[NSRCA-discussion] charging

[Jay Marshall]

An interesting experiment. I'm almost tempted to try it using the temp probe
control on my Accu Cycle - using a low cost pack of course. Just increase
the charge rate until it cuts off. Dean is right, however, and these
"experiments" should be in a controlled and fail safe environment.
 
-----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 7:27 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] charging
 
<<<<So you were charging at 5C with a standard 2-wire to the battery
charger? Please be careful, my friend.>>>>
 
Yup, Deano.    Like I said, I'm not advocating that everybody do this. My
principle reason for doing the experiment was to determine if there was a
threshold for generating excessive heat within the pack, which did not
manifest itself. The charging was done in an area 50 feet from everything to
insure safety.
G. 
----- Original Message ----- 
From: Dean Pappas <mailto:d.pappas at kodeos.com>  
To: NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org>  
Sent: Friday, August 18, 2006 2:59 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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