The Battery Clinic - 2012/03

www.ModelAviation.com March 2012 Model Aviation 103
electrics
Greg Gimlick
[email protected]
Readers’ battery questions answered
the battery clinic
Red Scholefield
[email protected]
“My fi rst experience programming the
ESC with the stick of my transmitter
was a nightmare! I also noticed that the
small, unmanageable aircraft are still
a prominent part of the offerings and
these are mostly, if not completely, of
the electric variety.
“If I were going to give a newcomer
advice on where to begin, I would say
go glow or gas and here is why: that will
force the person to fl y at a site where
The new AMA Youth Membership
program got me thinking: why
not sign up my great-grandson?
His father, U.S. Air Force Capt. Nick
Powers, built and fl ew a Gentle Lady
in the summer of 1993, while staying
with us as his father (my son) changed
stations. While Capt. Powers fl ies
C-130s, maybe the aviation bug will
hit Beck.
Of course, there are the usual
distractions that take our potential
modelers away from modeling. That is a
problem we have failed to successfully
address.
Reader Questions
J. Linghorne wrote:
“DeWalt has now started to sell
power tools that use Lithium-Ion cells.
The cells that are in the batteries look
like the 1100 mA A123 cells. I phoned
DeWalt and tried to get a spec sheet and
fi nd out more about the cells. I hoped
that they might be of use to me as a
modeler. I got nowhere; perhaps you can
answer my questions.
“1. Are the cells subject to thermal
runaway?
“2. What will happen if the cells are
accidently completely discharged? Will
they be ruined? Will they catch fi re or go
into thermal runaway, etc.?
“3. What will happen if they are
accidently overcharged? Will they
be ruined? Will they go into thermal
runaway, etc.?
“I thought that if they were going to
start to phase out the A123 cells that
I should buy some more and so [I]
purchased a new 36-volt pack. To my
horror, [I] discovered that it did not
contain 2300 A123 cells, but 20 1100
A123 cells. In other words, a 2200 mAh
pack made up of paralleled 1100 cells.
I would suggest that you should tell
modelers of this change.”
Answer: I have not seen or heard of
any instances of A123 cells going into
thermal runaway with chargers designed
to handle them. I suppose any battery
can be forced into thermal runaway if
subjected to enough current and voltage.
I have inadvertently discharged
several A123 packs and found that they
recover nicely on the next charge. They
are quite tolerant—much more so than
LiPo packs—of overcharge. If you use a
charger designed for A123 technology,
overcharge should not occur.
A bit of advice: never stock up on
battery packs because they begin to
deteriorate as soon as they
are manufactured. It’s
better to buy fresh packs as
needed, and the price seems
to decrease with time.
Mike Wilson wrote:
“Hi, Red. I always enjoy
reading about the latest
in battery technology,
as well as the history
behind where we are. I
did fi nd one item in your
November article that I
don’t completely agree
with. The line, ‘When I
watch the frustration of newcomers to
the hobby who have been led down the
gas- or glow-engine road,’ seemed like a
slap in the face to that side of the hobby.
“I began fl ying Control Line in the
early ’60s and glow was all we had. The
diffi culty, and what I believe [to be] the
main problem for the newcomer, both
then and now, is the size of the aircraft
they are encouraged to purchase.
“Back in those days, Cox was selling
small and very unmanageable aircraft to
newcomers and they just got frustrated
[and left] the hobby. Today, companies sell
larger and better-fl ying electric models but
they are built so light that they will hardly
stand even a slight impact, which is going
to happen. The electric systems are just as
complex and diffi cult to fi gure out as any
glow or gas confi guration.
The author recruited his 5-month-old greatgrandson,
Beck, as an AMA member under the
Youth Membership program.
PLUS:
> New AMA member
> C ratings comments
> New LiPo battery supplier
How can we manage the distractions that
cause young modelers to lose interest?104 Model Aviation March 2012 www.ModelAviation.com
competent fl iers are available to help the
novice, and where strict rules of safety
are observed. Taking an electric model
out to the local park where there is no
help available is a formula for disaster.
Not only will the novice be frustrated
beyond measure, the general public will
be at serious risk.
“Please don’t get me wrong, I enjoy
the electric side of the hobby and many
of my friends fl y them. I just believe that
either electric or glow/gas is a good way
to get into the hobby as long as there is
competent instruction. Both have pros
and cons, but the balance is fairly even.
“Just an old-timer with a different view.”
My reply: Mike makes a good point.
Start your fl ying with a club at which
you can get proper instruction and help
from experienced modelers. It will make
your start in the hobby much easier.
Dick Williams, Flowery Branch, Georgia,
wrote:
“Your ‘Battery Clinic’ article in the
September 2011 Model Aviation did
not mention soldering leads onto LiPo
batteries. Is that what you do and is this
a safe operation?”
