82 MODEL AVIATION
IN THE MARCH 2004 issue I provided answers to some frequently
asked questions (FAQs) that resulted from the “From the Ground Up”
installments that I wrote. That article included seven reader questions
and their answers (Q-and-As) from the past few months. There are still
many questions to be answered; as such, I’ve been asked to author this
new monthly column expressly for addressing any and all
beginner/sport-flier inquiries.
Each Q-and-A will have a sequential reference number, so I’ll start
this column with the eighth question. Because publication space is
limited, it has been decided to run five to 10 Q-and-As per column; the
number will depend on the overall complexity of the answers.
In addition, I plan on answering questions to be posted on MA’s
section of the AMA Web site (http://modelaircraft.org/mag/index.htm),
where space is not a limiting factor. So make sure you read your
monthly MA and then refer to the Web site.
You might notice that I have finally included my E-mail address
with my writings. I’ve resisted doing this for years because I might
never be able to leave my basement shop/computer station. As does
any modeler, I like to get out and fly because that’s what it is all about.
Keeping that in mind, I hope you understand that I can’t answer
everyone personally.
At times I will communicate with you directly, especially if I don’t
understand your concerns or problems. But even though I can’t answer
or acknowledge everyone, I do promise to read every single word that
arrives in my mailbox.
As do most people these days, unfortunately I receive a
considerable amount of spam, or junk mail. To make sure I read every
one of your E-mail messages, in the “Subject” line please type
“AMA—FAQ” and then whatever subject you like. This will “flag” it
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
[email protected]
Leaving RC transmitters on for long periods of time with
antennas retracted or collapsed, as shown, is a bad idea.
Inexpensive Hobbico Digital Voltmeter Mk III places a load on the
battery and tells you when it is time to recharge.
Top: receiver-type Ni-Cd packs with four cells each. Bottom:
cells not yet made into pack. There is no such thing as a one-cell,
4.8 volt Ni-Cd pack!
May 2004 83
so that I make sure to read it.
Should you choose to write a letter instead of E-mailing, send it to
AMA Headquarters in Muncie IN and address it “ATTN: Bob Aberle,
FAQ Department.” The staff will forward letters to me on a prompt and
regular basis. With all that in mind, let’s get started!
Q8: “I noticed that you referred to four- and five-cell receiver battery
packs in your series, but I have a single-cell pack rated at 4.8 volts and
was wondering what voltage it can reach before needing a recharge.”
A8: Your battery pack may look like a single battery cell, but because
it is identified as having 4.8 volts, it contains four individual cells. If
you multiply the nominal cell voltage of a Ni-Cd or NiMH battery
cell—1.2 volts—by 4, you get the 4.8 volts. Most of these four-cell
receiver battery packs have simple heat-shrink-wrap cases. If you look
closer, you can probably see the outline of the four cylindrical battery
cells under the thin wrap.
Receiver battery packs usually comprise four Ni-Cd or NiMH cells.
Some of the Pattern and helicopter pilots like faster servo response time
and slightly higher output torque, and therefore go to a five-cell pack.
As for what voltage to go down to before you stop flying and
recharge, I recommend roughly 4.8 volts. A fully charged four-cell
pack can reach as high as 5.6 volts. The time it takes to get from 5.6 to
the 4.8-volt mark is a function of the battery’s rated capacity. The
higher the capacity (expressed in mAh), the longer it takes to get to that
recommended minimum voltage. An average 600 mAh-capacity, fourcell
battery pack should take approximately two hours to reach that
minimum.
Much of that has to do with the type of model flown. An RC
sailplane will take far fewer commands than an RC Aerobatics model.
Control commands use up battery power! When the time to reach 4.8
volts starts to get shorter and shorter, the capacity is diminishing and
replacement becomes inevitable.
You can easily check receiver-battery voltage at the field with a
meter such as the Hobbico Digital Voltmeter Mk III I described in the
“Battery Basics” article (on page 59 of the October 2003 MA). This
inexpensive instrument not only places a load on the battery, but it tells
you when it is time to recharge.
Q9: “When I get home from the flying field I usually leave my
transmitter and receiver on for approximately eight hours, until they
are almost completely discharged. Then the night before I fly I
recharge using the RC manufacturer’s charger for 15 hours. Is this a
good process?”
