[NSRCA-discussion] NiMH follow up

[John Ferrell]

You have to compensate for losses. Very few things electrical work at better than 80% efficiency and most are better than 50%. 17 hours seems to be a popular guess. 10 hours will not do it, 17 will always fill it up if it will fill up based on most people's experience. 

John Ferrell    
http://DixieNC.US

  ----- Original Message ----- 
  From: George Kennie 
  To: NSRCA Mailing List 
  Sent: Tuesday, February 28, 2006 10:29 AM
  Subject: Re: [NSRCA-discussion] NiMH follow up


  Hi John, 
  Thanks for the kind words, but I have the same struggles grasping some of this stuff as anybody else (probably quite a bit more). Take this battery stuff. I can't understand why it is that if I take my 500 ma pak and connect it to my 50 ma wall charger for 10 hours it isn't fully charged?????  Why is it necessary to charge it for 16 hours and try to stuff 800 ma into that little package (hmmm,......maybe that's why those lipos swell up that way??? BG ). I'm aware that when I fast charge my Tx pak, if I can get it off the charger about 3-5 minutes before that buggar reaches peak, the voltage will read 12 volts, but if I leave it on past peak the voltage will be depressed to 11.4 or even 11.2. So why the heck would we want to charge for 16 hours when the max voltage probably occurs somewhere around 10 hours?????????(I'm guessing). 
  You and Ed have a really good handle on this stuff, but I don't !!!! 
  Georgie 
    
  John Pavlick wrote: 

     Jay, Yeah, I guess I forgot to point that out. The time applies to a fully discharged pack (.9 ~ 1V  per cell). At C/10 it's pretty hard to hurt anything by "overcharging" i.e. charge a partially discharged pack for 16 hours. At the higher rates it becomes a very real possibility. Normally for "Fast" charging you'd use a good Peak detect charger: 0 delta V  or negative delta V depending on the cell chemistry. For C/10 you can get away with a low cost constant current charger - but you do need to shut it off! Ed also pointed out that new packs generally need a full 20 hours on the charger at C/10. I would agree that this is a good thing to do, but do remember to stop charging them at 20 hours. It's easy to forget. Better yet use a timer, but if you go this route, make sure that the charger won't turn into a "discharger" when the input power is removed. 
    John Pavlick 
    http://www.idseng.com  

      -----Original Message----- 
      From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Jay Marshall 
      Sent: Tuesday, February 28, 2006 4:23 PM 
      To: NSRCA Mailing List 
      Subject: Re: [NSRCA-discussion] NiMH follow up
      You are correct on the rate. The time is dependatn upon how much of the original charge remains. A good charger will charge only as long as necessary to meet its full chare specification (voltage, etc.).
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