84 MODEL AVIATION
THIS IS THE 10th monthly column in which you write in or Email
your questions, and I try to give you the best possible answers.
Each question is given a sequential number for identification
purposes. Because publication space is limited, part of each month’s
installment will appear here, and the columns in their entirety are
posted on the AMA Web site at www.modelaircraft.org/mag/
faq/index.asp.
Let’s start!
Q80: “I know years ago that you could purchase books containing
coordinates for plotting most known wing airfoils. I’ve heard that
information like this is now available on Web sites. If that is true
could you steer me to a particular Web site to get me started?”
A80: The airfoil program that comes to mind can be found at
www.profili2.com/eng/default.htm. At one time the Profili airfoil
program was available as “freeware.” From what I understand, it is
now offered on a trial basis for free, but after a limited time you
have to register and pay a fee.
I just called up the Web site and found that many new features
have been added. The claim is that the program now includes more
than 2,200 airfoils. It ties in easily with automated-drawing-type
programs.
If you are interested in model-aircraft design, you might want to
look into this program. I suspect there are others available, but this
is the one I know about.
Q81: “I took your advice and bought an AstroFlight 109 Lithium
Charger (the one with the green label). I certainly am pleased with
the overall operation. But one thing bothers me. When I attach the
two alligator clips to my automobile battery, the sparks go flying!
“I don’t like having sparks fly in close proximity to battery gas
vapors or even gasoline fumes. I’m sure if a main power switch
was incorporated into this charger, I wouldn’t have any problems.
Do you have any suggestions?”
A81: The reader is correct, and you may also have noticed the
“sparks fly” when connecting this charger (and many others) to carbattery
terminals. I haven’t had any problems with the sparks and
haven’t heard any complaints registered, but
I recently tried a solution on my own.
I could have drilled a hole in the charger
case and permanently installed a heavy-duty
toggle switch, but that would likely void the
terms of the charger’s warranty. I found a
better way.
I bought a heavy-duty, automotive-type
toggle switch from RadioShack (part
number 275-701, rated at 16 amps/12
VDC). All I did was cut the red (positive)
input wire (one of the long wires) close to
the alligator clip. The two wire ends went to
the two switch terminals. I had to add some
heat-shrink tubing to prevent a short circuit.
A nylon tie can act as a strain relief.
Since the switch wasn’t marked, I added
an “on” label. When not connected to the
car battery, this switch is “off.” After
connecting the alligator clips to the battery,
turn the switch on and operate the charger in
the normal manner. Doing it this way, there
will be no sparks!
When you’re finished with the charger, turn the switch off and
then remove the alligator clips from the battery terminal. Again, no
sparks!
I’ve seen switches that are intended for “in-line” insertion and
would probably be perfect for this application. If any reader can find
one of these, please drop me a note so I can share it with everyone.
Bob Aberle
F r e q u e n t l y A s k e d Q u e s t i o n s
E-mail: [email protected]
The Profili 2 Web site enables you to select, draw, and print 2,200
airfoil shapes. Shown is the site’s front page.
The AstroFlight Lithium Charger (part 109)
is shown before the external power on/off
switch has been added.
Bob chose this RadioShack automotive
switch to add to positive (red) wire on 12-
volt input side of Lithium Charger.
86 MODEL AVIATION
Bob cut red input wire then inserted switch into wire. Nylon tie FMA Direct’s VRLI voltage regulator weighs .12 ounce.
relieves some stress placed on switch terminals.
This is typically the way you charge an
RC transmitter battery pack with the
supplied dual-output charger.
Q82: “I just purchased an FMA
Direct/Kokam Li-Poly battery pack. It only
has two wires coming out of the pack. Do I
assume one is for charging and the other is
for operating my electric motor
(discharging)?”
A82: When I first read this E-mail, I
thought someone was pulling my leg. I
mentioned this note to several fellow club
members when I got to the flying field later
that same day. Surprisingly, I didn’t get a
“funny” reaction.
One member indicated that he owns a
new Hobbico ElectriFly Li-Poly battery
pack and that it has two sets of wires (a total
of four) exiting the pack; one pair goes to
your ESC and motor, and the other pair of
leads is for charging only. That charging
cable is routed through a special protection
or safety device that is built inside the
battery pack.
