FOR THOSE WHO are alarmed by that
nasty little spark you see when connecting a
battery pack to the ESC, there’s a solution.
You can find it in the article “How to
prevent sparking,” which is in the February
2009 Ampeer online newsletter. See the
“Sources” list for the Web address.
When connecting a battery pack to the
controller, strong sparking commonly
occurs. Fast-charging the controller filter
capacitors causes this. The higher the
voltage (the higher the cell count), the lower
the internal resistance (and the better the
quality of the pack), the better the capacitors
in the controller, and the higher the capacity
of the capacitors, the bigger the spark that
occurs.
Besides the small shock (because of the
spark), the capacitors’ charging current may
be, in extreme cases, so big that damage or
destruction of the capacitors occurs. A simple
procedure exists to
eliminate sparking
when connecting the
battery pack. This
inexpensive
modification
eliminates sparking,
and thus protects the
filter capacitors.
1. Connect the negative leg of the battery
to the negative wire on the controller.
2. In the positive circuit, connect the
positive leg of the controller to the auxiliary
connector (to which a resistor with 10s of
ohms is connected in serial). This will limit
the charging current when connecting the
wires and will charge the filter capacitors
without sparking.
3. Connect the power wires (sparking
will not occur).
4. Start the motor.
the auxiliary connector. The current is
small (1-2 amps) and lasts only for a short
time. Nor are there requirements on the
resistor; any type is sufficient, such as
metalized 0.6 watt, size 0207, and value of
20 to 50 ohms, depending on the battery
pack’s voltage.
On a four- to six-cell Li-Poly pack, use
20 ohms; for 10-cell Li-Poly, use 33 ohms;
for 12-cell and up, use 51 ohms. It is
unnecessary to use these exact values
because of wide variation.
Connect the new auxiliary connector.
Capacitors are charged with small current;
sparking will not occur. Connect the power
connectors (sparking will not occur).
Leave the auxiliary leads connected. The
main current to the controller and motor
during operation passes through these power
connectors and conductors. See the wiring
illustration for further clarification.
RCadvisor’s Model Airplane Design Made
Easy by Carlos Reyes uses straightforward
explanations to teach important design
tradeoffs and how to choose among them. In
this 208-page book, you will learn when it
makes sense to use one of the innovative
KFM airfoils; you’ll find out what that
means.
The latest research and techniques are
explained in clear language. Carlos explains
the special challenges faced by the smaller
models and how to overcome them
Carlos sets easy rules for selecting the
right power system, both gas and electric,
and provides the pros and cons of canard
and multiwing configurations. Figure out
how to choose the right material for each
part of the airplane and learn a step-bystep
design process that includes goal
setting and flight-testing.
Also included are in-depth discussions of
important topics such as airfoils and wing
design, including the sources of air drag and
how to minimize their impact.
2.4 GHz on a Budget: There have been
many low-cost 2.4 GHz systems on the
market lately—particularly as part of RTF
models. I was curious and found one offered
by Air Land & Sea Hobby for $67.95
including S&H. The system included a
transmitter, receivers, software, and USB
cable. The company sent one for my review.
The TurBORIX is a full-range, 2.4 GHz,
six-channel radio, and it can be set up for
airplanes or helicopters. Programming is
done through the PC and included software.
This software may not be compatible with
some forms of Windows, such as Vista; it is
compatible with all forms of Windows XP.
The system is set up for primary batteries
(eight AA) but can easily be converted to
take rechargeable packs. It comes with a
charge jack that is compatible with Futaba
wall warts.
Although there is no meter to let you
know the battery’s state of charge, an LED
that changes from
green to yellow to
red as the pack
discharges gives
you some
indication. The
radio draws
approximately 180
mA, so a 600 mAh
pack should
comfortably provide
two hours of flying
with a good safety
margin.
My resources for evaluating a radio are
limited, but Dan Thompson (see the
“Sources” list if you want to e-mail him
with questions) collaborated with me and
learned some interesting things about the
system. It uses dual receivers that are
similar to the DSM2 systems.
There was some question about the
bind/range check button. Dan verified with
a Dunehaven spectrum analyzer that there
is no reduction in power with the button
depressed. Range-check can be done by
removing the antenna, which is good, since
it gives you a check that the small wire
inside the antenna has not broken.
The manual that comes with the system
is useless, and the distributor is working
with the manufacturer to fix the problem.
Meanwhile, anyone who needs a manual
can drop me a note.
You must set up the TurBORIX with the
software provided for your computer, and it
has all of the normal functions one would
expect from a computer radio. The only
problem is that unless you take your laptop
to the field, you can’t make adjustments or
change from one model to another.
Check out the screen shot. It shows you
a typical screen for programming the
transmitter. Programs can be saved, so you
can essentially cover an unlimited number
of models.