A9: I’m not in favor of your process at all! Leaving your transmitter
and receiver on for eight hours will probably take the batteries all the
way down, and they might even go into reversal. That fact alone could
easily ruin a battery pack.
I assume that when you leave your transmitter on for that long
period, you have the antenna retracted or collapsed. If so, the
Futaba transmitter’s voltage meter reads 10.9 at almost full
charge. It may quickly drop to 10.0 but stay there for next hour or
two before dropping to where alarm goes off (roughly 8.8 volts).
L-R: Hitec Neon’s throttle control lever is on rear of case. Futaba
Super 7’s throttle control lever is on front.
Shows location of throttle control lever on Hitec Neon. Move
lever left or right to obtain high or low throttle.
Futaba Super 7’s throttle control lever moves up and down. High
throttle is in uppermost position (shown); idle (low throttle) is at
bottom.
84 MODEL AVIATION
transmitter output circuit is detuned and the
output current may be exceeding normal
operating parameters. Therefore, you are
doing your transmitter no good in this regard.
On the receiver side, as the batteries wear
down, the servos will get jittery. Then later
the control may go hard over, resulting in a
stalled servo or more likely a damaged servo
gear. In both cases, the only way to discharge
a battery pack, be it transmitter or receiver, is
with a standard discharge or cycling device.
These units are set to cut off or stop
discharging when the voltage gets to
something near 1.0 volt per cell. By using
such a device, you will never take a Ni-Cd or
NiMH battery down too far! But even more
important, you shouldn’t be taking your
batteries down after each flight session. The
so-called “memory effect” has always been a
debatable subject.
The best recommendation is to cycle or
discharge-test your battery packs every
month or two. Your way is unnecessarily
losing you a great deal of battery life.
Q10: “I have a Futaba T6XA transmitter
with an eight-cell 600 mAh capacity Ni-Cd
battery pack. I tested the pack on a cycler
and determined that it had an actual capacity
of 585 mAh. When I get to the flying field the
meter reads 10.9 volts, and then in 15
minutes of operation it is down to 10.5 volts,
and in 15 more minutes it is down to 10.2
volts. Is this normal?”
A10: Since you tested the battery pack and
found that it was close to the rated capacity of
600 mAh, yes, it is normal! Most RC
transmitters consume roughly 200-250 mA
total current when in operation. With the
usual 600 mAh battery pack, you should
easily be able to obtain approximately two
hours of operation.
A typical Ni-Cd battery’s voltage tends to
drop off rather fast initially, and then it
reaches a point of 9.8-10.0 volts where it will
remain constant for quite awhile. I’ll bet that
you would obtain the two hours of operating
time before the voltage got down to 8.8 and
tripped the alarm built into your transmitter.
If the two hours weren’t enough, you
could purchase AA-size NiMH battery packs
of the same physical dimensions with
capacity ratings upward of 2000 mAh. That
would provide six hours and more of
operating time. But if you did that, you would
need a new charger that is capable of much
more current.
Q11: “I first bought the recommended Hitec
Neon three-channel RC system and then later
bought a basic four-channel system. I
realized right away that the throttle control
sticks were in different locations. As a
beginner, will this cause me any problems?”
A11: Not to be a wise guy, but I’ll start out
by answering that it shouldn’t, but it might!
As I explained early in the “From the Ground
Up” series, most of my RC transmitters have
two dual-axis control-stick assemblies with at
least four-channel control capability. But I
also own several three-channel systems,
including a Neon, that I use on some of my
RC sailplanes and parking-lot flyers as a
convenience. Three-channel systems aren’t
just for beginners.
The primary difference in the transmitter
configuration is the throttle control stick’s
location. Most three-channel transmitters,
such as the Neon, have the throttle control on
the rear of the case. This is so you can hold
the case with your left hand and finger the
throttle. Then your right hand is free to
operate the single dual-axis (steering and
elevation) control stick on the right side of
the front of the transmitter case.
On four-channel-function (and more)
systems there are two separate dual-axis
control-stick assemblies. You grip the
transmitter case with both hands, and all four
primary flight controls are located on the
front of it. Your left hand operates the throttle
channel control with a vertical (up-anddown)
motion.
So using the three-channel transmitter, the
throttle is a side-to-side motion; on a fourchannel,
dual-stick-assembly transmitter, the
throttle is an up-and-down motion. That stick
is set for high motor speed at the top and idle
at the bottom.
