an Arc welder to jump start them is, put them in a freezer baggie and throw them in the freezer overnight.

NiMH develop crystaline shorts overtime which reduce the battery capacity and "fool" the charger into thinking it is fully charged.

After removing from the freezer let the battery "thaw" for 12 hours, wipe off any condensation and recharge. I have rarley had this fail to bring back a NiMH. I do not usually bother with this process unless it is a custom pack size.

I have a Romba vaccum and after many recharges the "special" read really expensive, pack stopped recharging. One treatement and it has benn working good as new for several months now.

Eventually, like everything else, it will have to be replaced.

Anthony
__________________
I like to stay current!
  Reply With Quote
Old 7th May 2008, 04:03 PM   #5
soongsc is offline soongsc  Taiwan
diyAudio Member
 
soongsc's Avatar
 
Join Date: Mar 2005
Location: Taiwan
Quote:
Originally posted by Coulomb
Actually what works really well and a lot safer than using an Arc welder to jump start them is, put them in a freezer baggie and throw them in the freezer overnight.

NiMH develop crystaline shorts overtime which reduce the battery capacity and "fool" the charger into thinking it is fully charged.

After removing from the freezer let the battery "thaw" for 12 hours, wipe off any condensation and recharge. I have rarley had this fail to bring back a NiMH. I do not usually bother with this process unless it is a custom pack size.

I have a Romba vaccum and after many recharges the "special" read really expensive, pack stopped recharging. One treatement and it has benn working good as new for several months now.

Eventually, like everything else, it will have to be replaced.

Anthony
Is using a freezer baggie necessary?
I tried some ordinary NiMH batteries, threw them in the freezer without the baggie, and let them sit out for 12 hours after that. Some will charge, but somehow they either never get full or cannot deliver power when the charger says it's fully charged.
__________________
Hear the real thing!
  Reply With Quote
Old 7th May 2008, 07:52 PM   #6
Coulomb is offline Coulomb  England
diyAudio Member
 
Coulomb's Avatar
 
Join Date: Jul 2002
Location: Ancaster, Ontario
Baggie is just to keep moisture of the surface.

It is possible that the batteries are just to far gone.

Anthony
__________________
I like to stay current!
  Reply With Quote
Old 8th May 2008, 06:40 AM   #7
TroelsM is offline TroelsM  Denmark
diyAudio Member
 
TroelsM's Avatar
 
Join Date: May 2003
Location: AARHUS. DK
Hi

Will the freezer-method work with NiCd also?

Regards TroelsM
__________________
Need more time...
  Reply With Quote
Old 8th May 2008, 05:21 PM   #8
diyAudio Member
 
unclejed613's Avatar
 
Join Date: Dec 2006
Ni-Cd cells short out. best way to rejuv these is to take a large cap charged to 12V and discharge (observing proper polarity) across the shorted cell. this removes any Ni "needles" from between the electrodes. then you do several charge-discharge cycles to full voltage and discharging through a low resistance (to generate heat inside the battery and remove battery "memory"). the battery, while not as good as new, will at least be useable. the charge-discharge trick works also for sulfated gel-cell batteries as long as they're not too far gone.
__________________
Vintage Audio and Pro-Audio repair ampz(removethis)@sohonet.net
spammer trap: spammers must die
  Reply With Quote
Old 8th May 2008, 05:48 PM   #9
diyAudio Member
 
7n7is's Avatar
 
Join Date: Mar 2006
Location: VA
6566844
6504344
6469473
6441584
5998968
5698961
5493196
20080079397

http://www.pat2pdf.org
  Reply With Quote
Old 8th May 2008, 06:13 PM   #10
soongsc is offline soongsc  Taiwan
diyAudio Member
 
soongsc's Avatar
 
Join Date: Mar 2005
Location: Taiwan
Quote:
Originally posted by unclejed613
Ni-Cd cells short out. best way to rejuv these is to take a large cap charged to 12V and discharge (observing proper polarity) across the shorted cell. this removes any Ni "needles" from between the electrodes. then you do several charge-discharge cycles to full voltage and discharging through a low resistance (to generate heat inside the battery and remove battery "memory"). the battery, while not as good as new, will at least be useable. the charge-discharge trick works also for sulfated gel-cell batteries as long as they're not too far gone.
I used to open up my power amp, charge a cap with 70+ voltes, and the discharge it though the NiCd battery, works 90% of the time.
__________________
Hear the real thing!
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Need to resurrect my HK Citation 22... Jim K Solid State 25 19th December 2013 06:09 PM
9V from 2 AA cells space-cake Parts 6 7th October 2006 03:05 PM
who makes cyclon cells? Clipped Parts 6 1st April 2006 03:03 PM
How to make Fuel cells ?? jacquesl Everything Else 8 24th March 2005 07:53 PM


New To Site? Need Help?

All times are GMT. The time now is 11:54 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2