I-24
With all radio installations it is vital that the onboard power
system provides adequate power without interruption to the
receiver even when the system is fully loaded (servos at
maximum flight loads). This becomes especially critical with
giant-scale models that utilize multiple high torque/ high
current servos. Inadequate power systems that are unable to
provide the necessary minimum voltage to the receiver during
flight loads have become the number one cause of in-flight
failures. Some of the power system components that affect the
ability to properly deliver adequate power include: the selected
receiver battery pack (number of cells, capacity, cell type, state
of charge), switch harness, battery leads, regulator (if used) and
power bus (if used).
While JR’s receiver’s minimum operational voltage is 3.5
volts, it is highly recommended the system be tested per the
guidelines below to a minimum acceptable voltage of 4.8
volts during ground testing. This will provide head room to
compensate for battery discharging or if the actual flight loads
are greater than the ground test loads.
1. When setting up large or complex aircraft with multiple high
torque servos, it’s highly recommended that a current and
voltmeter (HAN172) be used. Plug the voltmeter in an open
channel port in the receiver and with the system on, load
the control surfaces (apply pressure with your hand) while
monitoring the voltage at the receiver. The voltage should
remain above 4.8 volts even when all servos are heavily
loaded.
Note
: The optional Flight Log has a built-in voltmeter and
it can be used to perform this test.
2. With the current meter inline with the receiver battery lead,
load the control surfaces (apply pressure with your hand)
while monitoring the current. The maximum continuous
recommended current for a single heavy-duty servo/battery
lead is three amps while short duration current spikes
of up to five amps are acceptable. Consequently, if your
system draws more than three amps continuous or five
amps for short durations, a single battery pack with a single
switch harness plugged into the receiver for power will
be inadequate. It will be necessary to use multiple packs
with multiple switches and multiple leads plugged into the
receiver.
3. If using a regulator, it’s important the above tests are done
for an extended period of 5 minutes. When current passes
through a regulator, heat is generated and this heat causes
the regulator to increase resistance, which in turn causes
even more heat to build up (thermal runaway). While a
regulator may provide adequate power for a short duration,
it’s important to test its ability over time as the regulator
may not be able to maintain voltage at significant power
levels over time.
4. For really large aircraft or complex models (for example
35% and larger or jets), multiple battery packs with
multiple switch harnesses are necessary or in many cases
one of the commercially available power boxes/ busses is
recommended. No matter what power systems you choose,
always carry out test #1 above making sure that the receiver
is constantly provided with 4.8 volts or more under all
conditions.
5. The latest generation of Nickel-Metal Hydride batteries
incorporates a new chemistry mandated to be more
environmentally friendly. These batteries when charged with
peak detection fast chargers have tendencies to false peak
(not fully charge) repeatedly. These include all brands of
NiMH batteries. If using NiMH packs, be especially cautious
when charging making absolutely sure that the battery is
fully charged. It is recommended to use a charger that can
display total charge capacity. Note the number of mAh put
into a discharged pack to verify it has been charged to full
capacity.
Receiver Power System Requirements
Recommended Power System Guidelines