After hearing this, I contacted the reader
who had sent the original E-mail. He
explained that the first Li-Poly battery pack
he purchased was the ElectriFly and that it
indeed had two pairs of wires exiting the
pack.
Then he purchased that FMA Direct/
Kokam pack (www.fmadirect.com), and it
only had one pair of wires (a red and a
black) exiting the case. Since he was
already using separate cables to charge and
operate his motor, this new pack had
confused him. Then I understood and was
no longer laughing.
Hobbico has evidently addressed the
safety aspects of charging Li-Poly batteries
with this new “built-in” device. You can
obtain the same feature by adding an
FMA/Kokam Safety Guard external to the
pack. The mystery of the four-wire battery
pack is solved.
Q83: “With all the advantages being
pointed out concerning Li-Poly batteries for
electric-powered flight, I wondered if these
same batteries might be put to good use
powering RC systems used to control
fueled-engine aircraft? Is there some way I
might use several Li-Poly batteries to power
my RC receiver and servos? Would there be
any advantage in doing that?”
A83: Yes! Most RC airborne systems
(receiver and servos) are powered by fourcell
(4.8 volts nominal) Ni-Cd or NiMH
batteries. In some cases, five-cell packs
(6.0 volts nominal) are used to provide
faster servo transit time.
Each Li-Poly battery cell has a nominal
voltage of 3.7. A single Li-Poly cell would
not supply enough voltage to an RC
airborne system, but two Li-Poly cells in
series (7.4 volts nominal) would be far too
much voltage.
Several companies are marketing
voltage-reducing or -regulating devices that
drop the two-cell Li-Poly pack’s 7.4 volts
to 5.0 volts, specifically to operate an RC
airborne pack. I received a sample of FMA
Direct’s VRLI voltage regulator.
It is physically small—11⁄4 inches long,
3⁄4-inch wide, and 5⁄8-inch thick—and
weighs only .12 ounce. You insert this
device between the cable coming from your
receiver and a two-cell Li-Poly battery
pack.
As a bonus, the FMA engineers added
three colored LEDs to the VRLI circuit
board. When you turn on your RC receiver,
if the green LED glows, you have a
charged battery and are ready to fly. If the
yellow LED is on, your battery could use
recharging. If the red LED is on, don’t fly
until you recharge.
You have to work your numbers to
determine when using two Li-Poly batteries
is an advantage over using four Ni-Cd or
NiMH cells. You must consider the
batteries’ weights and their rated capacities.
This is just an introduction to the subject
matter.
Q84: “I’m afraid that constant charging of
my Ni-Cd and NiMH RC-system batteries
is going to prematurely wear them out and
force an early replacement. To help this
situation, I usually bring my RC
transmitters out to the field three or four
times before I resort to recharging them.
“Do you think to be on the safe side I
should resort to field fast charging those
batteries for a short time, to make sure I
have enough power to fly at a particular
field session?”
Below a typical FMA Direct/Kokam twocell
Li-Poly battery pack is the VRLI. It
regulates the voltage down to 5.0.
A84: This is the proverbial accident waiting
to happen! Regularly and frequently charging
your RC-system batteries using the supplied
dual-output-system chargers really doesn’t
take away from their normal life cycle. These
system chargers employ roughly a C/10, or
what we call an overnight rate.
A 500 mAh-rated Ni-Cd or NiMH
battery pack requires 500 divided by 10, or
50 mA, charge current. The overnight
period is understood as being at least 10
hours. But even 16 or 24 hours wouldn’t
have any negative effects on your batteries.
You can recharge them two, three, or four
times a week at the overnight rate, and they
still might last you five years or more.
However, if you fast-charge Ni-Cd and
NiMH cells—especially those not intended
for fast charging—you will reduce their
service life. In many cases, the battery
markings alone won’t really tell you if it
can accept fast or elevated charge currents.
Then on top of all this, your RC
transmitters were not set up for anything
but overnight battery charging. The internal
charging circuits (wiring and fuses) are
established for relatively low current levels.
If you put a field fast charger on your
transmitter, you stand a good chance of
burning out the internal charger wiring, or
at least the fuse.
Please take my word. Charge with your
RC-system charger every time before you
go flying. Make sure you leave the charger
on overnight. Do it as often as you have the
urge to fly. Going to the field several times
with an uncharged transmitter battery is a
bad idea! MA
Edition: Model Aviation - 2005/01
Page Numbers: 84,86,88
Edition: Model Aviation - 2005/01
Page Numbers: 84,86,88
84 MODEL AVIATION
THIS IS THE 10th monthly column in which you write in or Email
your questions, and I try to give you the best possible answers.