As I pointed out, my student had some
experience flying with a four-channel
transmitter. Then we went to the flying field
with the Neon three-channel system and used
a buddy-box trainer cable connecting it to
another transmitter.
My student immediately became slightly
confused with the new throttle-control
location; it actually bothered him for several
flights. That reaction prompted my comments
in the September issue.
The average sport flyer should be
proficient at flying with either throttle-control
location. The three-channel systems are
usually less expensive, so owning several can
be a real cost saver. I encourage you to own
both types of systems. When you are learning
to fly RC, it is best if you stick with one
transmitter configuration until you can
comfortably fly solo with no help from an
instructor pilot.
That concludes the published portion this
month. With each column I will try to include
a few photos to supplement the text where
possible.
It is obvious from this start that many
modelers have questions and concerns when
it comes to battery applications, charging
techniques, and general care, but there are
many other aspects to this hobby. I encourage
you to write or E-mail your questions about
anything with which you are having a
problem.
I am an electric-power enthusiast, but in
more than 50 years of modeling I have flown
glow, gas, diesel, rubber, CO2, and handlaunched
gliders. Try me with any and all of
your questions. If I can’t answer a question, I
network with a group of experts on a regular
basis to act as my consultants. Your questions
will get answered!
Also, please let me know if the answers
are too broad, too detailed, too long, or not
long enough! I need your input! MA
Edition: Model Aviation - 2004/05
Page Numbers: 82,83,84
Edition: Model Aviation - 2004/05
Page Numbers: 82,83,84
82 MODEL AVIATION
IN THE MARCH 2004 issue I provided answers to some frequently
asked questions (FAQs) that resulted from the “From the Ground Up”
installments that I wrote. That article included seven reader questions
and their answers (Q-and-As) from the past few months. There are still
many questions to be answered; as such, I’ve been asked to author this
new monthly column expressly for addressing any and all
beginner/sport-flier inquiries.
Each Q-and-A will have a sequential reference number, so I’ll start
this column with the eighth question. Because publication space is
limited, it has been decided to run five to 10 Q-and-As per column; the
number will depend on the overall complexity of the answers.
In addition, I plan on answering questions to be posted on MA’s
section of the AMA Web site (http://modelaircraft.org/mag/index.htm),
where space is not a limiting factor. So make sure you read your
monthly MA and then refer to the Web site.
You might notice that I have finally included my E-mail address
with my writings. I’ve resisted doing this for years because I might
never be able to leave my basement shop/computer station. As does
any modeler, I like to get out and fly because that’s what it is all about.
Keeping that in mind, I hope you understand that I can’t answer
everyone personally.
At times I will communicate with you directly, especially if I don’t
understand your concerns or problems. But even though I can’t answer
or acknowledge everyone, I do promise to read every single word that
arrives in my mailbox.
As do most people these days, unfortunately I receive a
considerable amount of spam, or junk mail. To make sure I read every
one of your E-mail messages, in the “Subject” line please type
“AMA—FAQ” and then whatever subject you like. This will “flag” it
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
[email protected]
Leaving RC transmitters on for long periods of time with
antennas retracted or collapsed, as shown, is a bad idea.
Inexpensive Hobbico Digital Voltmeter Mk III places a load on the
battery and tells you when it is time to recharge.
Top: receiver-type Ni-Cd packs with four cells each. Bottom:
cells not yet made into pack. There is no such thing as a one-cell,
4.8 volt Ni-Cd pack!
May 2004 83
so that I make sure to read it.
Should you choose to write a letter instead of E-mailing, send it to
AMA Headquarters in Muncie IN and address it “ATTN: Bob Aberle,
FAQ Department.” The staff will forward letters to me on a prompt and
regular basis. With all that in mind, let’s get started!
Q8: “I noticed that you referred to four- and five-cell receiver battery
packs in your series, but I have a single-cell pack rated at 4.8 volts and
was wondering what voltage it can reach before needing a recharge.”
A8: Your battery pack may look like a single battery cell, but because
it is identified as having 4.8 volts, it contains four individual cells. If
you multiply the nominal cell voltage of a Ni-Cd or NiMH battery
cell—1.2 volts—by 4, you get the 4.8 volts. Most of these four-cell
receiver battery packs have simple heat-shrink-wrap cases. If you look
closer, you can probably see the outline of the four cylindrical battery
cells under the thin wrap.