Answer: No! Never try to solder leads
directly to LiPos, but you can on A123
cells if they have tabs. For LiPos, use the
leads (power and balancing) that come
on the pack.
C Ratings Comments
Dr. J.S. Miller, Professor of Biology, Goshen
College, Goshen, Indiana, wrote:
“I read with interest your comments
about battery C ratings in the July issue
of MA.
“I can give an additional, slightly
different, reason for preferring higher C
batteries. I’m fl ying a 3-pound Extreme
Flight electric Vanquish. It fl ies on a
2200 mA four-cell (14.4 volt) LiPo.
There’s a big difference between a
20C and a 30C battery. Because of its
lower resistance, the 30C battery has
approximately 50% more useful power
and 40-50% longer fl ight times.
“The 20C will give unlimited vertical
for about 1/3 of a fl ight; the 30C for
perhaps 3/4 of a fl ight.
the battery clinic
HAIYIN initial
discharges show
the packs meet
specifi cations.
HAIYIN high-rate discharges show capability in electric fl ight applications.
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K“The 30C battery gives longer
fl ights. With a 20C battery, I can only
use 1200-1300 mA of the battery’s
capacity. Beyond that, use of full
throttle (as in a touch-and-go) will drag
the voltage down below 13.7 volts. The
30C battery will supply 1800-1900 mA
of power before it gets pulled below
13.7 volts on full throttle.
“I have a Castle Ice Light ESC. As
someone mentioned in your article,
it’s really nice to be able to get out
all of that information after a fl ight.
That’s how I know how much mAh
of capacity was used from a battery at
any point in time during a fl ight. It also
reports on a continuous basis mAh of
power being drawn at any point in time,
LiPo battery voltage at any point in
time, ESC temperature, etc.
“I also have a Spektrum eight-channel
transmitter that has the downlink. One
of the things I monitor is LiPo voltage,
and an alarm goes off whenever the
battery voltage falls to 13.7 volts (3.425
volts per cell). The receiver is set to shut
off motor power when the voltage falls
to 3.3 volts per cell. I like the downlink
because it allows me to use more of the
battery’s charge without risking a lowvoltage
motor shutdown.
“I don’t like to have the motor cut out
during a fl ight. Depending on what I was
doing at the moment, it could certainly
crash an airplane. With the quiet electric
engine, one often doesn’t realize that the
motor has shut down; the electric motor
is too quiet, especially if there are other
airplanes in the air.”
Hitec Aurora 9
It has been reported that there may
be an issue with the algorithm used to
determine the remaining capacity shown
on the Aurora 9 transmitter display.
It can indicate much less than true
capacity, causing some to needlessly buy
replacement packs.
Always check your pack capacity
with any of the many available battery
maintenance devices.
New Battery Packs
Herewin has launched its HAIYIN
brand of RC LiPo battery packs. I
received two 3S 2200 30C packs to
review for my column.
The packs are assembled from cells
manufactured in a factory in southern
China. The high-quality packs are
competitively priced and perform well.
I tested the HAIYIN battery with
my Telemaster Electro. After 12 cycles
of an AXI 2826-12 turning a 13 x 6.5
APC e-propeller, the maximum current
drawn was 30 amps.
After a full-throttle run, nominal 350
watts, the capacity was charted (see
Figures 3A and 3B).
The pack was only slightly warm after
this run. A plot of the performance
at the cruise throttle setting—
approximately 20 amps—is shown in
Figures 3C and 3D.
I ran initial discharge capacity
tests (Figure 4A) at rates up to 4C
(the maximum my CBA III will
handle). After 12 cycles, I discharged
to see the individual cell capacity
(Figure 4B) and how well the cells
remained balanced.HAIYIN RC LiPo packs
Voltage: 7.4 volts to 22.2 volts (2S-6S)
Capacity: 500 mAh to 6000 mAh
Discharge “C” rate: 20C to 40C
Pack types: Regular, hard case,
transmitter, Flightmax, special sizes
For more information about
HAIYIN’s RC packs, see the company
website listed in “Sources.”
Avoid Confusion
There are battery packs/cells (Figure
5) that carry the “123A” designation.
These have been around for some
time and are popular camera batteries,
but are now being offered in Lithium
technology for high-powered flashlights.
These are not the A123 LiFe PO4
batteries we use for powering our
models. The 123A SureFire batteries
are 3-volt primary cells and nonrechargeable.
Eye Candy
Ed King built a beautiful rendition of
the venerable Lockheed Constellation,
“Connie.” I somehow lost the
information on this model. Hopefully,
Ed will see this and share the specifics
with us.
Spring Cometh
It’s time to give those battery packs a
good cycle check for capacity before you
launch into the 2012 flying season.
Wrapping Up
This wraps it up for another month.
Keep sending those cards and letters. No
email connection? Drop me a note at:
The Battery Clinic, 12219 NW 9th Ln., Newberry FL 32669