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

Sat Oct 10 16:31:00 AKDT 2015

George,

The manufacturers (Turnigy, Giant Power, and GensAce/Tattu) I talked to said while the battery will tolerate those higher charge rates, they will reduce the life of the pack and that for best battery life to keep charge rate at 2c or less.

-           Robert Beaubien
-           Sr. Software Architect
-           Kool Software LLC

“Dear Algebra, Please stop asking us to find your X.  She's never coming back and don't ask Y.”

From: NSRCA-discussion [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of George Kennie via NSRCA-discussion
Sent: Saturday, October 10, 2015 5:09 PM
To: Jay Marshall <lightfoot at sc.rr.com>; General pattern discussion <nsrca-discussion at lists.nsrca.org>
Subject: Re: [NSRCA-discussion] LiPo Fun Fact 'O The Day

I'm no expert, but what about the ads you see touting that a particular pack can be
charged at a C-12 rate ?

I once inquired regarding charging at a rate higher than C- 1 on this forum and was
dramatically warned about the serious increase in heat that would be generated with
deleterious consequences (either fire or battery destruction ). Subsequent to this warning,
and being at the local flying field accompanied by a group of flying buddies I mentioned
that I thought that the warning might be an over-reaction. I therefore took a discharged
pack and charged it at a C- 5 rate. In exactly 12 minutes the bell went off indicating that
the pack had reached charged state. Immediately upon the charger indicator displaying the
fully charged symbol I disconnected the pack and ran with the battery to the group of
guys in attendance so that they could feel the temperature of the just charged pack and
to everyone's amazement there was no discernible difference in temp, in fact everyone
conceded that the pack actually felt COOL ! Now I realize that there was no electronic
sensor involved, only trying to sense an increase in the temp by the feel in your palm.

Does that mean that I charge my batteries at C-12 ? Uh-uh , but I have charged @ C-3,
but my charger keeps defaulting to C-1 so mostly that's what I use.

G.

On Sat, Oct 10, 2015 at 5:25 PM, Jay Marshall via NSRCA-discussion <nsrca-discussion at lists.nsrca.org<mailto:nsrca-discussion at lists.nsrca.org>> wrote:
Have you heard of a Peltier device?

Jay Marshall

From: NSRCA-discussion [mailto:nsrca-discussion-bounces at lists.nsrca.org<mailto:nsrca-discussion-bounces at lists.nsrca.org>] On Behalf Of Ron Hansen via NSRCA-discussion
Sent: Saturday, October 10, 2015 12:49 PM
To: 'James Hiller'; 'General pattern discussion'
Subject: Re: [NSRCA-discussion] LiPo Fun Fact 'O The Day

I would say anytime you pass current (electricity) through anything it will get warmer.  In the case of your toaster oven, the wiring leading to your toaster gets hotter when the toaster turns on and returns to ambient when it turns off.  Same for a battery, you are passing current through the battery so it must heat up and then returns to ambient once the charging process stops. When you run your Lipos in your plane, the batteries heat up because you again are passing current through them.  They heat up more during discharge because we discharge them much quicker than we charge them.  If you re-charge a lipo in 7 minutes I bet they get really hot.

Endothermic and exothermic all depends on where you draw the boundary.  Something always absorbs heat and something always releases heat.

From: NSRCA-discussion [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of James Hiller via NSRCA-discussion
Sent: Saturday, October 10, 2015 11:40 AM
To: 'General pattern discussion'
Subject: Re: [NSRCA-discussion] LiPo Fun Fact 'O The Day

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<mailto:ed_alt at hotmail.com>
CC: chuenkan at comcast.net<mailto:chuenkan at comcast.net>; nsrca-discussion at lists.nsrca.org<mailto:nsrca-discussion at lists.nsrca.org>
From: klhoard at outlook.com<mailto: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<mailto:-klhoard at outlook.com>

From: Ed Alt
Sent: Friday, October 9, 2015 21:09
To: Keith Hoard
Cc: chuenkan at comcast.net;General<mailto: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<mailto: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<mailto: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<mailto: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<mailto:klhoard at outlook.com>

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