[NSRCA-discussion] LiPo Fun Fact 'O The Day

[James Hiller]

Ed, what may be more important is, understanding the voltage increase due to
temperature increase of maybe 20 - 30 degrees after charging before use on a
hot summer afternoon and the potential over voltage state.
 
I've heard of some E-Pylon fliers warming their batteries to increase
voltage to hopefully get an advantage.
 
Please comment.
Thanks
Jim 
 
From: NSRCA-discussion [mailto:nsrca-discussion-bounces at lists.nsrca.org] On
Behalf Of Ed Alt via NSRCA-discussion
Sent: Saturday, October 10, 2015 8:11 AM
To: Keith Hoard; NSRCA List
Subject: Re: [NSRCA-discussion] LiPo Fun Fact 'O The Day
 
There are minor effects (the endothermic reaction) and there are major
effects (the internal resistance of the cells).  The packs get warmer when
charged.  I just tried it with a pair of Gens Ace 5S 5300 30C packs at a 10A
charge rate each.  The starting point was from a storage charge.  They've
been sitting in the basement shop for months.  Pack one measured 65.1F and
pack 2 was at 65.2F before starting the charge. Here are the readings from a
brief constant current charge that I stopped at 1250 mA put into each.
 
At 500 mA delivered, pack 1 was 67.9 F, pack 2 67.4 F
At 650 mA, 68.5 & 67.7
At 700 mA, 70 & 68.6
At 1000 mA, 71.9 & 69.9
At 1100 mA, 72 & 70.4
At 1250 mA, 72.5 & 70.9.
 
Maybe you could go down to some much lower charge rate at which the
endothermic reaction cooling dominates, but that's not realistic. 
 
Ed
  _____  

To: ed_alt at hotmail.com
CC: chuenkan at comcast.net; nsrca-discussion at lists.nsrca.org
From: klhoard at outlook.com
Subject: RE: [NSRCA-discussion] LiPo Fun Fact 'O The Day
Date: Fri, 9 Oct 2015 23:54:24 -0500
Not silly at all.  You didn't account for the chemical reaction of the
electrolyte during the charge process.
 
  The term the PhD's use to describe the reaction is "endothermic"(gets
colder) and has to do with that whole "energy cannot be created or
destroyed, just moved around" rule.
 
    There are several papers on the internet written by the molecular
scientists who designed LiPos.
 
-Keith Hoard
-klhoard at outlook.com
 
 

From: Ed Alt
Sent: Friday, October 9, 2015 21:09
To: Keith Hoard
Cc: chuenkan at comcast.net;General pattern discussion
Subject: Re: [NSRCA-discussion] LiPo Fun Fact 'O The Day
 
 
That wasn't a guess, it was a statement of fact.  This is getting silly.

On Oct 9, 2015, at 9:09 PM, Keith Hoard <klhoard at outlook.com> wrote:
Nope.  If you had another guess?

Sent from my iPad

On Oct 9, 2015, at 20:09, Ed Alt <ed_alt at hotmail.com> wrote:
They do warm up when charging, even at low rates.  It's the physics behind
Ohms law that governs some of that.  It may not be very noticeable, but it
is happening nonetheless.

On Oct 9, 2015, at 8:03 PM, Phil Spelt via NSRCA-discussion
<nsrca-discussion at lists.nsrca.org> wrote:
I would say "C" below:  I have never had a lipo pack get warm during
charging.  That's because i always charge somewhere between 1.8-2.0 C.  For
my electric planes I buy enough batteries so I do not have to hurry-charge
in order to get back into the air.  I charge the lipos in my starter & glow
igniter at home in the shop when I have plenty of time.  Now, in the
interest of full disclosure, I do not use $150.00 battery packs, and none of
my electric planes are for pattern.
 
Phil Spelt, KCRC Emeritus, Secretary
AMA 1294, Scientific Leader Member
SPA L-18, Board Member
(865) 435-1476v  (865) 604-0541c
 
 

During charging, a LiPo battery becomes:
 
A)     Warmer
B)     Colder
        C)   None of the above
        D)  All of the above
 
--Keith Hoard
--klhoard at outlook.com
 

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