Each question is given a sequential number for identification
purposes. Because publication space is limited, part of each month’s
installment will appear here, and the columns in their entirety are
posted on the AMA Web site at www.modelaircraft.org/mag/
faq/index.asp.
Let’s start!
Q80: “I know years ago that you could purchase books containing
coordinates for plotting most known wing airfoils. I’ve heard that
information like this is now available on Web sites. If that is true
could you steer me to a particular Web site to get me started?”
A80: The airfoil program that comes to mind can be found at
www.profili2.com/eng/default.htm. At one time the Profili airfoil
program was available as “freeware.” From what I understand, it is
now offered on a trial basis for free, but after a limited time you
have to register and pay a fee.
I just called up the Web site and found that many new features
have been added. The claim is that the program now includes more
than 2,200 airfoils. It ties in easily with automated-drawing-type
programs.
If you are interested in model-aircraft design, you might want to
look into this program. I suspect there are others available, but this
is the one I know about.
Q81: “I took your advice and bought an AstroFlight 109 Lithium
Charger (the one with the green label). I certainly am pleased with
the overall operation. But one thing bothers me. When I attach the
two alligator clips to my automobile battery, the sparks go flying!
“I don’t like having sparks fly in close proximity to battery gas
vapors or even gasoline fumes. I’m sure if a main power switch
was incorporated into this charger, I wouldn’t have any problems.
Do you have any suggestions?”
A81: The reader is correct, and you may also have noticed the
“sparks fly” when connecting this charger (and many others) to carbattery
terminals. I haven’t had any problems with the sparks and
haven’t heard any complaints registered, but
I recently tried a solution on my own.
I could have drilled a hole in the charger
case and permanently installed a heavy-duty
toggle switch, but that would likely void the
terms of the charger’s warranty. I found a
better way.
I bought a heavy-duty, automotive-type
toggle switch from RadioShack (part
number 275-701, rated at 16 amps/12
VDC). All I did was cut the red (positive)
input wire (one of the long wires) close to
the alligator clip. The two wire ends went to
the two switch terminals. I had to add some
heat-shrink tubing to prevent a short circuit.
A nylon tie can act as a strain relief.
Since the switch wasn’t marked, I added
an “on” label. When not connected to the
car battery, this switch is “off.” After
connecting the alligator clips to the battery,
turn the switch on and operate the charger in
the normal manner. Doing it this way, there
will be no sparks!
When you’re finished with the charger, turn the switch off and
then remove the alligator clips from the battery terminal. Again, no
sparks!
I’ve seen switches that are intended for “in-line” insertion and
would probably be perfect for this application. If any reader can find
one of these, please drop me a note so I can share it with everyone.
Bob Aberle
F r e q u e n t l y A s k e d Q u e s t i o n s
E-mail: [email protected]
The Profili 2 Web site enables you to select, draw, and print 2,200
airfoil shapes. Shown is the site’s front page.
The AstroFlight Lithium Charger (part 109)
is shown before the external power on/off
switch has been added.
Bob chose this RadioShack automotive
switch to add to positive (red) wire on 12-
volt input side of Lithium Charger.
86 MODEL AVIATION
Bob cut red input wire then inserted switch into wire. Nylon tie FMA Direct’s VRLI voltage regulator weighs .12 ounce.
relieves some stress placed on switch terminals.
This is typically the way you charge an
RC transmitter battery pack with the
supplied dual-output charger.
Q82: “I just purchased an FMA
Direct/Kokam Li-Poly battery pack. It only
has two wires coming out of the pack. Do I
assume one is for charging and the other is
for operating my electric motor
(discharging)?”
A82: When I first read this E-mail, I
thought someone was pulling my leg. I
mentioned this note to several fellow club
members when I got to the flying field later
that same day. Surprisingly, I didn’t get a
“funny” reaction.
One member indicated that he owns a
new Hobbico ElectriFly Li-Poly battery
pack and that it has two sets of wires (a total
of four) exiting the pack; one pair goes to
your ESC and motor, and the other pair of
leads is for charging only. That charging
cable is routed through a special protection
or safety device that is built inside the
battery pack.
