[NSRCA-discussion] charging

Fri Aug 18 11:40:59 AKDT 2006

You can get away with a lot of things a few times....

The question is... can you get away with it all the time?

A few high rate charges succeeding means you can on an occasion get away with it.  Is it reducing the cycle life of the pack?  Not enough high charge rate cycles to know.  So even if it isn't a fire hazard (which it still might be...) it could be a bit expensive to do it.

I'll let the battery and charger makers do the experiments that might blow up.  They have the proper facilities (I hope) and the proper fire fighting equipment (I hope) and the properly trained personnel (I hope)

If you need a fresh charged LiPo for your model every 12 min... maybe having 5 or 6 packs and the ability to keep 4 on the charger at all times would do the job?  We know that works with reasonable safety.  There's even a charger designed for it. (for smaller packs...)
  ----- Original Message ----- 
  From: Dean Pappas 
  To: NSRCA Mailing List 
  Sent: Friday, August 18, 2006 1:59 PM
  Subject: Re: [NSRCA-discussion] charging

  Hi Georgie,
  What I remember the guys at that seminar said was something more like:
  If and only if:
  1) your charger balances continually and terminates charge if at any point it cannot maintain balance as the charge progresses,
  2) your battery is a high charge/discharge rate cell ( 15C or 20C rated)
  3) your charger terminates if for any reason any one cell hits 4.2V
  then you can charge at up to 3C
  Of course, the charger they were selling was built to satisfy #1 and #3. 
  Thunder-Power does something similar with a two-component system. 

  So you were charging at 5C with a standard 2-wire to the battery charger? Please be careful, my friend.

  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 george w. kennie
    Sent: Friday, August 18, 2006 2:00 PM
    To: NSRCA Mailing List
    Subject: [NSRCA-discussion] charging

    This is just an FYI based on my experience.
    At the WRAM Show I attended a seminar by the Kokam Battery guys and was advised that it would be completely safe to charge my Lithium Poly batteries at a rate of 3C if one was using one of their Balance Pro Chargers. Well, needless to say, I didn't purchase one of their chargers, however, after hearing about several others who were charging at 3C I decided that I would try the 3C rate and find out what my experience would be like.
    I have some small packs for foamies so I decided to try one of them expecting to find some negative result, but the opposite seemed to be the case. 
    A couple of weeks ago I attended a contest where I was shooting my mouth off about how I had been charging at 3C and was brought up short by one of those listening and advised that charging at this rate would cause the batteries to overheat, to which I responded rather emphatically that my batteries were remaining cool. This particular gentleman became rather insensed and insistant that he knew for a fact that the heat build-up would be destructive to the health of the batteries. The gentleman walked away with a look of disgust and I felt bad that I had come across so forcefully (happens too often).
    Well, the gist of all this is that this A.M. I went to the flying field and informed all in attendance that I was intending to perform and experiment in which I would charge a Lithium Poly pack in 12 minutes at a rate of 5C and we would see what would happen, I being ready to sacrifice the pack if that indeed took place. Well, in 12 minutes exactly, the charger shut down and indicated that charge completion had occurred. I immediately disconnected the pack and ran to the rest of the group in attendance and had everybody feel the temperature of the pack and to everyone's amazement the pack was not even luke warm. I subsequently flew the pack and thought that I got a little longer flight time than I normally do (probably all in my head). Now, these packs have never been balanced, and in fact have no balance plugs. 
    So, am I recommending that everyone start charging at 5C? Definitely not !  I'm certainly no battery guru, but I am of the opinion that there may be a lot more for us to learn about the current technology and I'm certain the developments in the near future will surprise many (including me).
    Georgie

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