Receiver battery packs usually comprise four Ni-Cd or NiMH cells.
Some of the Pattern and helicopter pilots like faster servo response time
and slightly higher output torque, and therefore go to a five-cell pack.
As for what voltage to go down to before you stop flying and
recharge, I recommend roughly 4.8 volts. A fully charged four-cell
pack can reach as high as 5.6 volts. The time it takes to get from 5.6 to
the 4.8-volt mark is a function of the battery’s rated capacity. The
higher the capacity (expressed in mAh), the longer it takes to get to that
recommended minimum voltage. An average 600 mAh-capacity, fourcell
battery pack should take approximately two hours to reach that
minimum.
Much of that has to do with the type of model flown. An RC
sailplane will take far fewer commands than an RC Aerobatics model.
Control commands use up battery power! When the time to reach 4.8
volts starts to get shorter and shorter, the capacity is diminishing and
replacement becomes inevitable.
You can easily check receiver-battery voltage at the field with a
meter such as the Hobbico Digital Voltmeter Mk III I described in the
“Battery Basics” article (on page 59 of the October 2003 MA). This
inexpensive instrument not only places a load on the battery, but it tells
you when it is time to recharge.
Q9: “When I get home from the flying field I usually leave my
transmitter and receiver on for approximately eight hours, until they
are almost completely discharged. Then the night before I fly I
recharge using the RC manufacturer’s charger for 15 hours. Is this a
good process?”
A9: I’m not in favor of your process at all! Leaving your transmitter
and receiver on for eight hours will probably take the batteries all the
way down, and they might even go into reversal. That fact alone could
easily ruin a battery pack.
I assume that when you leave your transmitter on for that long
period, you have the antenna retracted or collapsed. If so, the
Futaba transmitter’s voltage meter reads 10.9 at almost full
charge. It may quickly drop to 10.0 but stay there for next hour or
two before dropping to where alarm goes off (roughly 8.8 volts).
L-R: Hitec Neon’s throttle control lever is on rear of case. Futaba
Super 7’s throttle control lever is on front.
Shows location of throttle control lever on Hitec Neon. Move
lever left or right to obtain high or low throttle.
Futaba Super 7’s throttle control lever moves up and down. High
throttle is in uppermost position (shown); idle (low throttle) is at
bottom.
84 MODEL AVIATION
transmitter output circuit is detuned and the
output current may be exceeding normal
operating parameters. Therefore, you are
doing your transmitter no good in this regard.
On the receiver side, as the batteries wear
down, the servos will get jittery. Then later
the control may go hard over, resulting in a
stalled servo or more likely a damaged servo
gear. In both cases, the only way to discharge
a battery pack, be it transmitter or receiver, is
with a standard discharge or cycling device.
These units are set to cut off or stop
discharging when the voltage gets to
something near 1.0 volt per cell. By using
such a device, you will never take a Ni-Cd or
NiMH battery down too far! But even more
important, you shouldn’t be taking your
batteries down after each flight session. The
so-called “memory effect” has always been a
debatable subject.
The best recommendation is to cycle or
discharge-test your battery packs every
month or two. Your way is unnecessarily
losing you a great deal of battery life.
Q10: “I have a Futaba T6XA transmitter
with an eight-cell 600 mAh capacity Ni-Cd
battery pack. I tested the pack on a cycler
and determined that it had an actual capacity
of 585 mAh. When I get to the flying field the
meter reads 10.9 volts, and then in 15
minutes of operation it is down to 10.5 volts,
and in 15 more minutes it is down to 10.2
volts. Is this normal?”
A10: Since you tested the battery pack and
found that it was close to the rated capacity of
600 mAh, yes, it is normal! Most RC
transmitters consume roughly 200-250 mA
total current when in operation. With the
usual 600 mAh battery pack, you should
easily be able to obtain approximately two
hours of operation.
A typical Ni-Cd battery’s voltage tends to
drop off rather fast initially, and then it
reaches a point of 9.8-10.0 volts where it will
remain constant for quite awhile. I’ll bet that
you would obtain the two hours of operating
time before the voltage got down to 8.8 and
tripped the alarm built into your transmitter.
If the two hours weren’t enough, you
could purchase AA-size NiMH battery packs
of the same physical dimensions with
capacity ratings upward of 2000 mAh. That
would provide six hours and more of
operating time. But if you did that, you would
need a new charger that is capable of much
more current.
