Receiver Power System Requirements; Recommended Power System Guidelines - Spektrum DX6i Manual

With all radio installations, it is vital 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), power bus (if used).
While Spektrum's receivers' 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 recommend that
a current and volt-meter (Hangar 9 HAN172) be used. Plug the volt-meter 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.
: The optional Flight Log has a built-in volt meter and it can be used to perform this test.
2. With the current meter in line 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.
: The Flight log can not measure current draw. Please note that if the flight log is used to
measure voltage, the HAN172 current meter still must be used to measure the draw of the servos.
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. 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.
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 incorporate 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.
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