[NSRCA-discussion] NiMH follow up

[John Pavlick]

Ed,
"C" stands for "Capacity". Therefore a C/10 charge rate for a 2200 mAh pack
is indeed 220 mA (1 10th the capacity). Sounds simple so far, now for the
confusing part. If you take these numbers literally, you would think that at
C/10 you should charge for 10 hours and at C/1 you should charge for 1 hour.
C/2 means charge for 2 hours. Not really. In reality a C/10 charge rate
usually takes 16 hours to fully charge a discharged battery. Maybe that's
where the confusion comes in. Luckily you really only need to use a few
different charge rates: C/10 for 16 hours is a slow / overnight charge. 2C
or 4C is good for fast charging NiMH's and NiCds respectevly. NiMH's don't
like to be charged quite as fast as NiCds so I usually charge them at 2C for
a little over half an hour after they're conditioned at the C/10 rate. A
good NiCd pack will accept 4C for about 15 minutes although smaller
batteries (<500mAh) aren't really too happy with this. To condition ne
batteries, I charge at C/10, then discharge at 500mA (not critical but you
should do it at a rate that is safe for the battery). I repeat this process
at least 3 times on a new pack. I use an Alpha 4 so it gives me the battery
capacity after discharging. You will see the capacity go up as you cycle a
new pack. A good one should reach 90% capacity (or more) after a few
cycles - if it does, it's ready to use. Hope this answers your question.
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 Ed Deaver
Sent: Monday, February 27, 2006 12:57 AM
To: NSRCA Mailing List
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


    _______________________________________________
    NSRCA-discussion mailing list
    NSRCA-discussion at lists.nsrca.org
    http://lists.nsrca.org/mailman/listinfo/nsrca-discussion




--
No virus found in this outgoing message.
Checked by AVG Free Edition.
Version: 7.1.375 / Virus Database: 268.1.0/269 - Release Date: 2/24/06
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20060226/6ece501a/attachment.html