Q11: “I first bought the recommended Hitec
Neon three-channel RC system and then later
bought a basic four-channel system. I
realized right away that the throttle control
sticks were in different locations. As a
beginner, will this cause me any problems?”
A11: Not to be a wise guy, but I’ll start out
by answering that it shouldn’t, but it might!
As I explained early in the “From the Ground
Up” series, most of my RC transmitters have
two dual-axis control-stick assemblies with at
least four-channel control capability. But I
also own several three-channel systems,
including a Neon, that I use on some of my
RC sailplanes and parking-lot flyers as a
convenience. Three-channel systems aren’t
just for beginners.
The primary difference in the transmitter
configuration is the throttle control stick’s
location. Most three-channel transmitters,
such as the Neon, have the throttle control on
the rear of the case. This is so you can hold
the case with your left hand and finger the
throttle. Then your right hand is free to
operate the single dual-axis (steering and
elevation) control stick on the right side of
the front of the transmitter case.
On four-channel-function (and more)
systems there are two separate dual-axis
control-stick assemblies. You grip the
transmitter case with both hands, and all four
primary flight controls are located on the
front of it. Your left hand operates the throttle
channel control with a vertical (up-anddown)
motion.
So using the three-channel transmitter, the
throttle is a side-to-side motion; on a fourchannel,
dual-stick-assembly transmitter, the
throttle is an up-and-down motion. That stick
is set for high motor speed at the top and idle
at the bottom.
As I pointed out, my student had some
experience flying with a four-channel
transmitter. Then we went to the flying field
with the Neon three-channel system and used
a buddy-box trainer cable connecting it to
another transmitter.
My student immediately became slightly
confused with the new throttle-control
location; it actually bothered him for several
flights. That reaction prompted my comments
in the September issue.
The average sport flyer should be
proficient at flying with either throttle-control
location. The three-channel systems are
usually less expensive, so owning several can
be a real cost saver. I encourage you to own
both types of systems. When you are learning
to fly RC, it is best if you stick with one
transmitter configuration until you can
comfortably fly solo with no help from an
instructor pilot.
That concludes the published portion this
month. With each column I will try to include
a few photos to supplement the text where
possible.
It is obvious from this start that many
modelers have questions and concerns when
it comes to battery applications, charging
techniques, and general care, but there are
many other aspects to this hobby. I encourage
you to write or E-mail your questions about
anything with which you are having a
problem.
I am an electric-power enthusiast, but in
more than 50 years of modeling I have flown
glow, gas, diesel, rubber, CO2, and handlaunched
gliders. Try me with any and all of
your questions. If I can’t answer a question, I
network with a group of experts on a regular
basis to act as my consultants. Your questions
will get answered!
Also, please let me know if the answers
are too broad, too detailed, too long, or not
long enough! I need your input! MA
Edition: Model Aviation - 2004/05
Page Numbers: 82,83,84
82 MODEL AVIATION
IN THE MARCH 2004 issue I provided answers to some frequently
asked questions (FAQs) that resulted from the “From the Ground Up”
installments that I wrote. That article included seven reader questions
and their answers (Q-and-As) from the past few months. There are still
many questions to be answered; as such, I’ve been asked to author this
new monthly column expressly for addressing any and all
beginner/sport-flier inquiries.
Each Q-and-A will have a sequential reference number, so I’ll start
this column with the eighth question. Because publication space is
limited, it has been decided to run five to 10 Q-and-As per column; the
number will depend on the overall complexity of the answers.
In addition, I plan on answering questions to be posted on MA’s
section of the AMA Web site (http://modelaircraft.org/mag/index.htm),
where space is not a limiting factor. So make sure you read your
monthly MA and then refer to the Web site.
You might notice that I have finally included my E-mail address
with my writings. I’ve resisted doing this for years because I might
never be able to leave my basement shop/computer station. As does
any modeler, I like to get out and fly because that’s what it is all about.
Keeping that in mind, I hope you understand that I can’t answer
everyone personally.
At times I will communicate with you directly, especially if I don’t
understand your concerns or problems. But even though I can’t answer
or acknowledge everyone, I do promise to read every single word that
arrives in my mailbox.
