From: adam@address.invalid   
      
   Robert Riches wrote:   
   > On 2012-07-03, Aragorn  wrote:   
   >> On Tuesday 03 July 2012 04:22, Adam conveyed the following to   
   >> alt.os.linux.mandriva...   
   >>> I read that Li-ion batteries, unlike   
   >>> NiCd/NiMH, should /not/ be allowed to discharge completely if   
   >>> possible.   
   >>   
   >> No, that is not correct.  NiCd batteries _must_ be periodically   
   >> discharged completely   
   >   
   > Yes and no.   
      
   Thanks for the detailed reply, Robert!  Does what you wrote apply   
   equally to the NiMh rechargeable batteries that have replaced NiCds in   
   the U.S.?   
      
   > NiCd cells must be discharged or they develop the memory   
   > effect   
      
   Isn't just leaving them alone for a few months effectively discharging   
   them?  I read somewhere that NiCds lose about 1% of their charge per day   
   when they're not used.   
      
   > However, if you fully discharge a series chain of cells (a   
   > battery of cells, aka a battery)   
      
   I assume that includes a "9V" rechargeable battery, which is 6 1.2V   
   cells in series (so actually 7.2V total).   
      
   > you run the risk of reverse   
   > charging the weakest cell in the chain.  Reverse charging a NiCd   
   > cell results in a dead short caused by metal whiskers inside the   
   > cell.   
      
   How does one detect that?  Will the cell actually have a negative voltage?   
      
   > The cure for such a shorted cell is to charge up a   
   > substantial electrolytic capacitor (at least a couple milliFarads   
   > aka a couple thousand microfarads) to around 12 Volts or more and   
   > _ZAP_ the cell in the positive polarity.   
      
   So the +ve terminal on the charged capacitor would go to the +ve   
   terminal on the battery?  For how long?   
      
   > The only problem with the zap cure is it reduces the capacity of   
   > the cell slightly, and it was already the weakest cell in the   
   > chain.  The weakest cell gets weaker.   
      
   And, I assume, eventually won't hold a charge at all.  Is that the same   
   thing as a NiCd cell failing (won't hold a charge, even when charged   
   separately) from normal use, after numerous charge/discharge cycles?   
      
   BTW do you have any comment on the "controversy" here about discharging   
   Li-ion batteries?   
      
   Adam   
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