After hearing this, I contacted the reader
who had sent the original E-mail. He
explained that the first Li-Poly battery pack
he purchased was the ElectriFly and that it
indeed had two pairs of wires exiting the
pack.
Then he purchased that FMA Direct/
Kokam pack (www.fmadirect.com), and it
only had one pair of wires (a red and a
black) exiting the case. Since he was
already using separate cables to charge and
operate his motor, this new pack had
confused him. Then I understood and was
no longer laughing.
Hobbico has evidently addressed the
safety aspects of charging Li-Poly batteries
with this new “built-in” device. You can
obtain the same feature by adding an
FMA/Kokam Safety Guard external to the
pack. The mystery of the four-wire battery
pack is solved.
Q83: “With all the advantages being
pointed out concerning Li-Poly batteries for
electric-powered flight, I wondered if these
same batteries might be put to good use
powering RC systems used to control
fueled-engine aircraft? Is there some way I
might use several Li-Poly batteries to power
my RC receiver and servos? Would there be
any advantage in doing that?”
A83: Yes! Most RC airborne systems
(receiver and servos) are powered by fourcell
(4.8 volts nominal) Ni-Cd or NiMH
batteries. In some cases, five-cell packs
(6.0 volts nominal) are used to provide
faster servo transit time.
Each Li-Poly battery cell has a nominal
voltage of 3.7. A single Li-Poly cell would
not supply enough voltage to an RC
airborne system, but two Li-Poly cells in
series (7.4 volts nominal) would be far too
much voltage.
Several companies are marketing
voltage-reducing or -regulating devices that
drop the two-cell Li-Poly pack’s 7.4 volts
to 5.0 volts, specifically to operate an RC
airborne pack. I received a sample of FMA
Direct’s VRLI voltage regulator.
It is physically small—11⁄4 inches long,
3⁄4-inch wide, and 5⁄8-inch thick—and
weighs only .12 ounce. You insert this
device between the cable coming from your
receiver and a two-cell Li-Poly battery
pack.
As a bonus, the FMA engineers added
three colored LEDs to the VRLI circuit
board. When you turn on your RC receiver,
if the green LED glows, you have a
charged battery and are ready to fly. If the
yellow LED is on, your battery could use
recharging. If the red LED is on, don’t fly
until you recharge.
You have to work your numbers to
determine when using two Li-Poly batteries
is an advantage over using four Ni-Cd or
NiMH cells. You must consider the
batteries’ weights and their rated capacities.
This is just an introduction to the subject
matter.
Q84: “I’m afraid that constant charging of
my Ni-Cd and NiMH RC-system batteries
is going to prematurely wear them out and
force an early replacement. To help this
situation, I usually bring my RC
transmitters out to the field three or four
times before I resort to recharging them.
“Do you think to be on the safe side I
should resort to field fast charging those
batteries for a short time, to make sure I
have enough power to fly at a particular
field session?”
Below a typical FMA Direct/Kokam twocell
Li-Poly battery pack is the VRLI. It
regulates the voltage down to 5.0.
A84: This is the proverbial accident waiting
to happen! Regularly and frequently charging
your RC-system batteries using the supplied
dual-output-system chargers really doesn’t
take away from their normal life cycle. These
system chargers employ roughly a C/10, or
what we call an overnight rate.
A 500 mAh-rated Ni-Cd or NiMH
battery pack requires 500 divided by 10, or
50 mA, charge current. The overnight
period is understood as being at least 10
hours. But even 16 or 24 hours wouldn’t
have any negative effects on your batteries.
You can recharge them two, three, or four
times a week at the overnight rate, and they
still might last you five years or more.
However, if you fast-charge Ni-Cd and
NiMH cells—especially those not intended
for fast charging—you will reduce their
service life. In many cases, the battery
markings alone won’t really tell you if it
can accept fast or elevated charge currents.
Then on top of all this, your RC
transmitters were not set up for anything
but overnight battery charging. The internal
charging circuits (wiring and fuses) are
established for relatively low current levels.
If you put a field fast charger on your
transmitter, you stand a good chance of
burning out the internal charger wiring, or
at least the fuse.
Please take my word. Charge with your
RC-system charger every time before you
go flying. Make sure you leave the charger
on overnight. Do it as often as you have the
urge to fly. Going to the field several times
with an uncharged transmitter battery is a
bad idea! MA
Edition: Model Aviation - 2005/01
Page Numbers: 84,86,88
84 MODEL AVIATION
THIS IS THE 10th monthly column in which you write in or Email
your questions, and I try to give you the best possible answers.