I have been flying the system for more
than a month, three days a week, and, in a
couple of cases, at a rich 2.4 GHz
environment. It has been as solid as a rock.
Although I wouldn’t want to chance one of
these budget radios in a $5,000 Scale or 3-
D model, it seems more than adequate for
the sport flier who is on a budget.
Are you confused by digital spread
spectrum? The “Sources” list contains a
Web site address that has an excellent
explanation of all the systems.
The quest for the ultimate charger
continues. Following the success of its
Triton series of chargers, ElectriFly ups
the ante with two new AC (alternating
current/DC (direct
current), “do-itall”
units.
The Triton EQ
claims to be an
upgrade for the
popular Triton Jr.
but is much more
than that. With up
to 5 amps of
charging power,
you have the
balancing
capability for both
Li-Poly and
LiFePO4 (A123)
technology that
has as many as six
cells in a pack.
ElectriFly has
also given the user
the option of
disabling the timer
function so that it can be used for forming
new Ni-Cd/NiMH packs. Space is too
limited to cover all the capabilities here,
but you can review the specs and download
the manual (see the Sources list for the
Web address).
Giving you even more charge power
(up to 8 amps), the Triton2 EQ adds 10-
battery-favorites memory and the same tiltup
reverse LED screen, making it much
easier to read, even in direct sunlight.
Programming is identical to that of the
earlier Triton2 charger. All details and a
downloadable manual are available.
Both chargers come with two adapter
boards that cover almost all the existing
battery balancing plugs on the market. I
did have to make one for my packs that
employs a Cellpro balancing plug.
New player in the Li-Poly Arena: Evan
Chapkis has released his new line of
PowerEdge Li-Poly packs, ranging from
800 mAh to 5000 mAh. My first test on all
packs is to fully charge them and then
subject them to the trusty CBA II analyzer
from West Mountain Radio.
I was pleasantly surprised to find that
my sample of the PowerEdge came out at
exactly the rated capacity. Most Li-Poly
packs fall a bit short of that, even at the
standard discharge rate (C/5) to check
capacity.
Lacking the equipment to take the
packs much higher than 140 watts, flying
them is next. I found them to perform well,
so I offered the sample to a couple of my
flying buddies to try. Both ordered two
each of the same 3S-2200 packs from
PowerEdgeRC.com.
I am not about to waste the
PowerEdge packs on the bench running
hundreds of cycles, to see how they fare
under artificial cycling.
Reader Questions:
“I have a World Models EP Mustang and
put the brushless-geared replacement motor
in it along with the 25amp ESC that goes
with that motor.
“Does it need a higher amperage ESC to
handle the 2200 mAh, 11.1-volt Li-Poly pack?
Also what cheaper replacement motor (like a
Tower Pro) would be better than the 400-class
geared brushless motor I have now?”
If the larger battery is the same voltage
as the one it replaces, there may be (at most)
a small increase in current because of the
larger battery maintaining its voltage better
than the old battery.
The main determinants of the current
seen by the ESC are the motor, gearbox, and
propeller. Changing any of these will change
the current. A larger propeller (in either
diameter or pitch) will draw more current
than a smaller propeller.
When making these kinds of changes to a
power system, check the performance with a
wattmeter. It will tell you at a glance how
much current is being drawn. Then you will
know for sure if any of your components are
seeing more current than they can handle.
Why guess when you can know for sure?
Modify a PC Power Supply (Update):
Thanks to Andrew Batts for the Web site
address, which you can find in the “Sources”
list. Some tips for increasing the output
current may be useful.
Use Only Brand X-Approved Parts: I’m
seeing Li-Poly packs with the admonishment
not to charge with any other brand of charger,
because circuit protection won’t allow them to
charge properly or something along those lines.
Until a vendor sends me a pack with a
“unique” circuit installed, I think you can
take this recommendation in the same fashion
we read, “Use only Brand X-approved parts.”
It’s marketing hype at its best.
The Battery Clinic Web site has moved. See
the “Sources” list for the new address. MA
Sources:
The Battery Clinic
12219 NW 9th Ln.
Newberry FL 32669
www.hangtimes.com/redsbatteryclinic.html
Ampeer online, February 2009:
http://homepage.mac.com:80/kmyersefo/am
pfeb09/ampfeb09.htm
RCadvisor’s Model Airplane Design Made
Easy
www.rcadvisor.com/book
Air, Land & Sea Hobby
(877) 230-2085
www.airlandseahobby.com
Dan Thompson
[email protected]
RC model reviews:
www.rcmodelreviews.com/spreadspectrum0
1.shtml
ElectriFly
(217) 398-8970
www.electrifly.com
Power Edge RC
(813) 765-0124
www.poweredgerc.com
Desktop Power Supply from a PC
http://web2.murraystate.edu/andy.batts/ps/P
OWERSUPPLY.HTM