As do most people these days, unfortunately I receive a
considerable amount of spam, or junk mail. To make sure I read every
one of your E-mail messages, in the “Subject” line please type
“AMA—FAQ” and then whatever subject you like. This will “flag” it
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
[email protected]
Leaving RC transmitters on for long periods of time with
antennas retracted or collapsed, as shown, is a bad idea.
Inexpensive Hobbico Digital Voltmeter Mk III places a load on the
battery and tells you when it is time to recharge.
Top: receiver-type Ni-Cd packs with four cells each. Bottom:
cells not yet made into pack. There is no such thing as a one-cell,
4.8 volt Ni-Cd pack!
May 2004 83
so that I make sure to read it.
Should you choose to write a letter instead of E-mailing, send it to
AMA Headquarters in Muncie IN and address it “ATTN: Bob Aberle,
FAQ Department.” The staff will forward letters to me on a prompt and
regular basis. With all that in mind, let’s get started!
Q8: “I noticed that you referred to four- and five-cell receiver battery
packs in your series, but I have a single-cell pack rated at 4.8 volts and
was wondering what voltage it can reach before needing a recharge.”
A8: Your battery pack may look like a single battery cell, but because
it is identified as having 4.8 volts, it contains four individual cells. If
you multiply the nominal cell voltage of a Ni-Cd or NiMH battery
cell—1.2 volts—by 4, you get the 4.8 volts. Most of these four-cell
receiver battery packs have simple heat-shrink-wrap cases. If you look
closer, you can probably see the outline of the four cylindrical battery
cells under the thin wrap.
Receiver battery packs usually comprise four Ni-Cd or NiMH cells.
Some of the Pattern and helicopter pilots like faster servo response time
and slightly higher output torque, and therefore go to a five-cell pack.
As for what voltage to go down to before you stop flying and
recharge, I recommend roughly 4.8 volts. A fully charged four-cell
pack can reach as high as 5.6 volts. The time it takes to get from 5.6 to
the 4.8-volt mark is a function of the battery’s rated capacity. The
higher the capacity (expressed in mAh), the longer it takes to get to that
recommended minimum voltage. An average 600 mAh-capacity, fourcell
battery pack should take approximately two hours to reach that
minimum.
Much of that has to do with the type of model flown. An RC
sailplane will take far fewer commands than an RC Aerobatics model.
Control commands use up battery power! When the time to reach 4.8
volts starts to get shorter and shorter, the capacity is diminishing and
replacement becomes inevitable.
You can easily check receiver-battery voltage at the field with a
meter such as the Hobbico Digital Voltmeter Mk III I described in the
“Battery Basics” article (on page 59 of the October 2003 MA). This
inexpensive instrument not only places a load on the battery, but it tells
you when it is time to recharge.
Q9: “When I get home from the flying field I usually leave my
transmitter and receiver on for approximately eight hours, until they
are almost completely discharged. Then the night before I fly I
recharge using the RC manufacturer’s charger for 15 hours. Is this a
good process?”
A9: I’m not in favor of your process at all! Leaving your transmitter
and receiver on for eight hours will probably take the batteries all the
way down, and they might even go into reversal. That fact alone could
easily ruin a battery pack.
I assume that when you leave your transmitter on for that long
period, you have the antenna retracted or collapsed. If so, the
Futaba transmitter’s voltage meter reads 10.9 at almost full
charge. It may quickly drop to 10.0 but stay there for next hour or
two before dropping to where alarm goes off (roughly 8.8 volts).
L-R: Hitec Neon’s throttle control lever is on rear of case. Futaba
Super 7’s throttle control lever is on front.
Shows location of throttle control lever on Hitec Neon. Move
lever left or right to obtain high or low throttle.
Futaba Super 7’s throttle control lever moves up and down. High
throttle is in uppermost position (shown); idle (low throttle) is at
bottom.
84 MODEL AVIATION
transmitter output circuit is detuned and the
output current may be exceeding normal
operating parameters. Therefore, you are
doing your transmitter no good in this regard.
On the receiver side, as the batteries wear
down, the servos will get jittery. Then later
the control may go hard over, resulting in a
stalled servo or more likely a damaged servo
gear. In both cases, the only way to discharge
a battery pack, be it transmitter or receiver, is
with a standard discharge or cycling device.
