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NiCads

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alexpeterson(at)earthlink
Guest

Posted: Sun Mar 19, 2006 6:17 pm Post subject: NiCads

Years ago, I knew an electrical engineer who claimed he could rejuvenate

NiCad batteries by charging a capacitor and zapping it across the battery.

I watched him do this, and saw what I recall were positive results. He

claimed it reduced the internal resistance, so they would hold a charge

better.  Is there anything to this?

 



Alex Peterson

RV6-A N66AP 729 hours

Maple Grove, MN

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rv-9a-online(at)telus.net
Guest

Posted: Sun Mar 19, 2006 6:50 pm Post subject: NiCads

I've done it a lot.  I used it to blow out internal shorts in battery 

packs.  I'd take a big computer-grade low esr electrolytic, charge it 

with a power supply then connect it to the batter pack.



The large current would blow out any internal shorts.



This works a few times, but is not a permanent fix for NiCd problems.



Also, the charge rate of NiCd batteries is proportional to the discharge 

rate... so the trick is to discharge them quickly, then charge them 

quickly using special chargers (battery charger/conditioners).



Also, it's better to pulse charge the NiCd batteries, rather than using 

a smooth DC charging source.



You may want to Google it, because there is a lot of info available.



Vern Little



Alex Peterson wrote:

 	  Quote: 	
		   

 

 Years ago, I knew an electrical engineer who claimed he could rejuvenate

 NiCad batteries by charging a capacitor and zapping it across the battery.

 I watched him do this, and saw what I recall were positive results. He

 claimed it reduced the internal resistance, so they would hold a charge

 better.  Is there anything to this?

  

 

 Alex Peterson

 RV6-A N66AP 729 hours

 Maple Grove, MN

- The Matronics AeroElectric-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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brian

Joined: 02 Jan 2006
Posts: 643
Location: Sacramento, California, USA

Posted: Sun Mar 19, 2006 7:18 pm Post subject: NiCads

Alex Peterson wrote:

 	  Quote: 	
		   

 

 Years ago, I knew an electrical engineer who claimed he could rejuvenate

 NiCad batteries by charging a capacitor and zapping it across the battery.

 I watched him do this, and saw what I recall were positive results. He

 claimed it reduced the internal resistance, so they would hold a charge

 better.  Is there anything to this?


	


There is something to this but it is not because it reduced the internal 

resistance.



Seems that NiCds have a tendency for the sodium hydroxide electrolyte to 

form conductive crystals if the battery is left discharged. The crystals 

grow through the separator and cause a short between the plates 

(electrodes inside the battery). When that happens you can't charge the 

NiCd.



What the capacitor does is provide a huge momentary current that 

destroys these crystals without overheating the battery. Once the shorts 

are blown clear, the battery will then take a charge.



The only caveat is, when this happens it usually means that the battery 

is approaching the end of its life. The crystal is not completely 

destroyed but the short is removed. The crystal is likely to grow back 

and short the cell again. Still, it is a useful technique if you need to 

get a couple more cycles from your NiCds.



-- 

Brian Lloyd                         361 Catterline Way

brian-yak at lloyd dot com          Folsom, CA 95630

+1.916.367.2131 (voice)             +1.270.912.0788 (fax)



I fly because it releases my mind from the tyranny of petty things . . .

- Antoine de Saint-Exupery

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_________________
Brian Lloyd
brian-yak at lloyd dot com
+1.916.367.2131 (voice) +1.270.912.0788 (fax)

I fly because it releases my mind from the tyranny of petty things . . .
- Antoine de Saint-Exupery

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