Each question is given a sequential number for identification
purposes. Because publication space is limited, part of each month’s
installment will appear here, and the columns in their entirety are
posted on the AMA Web site at www.modelaircraft.org/mag/
faq/index.asp.
Let’s start!
Q80: “I know years ago that you could purchase books containing
coordinates for plotting most known wing airfoils. I’ve heard that
information like this is now available on Web sites. If that is true
could you steer me to a particular Web site to get me started?”
A80: The airfoil program that comes to mind can be found at
www.profili2.com/eng/default.htm. At one time the Profili airfoil
program was available as “freeware.” From what I understand, it is
now offered on a trial basis for free, but after a limited time you
have to register and pay a fee.
I just called up the Web site and found that many new features
have been added. The claim is that the program now includes more
than 2,200 airfoils. It ties in easily with automated-drawing-type
programs.
If you are interested in model-aircraft design, you might want to
look into this program. I suspect there are others available, but this
is the one I know about.
Q81: “I took your advice and bought an AstroFlight 109 Lithium
Charger (the one with the green label). I certainly am pleased with
the overall operation. But one thing bothers me. When I attach the
two alligator clips to my automobile battery, the sparks go flying!
“I don’t like having sparks fly in close proximity to battery gas
vapors or even gasoline fumes. I’m sure if a main power switch
was incorporated into this charger, I wouldn’t have any problems.
Do you have any suggestions?”
A81: The reader is correct, and you may also have noticed the
“sparks fly” when connecting this charger (and many others) to carbattery
terminals. I haven’t had any problems with the sparks and
haven’t heard any complaints registered, but
I recently tried a solution on my own.
I could have drilled a hole in the charger
case and permanently installed a heavy-duty
toggle switch, but that would likely void the
terms of the charger’s warranty. I found a
better way.
I bought a heavy-duty, automotive-type
toggle switch from RadioShack (part
number 275-701, rated at 16 amps/12
VDC). All I did was cut the red (positive)
input wire (one of the long wires) close to
the alligator clip. The two wire ends went to
the two switch terminals. I had to add some
heat-shrink tubing to prevent a short circuit.
A nylon tie can act as a strain relief.
Since the switch wasn’t marked, I added
an “on” label. When not connected to the
car battery, this switch is “off.” After
connecting the alligator clips to the battery,
turn the switch on and operate the charger in
the normal manner. Doing it this way, there
will be no sparks!
When you’re finished with the charger, turn the switch off and
then remove the alligator clips from the battery terminal. Again, no
sparks!
I’ve seen switches that are intended for “in-line” insertion and
would probably be perfect for this application. If any reader can find
one of these, please drop me a note so I can share it with everyone.
Bob Aberle
F r e q u e n t l y A s k e d Q u e s t i o n s
E-mail: [email protected]
The Profili 2 Web site enables you to select, draw, and print 2,200
airfoil shapes. Shown is the site’s front page.
The AstroFlight Lithium Charger (part 109)
is shown before the external power on/off
switch has been added.
Bob chose this RadioShack automotive
switch to add to positive (red) wire on 12-
volt input side of Lithium Charger.
86 MODEL AVIATION
Bob cut red input wire then inserted switch into wire. Nylon tie FMA Direct’s VRLI voltage regulator weighs .12 ounce.
relieves some stress placed on switch terminals.
This is typically the way you charge an
RC transmitter battery pack with the
supplied dual-output charger.
Q82: “I just purchased an FMA
Direct/Kokam Li-Poly battery pack. It only
has two wires coming out of the pack. Do I
assume one is for charging and the other is
for operating my electric motor
(discharging)?”
A82: When I first read this E-mail, I
thought someone was pulling my leg. I
mentioned this note to several fellow club
members when I got to the flying field later
that same day. Surprisingly, I didn’t get a
“funny” reaction.
One member indicated that he owns a
new Hobbico ElectriFly Li-Poly battery
pack and that it has two sets of wires (a total
of four) exiting the pack; one pair goes to
your ESC and motor, and the other pair of
leads is for charging only. That charging
cable is routed through a special protection
or safety device that is built inside the
battery pack.
