[NSRCA-discussion] NiMH follow up

[Ed Alt]

Dean:
Those sound like the best NiMh's to buy in that case.  Never tried them myself.  SR does cell matching and so forth as I recall.  Maybe some conditioning happens as they go through that process?  Anyways, being able to reliably do a C/2 charge on a NiMh is really good.  I don't think I was ever successful on reliably going higher than C/4 with the packs I was running.  This was with the Alpha 4.

Ed
  ----- Original Message ----- 
  From: Dean Pappas 
  To: NSRCA Mailing List 
  Sent: Monday, February 27, 2006 10:16 AM
  Subject: Re: [NSRCA-discussion] NiMH follow up


  Aha!
  Hi Ed,
  The "good" low resistance NiMh cells don't need a couple of conditioning cycles to come to full capacity. I confirmed this with both Larry at SR Batteries, and with Steve at NoBS Batteries.
  Both sets of  900H cells that I bought several months ago, checked within 1% of their best capacity after the first cycle. I was told that is normal, and to still stick to a max C/2 fast charge.

  Dean

  Dean Pappas 
  Sr. Design Engineer 
  Kodeos Communications 
  111 Corporate Blvd. 
  South Plainfield, N.J. 07080 
  (908) 222-7817 phone 
  (908) 222-2392 fax 
  d.pappas at kodeos.com 

    -----Original Message-----
    From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Ed Alt
    Sent: Monday, February 27, 2006 6:40 AM
    To: NSRCA Mailing List
    Subject: Re: [NSRCA-discussion] NiMH follow up


    Ed:
    Yep, 1/10C would be 220 mA for your 2200 mAh pack.  To condition a NiMh pack when brand new, you do several conditioning charges at 1/10C.  You want to go a full 24 hours at 1/10C, do a discharge to complete a cycle and repeat for a total of 3 or 4 full cycles.  This will generally get you to full capacity and also gets the cells ready to accept higher rate charging and with the right charger, they will then start to give a reliable indication of when they have peaked.  After these first conditioning charges, you do not want to exceed about 16 hrs at 1/10C, though at 1/10C it's a low enough rate that you're not going to damage it if you do go over.  Anything higher than 1/10C can shorten the life of the cells if repeated overcharging is done.  The higher the rate and the more time it is overcharged, the faster the degradation can occur.

    Ed


      ----- Original Message ----- 
      From: Ed Deaver 
      To: NSRCA Mailing List 
      Sent: Monday, February 27, 2006 12:57 AM
      Subject: Re: [NSRCA-discussion] NiMH follow up


      OK, for us non-electical whiz bang guys, please explain the C charge.  I have heard it before and tried what was suggested on RCU without success.

      My new NmHD pack is a 2200mah, 4 cell pack.  To condiditon it properly for first flights what should I do?  

      Does 1/10 C mean charge at 220 mah for 16 hrs??

      THanx for the explanation.

      ed

      Michael Cohen <precisionaero at comcast.net> wrote:
        Thanks to those who helped me with the advice. The 1/10 C change was the 
        answer. Both packs are happily at 1610-1690 capacity for their 1650 rating. 
        I also visited an old friend's website, Electrodynamics in Michigan. They 
        had an interesting write up on their website about NiCD (with a little NiMH 
        sprinkled in! ). I used to buy all my switches, extensions, and battery packs 
        from them when I lived in the Great White North. Their advice was 1/10 C 
        also, but they had lots of other good info there as well. I recommend you 
        take a look, unless your one of those Lithium people.

        Mike Cohen 


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