These units are set to cut off or stop
discharging when the voltage gets to
something near 1.0 volt per cell. By using
such a device, you will never take a Ni-Cd or
NiMH battery down too far! But even more
important, you shouldn’t be taking your
batteries down after each flight session. The
so-called “memory effect” has always been a
debatable subject.
The best recommendation is to cycle or
discharge-test your battery packs every
month or two. Your way is unnecessarily
losing you a great deal of battery life.
Q10: “I have a Futaba T6XA transmitter
with an eight-cell 600 mAh capacity Ni-Cd
battery pack. I tested the pack on a cycler
and determined that it had an actual capacity
of 585 mAh. When I get to the flying field the
meter reads 10.9 volts, and then in 15
minutes of operation it is down to 10.5 volts,
and in 15 more minutes it is down to 10.2
volts. Is this normal?”
A10: Since you tested the battery pack and
found that it was close to the rated capacity of
600 mAh, yes, it is normal! Most RC
transmitters consume roughly 200-250 mA
total current when in operation. With the
usual 600 mAh battery pack, you should
easily be able to obtain approximately two
hours of operation.
A typical Ni-Cd battery’s voltage tends to
drop off rather fast initially, and then it
reaches a point of 9.8-10.0 volts where it will
remain constant for quite awhile. I’ll bet that
you would obtain the two hours of operating
time before the voltage got down to 8.8 and
tripped the alarm built into your transmitter.
If the two hours weren’t enough, you
could purchase AA-size NiMH battery packs
of the same physical dimensions with
capacity ratings upward of 2000 mAh. That
would provide six hours and more of
operating time. But if you did that, you would
need a new charger that is capable of much
more current.
Q11: “I first bought the recommended Hitec
Neon three-channel RC system and then later
bought a basic four-channel system. I
realized right away that the throttle control
sticks were in different locations. As a
beginner, will this cause me any problems?”
A11: Not to be a wise guy, but I’ll start out
by answering that it shouldn’t, but it might!
As I explained early in the “From the Ground
Up” series, most of my RC transmitters have
two dual-axis control-stick assemblies with at
least four-channel control capability. But I
also own several three-channel systems,
including a Neon, that I use on some of my
RC sailplanes and parking-lot flyers as a
convenience. Three-channel systems aren’t
just for beginners.
The primary difference in the transmitter
configuration is the throttle control stick’s
location. Most three-channel transmitters,
such as the Neon, have the throttle control on
the rear of the case. This is so you can hold
the case with your left hand and finger the
throttle. Then your right hand is free to
operate the single dual-axis (steering and
elevation) control stick on the right side of
the front of the transmitter case.
On four-channel-function (and more)
systems there are two separate dual-axis
control-stick assemblies. You grip the
transmitter case with both hands, and all four
primary flight controls are located on the
front of it. Your left hand operates the throttle
channel control with a vertical (up-anddown)
motion.
So using the three-channel transmitter, the
throttle is a side-to-side motion; on a fourchannel,
dual-stick-assembly transmitter, the
throttle is an up-and-down motion. That stick
is set for high motor speed at the top and idle
at the bottom.
As I pointed out, my student had some
experience flying with a four-channel
transmitter. Then we went to the flying field
with the Neon three-channel system and used
a buddy-box trainer cable connecting it to
another transmitter.
My student immediately became slightly
confused with the new throttle-control
location; it actually bothered him for several
flights. That reaction prompted my comments
in the September issue.
The average sport flyer should be
proficient at flying with either throttle-control
location. The three-channel systems are
usually less expensive, so owning several can
be a real cost saver. I encourage you to own
both types of systems. When you are learning
to fly RC, it is best if you stick with one
transmitter configuration until you can
comfortably fly solo with no help from an
instructor pilot.
That concludes the published portion this
month. With each column I will try to include
a few photos to supplement the text where
possible.
It is obvious from this start that many
modelers have questions and concerns when
it comes to battery applications, charging
techniques, and general care, but there are
many other aspects to this hobby. I encourage
you to write or E-mail your questions about
anything with which you are having a
problem.
I am an electric-power enthusiast, but in
more than 50 years of modeling I have flown
glow, gas, diesel, rubber, CO2, and handlaunched
gliders. Try me with any and all of
your questions. If I can’t answer a question, I
network with a group of experts on a regular
basis to act as my consultants. Your questions
will get answered!
Also, please let me know if the answers
are too broad, too detailed, too long, or not
long enough! I need your input! MA