After hearing this, I contacted the reader
who had sent the original E-mail. He
explained that the first Li-Poly battery pack
he purchased was the ElectriFly and that it
indeed had two pairs of wires exiting the
pack.
Then he purchased that FMA Direct/
Kokam pack (www.fmadirect.com), and it
only had one pair of wires (a red and a
black) exiting the case. Since he was
already using separate cables to charge and
operate his motor, this new pack had
confused him. Then I understood and was
no longer laughing.
Hobbico has evidently addressed the
safety aspects of charging Li-Poly batteries
with this new “built-in” device. You can
obtain the same feature by adding an
FMA/Kokam Safety Guard external to the
pack. The mystery of the four-wire battery
pack is solved.
Q83: “With all the advantages being
pointed out concerning Li-Poly batteries for
electric-powered flight, I wondered if these
same batteries might be put to good use
powering RC systems used to control
fueled-engine aircraft? Is there some way I
might use several Li-Poly batteries to power
my RC receiver and servos? Would there be
any advantage in doing that?”
A83: Yes! Most RC airborne systems
(receiver and servos) are powered by fourcell
(4.8 volts nominal) Ni-Cd or NiMH
batteries. In some cases, five-cell packs
(6.0 volts nominal) are used to provide
faster servo transit time.
Each Li-Poly battery cell has a nominal
voltage of 3.7. A single Li-Poly cell would
not supply enough voltage to an RC
airborne system, but two Li-Poly cells in
series (7.4 volts nominal) would be far too
much voltage.
Several companies are marketing
voltage-reducing or -regulating devices that
drop the two-cell Li-Poly pack’s 7.4 volts
to 5.0 volts, specifically to operate an RC
airborne pack. I received a sample of FMA
Direct’s VRLI voltage regulator.
It is physically small—11⁄4 inches long,
3⁄4-inch wide, and 5⁄8-inch thick—and
weighs only .12 ounce. You insert this
device between the cable coming from your
receiver and a two-cell Li-Poly battery
pack.
As a bonus, the FMA engineers added
three colored LEDs to the VRLI circuit
board. When you turn on your RC receiver,
if the green LED glows, you have a
charged battery and are ready to fly. If the
yellow LED is on, your battery could use
recharging. If the red LED is on, don’t fly
until you recharge.
You have to work your numbers to
determine when using two Li-Poly batteries
is an advantage over using four Ni-Cd or
NiMH cells. You must consider the
batteries’ weights and their rated capacities.
This is just an introduction to the subject
matter.
Q84: “I’m afraid that constant charging of
my Ni-Cd and NiMH RC-system batteries
is going to prematurely wear them out and
force an early replacement. To help this
situation, I usually bring my RC
transmitters out to the field three or four
times before I resort to recharging them.
“Do you think to be on the safe side I
should resort to field fast charging those
batteries for a short time, to make sure I
have enough power to fly at a particular
field session?”
Below a typical FMA Direct/Kokam twocell
Li-Poly battery pack is the VRLI. It
regulates the voltage down to 5.0.
A84: This is the proverbial accident waiting
to happen! Regularly and frequently charging
your RC-system batteries using the supplied
dual-output-system chargers really doesn’t
take away from their normal life cycle. These
system chargers employ roughly a C/10, or
what we call an overnight rate.
A 500 mAh-rated Ni-Cd or NiMH
battery pack requires 500 divided by 10, or
50 mA, charge current. The overnight
period is understood as being at least 10
hours. But even 16 or 24 hours wouldn’t
have any negative effects on your batteries.
You can recharge them two, three, or four
times a week at the overnight rate, and they
still might last you five years or more.
However, if you fast-charge Ni-Cd and
NiMH cells—especially those not intended
for fast charging—you will reduce their
service life. In many cases, the battery
markings alone won’t really tell you if it
can accept fast or elevated charge currents.
Then on top of all this, your RC
transmitters were not set up for anything
but overnight battery charging. The internal
charging circuits (wiring and fuses) are
established for relatively low current levels.
If you put a field fast charger on your
transmitter, you stand a good chance of
burning out the internal charger wiring, or
at least the fuse.
Please take my word. Charge with your
RC-system charger every time before you
go flying. Make sure you leave the charger
on overnight. Do it as often as you have the
urge to fly. Going to the field several times
with an uncharged transmitter battery is a
bad idea! MA