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

Sat Oct 10 15:11:09 AKDT 2015

Take an Ambien and get some sleep, will ya?

-Keith Hoard
-klhoard at outlook.com

From: Ed Alt
Sent: Saturday, October 10, 2015 17:32
To: Keith Hoard;NSRCA List
Subject: RE: [NSRCA-discussion] LiPo Fun Fact 'O The Day

Too funny.   Enough silliness, there's  playoff baseball to watch.

To: nsrca-discussion at lists.nsrca.org
Date: Sat, 10 Oct 2015 15:36:41 -0400
Subject: Re: [NSRCA-discussion] LiPo Fun Fact 'O The Day
From: nsrca-discussion at lists.nsrca.org
Also, you’re charging at 2C, too high.

From: Keith Hoard [mailto:klhoard at outlook.com] 
Sent: Saturday, October 10, 2015 15:33
To: 'nsrca-discussion' <nsrca-discussion at lists.nsrca.org>
Subject: RE: [NSRCA-discussion] LiPo Fun Fact 'O The Day

Well, there’s your error.  You measured the temps in Fahrenheit, not Celsius.

From: Ed Alt [mailto:ed_alt at hotmail.com] 
Sent: Saturday, October 10, 2015 11:11
To: Keith Hoard <klhoard at outlook.com>; NSRCA List <nsrca-discussion at lists.nsrca.org>
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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