Radio Control Airplane - Dual Battery Power

Thread Starter

Garry48

Joined Jul 18, 2017
12
Radio Control Airplane using a 20 cc gas engine with solid state ignition. Hall effect sensor used to trigger the ignition. Ignition has a shielded spark plug.
I will be using 5 servos rated for 8.4 volts. Typically, they run with a 50 Hz signal, but different servos can have up to 400 Hz signal. Servos usually draw less than 2A unless they are stalled (5 servos at 2A = 10A, worst case).
The radio receiver operates on 2.4GHz. Supposedly, 2.4G is less prone to interference. However, recently a large airplane with a gas engine flew away and has not been found. :( It was not mine! :)

I want to be able to use two 8.4 volt (3A) LiPo batteries to power the receiver. I know there can be interference generated by the spark ignition system and servo motors. I have the circuit in MicroCap 12 (attached).

I plan on using two Schottky diodes to prevent a battery from back feeding a failed (low voltage) battery.
The switches are only used in testing to simulate the failure of a battery (LED fails to illuminate).

What do I need to add/change reduce the chance of interference being injected in to the circuit?
Are C3, C4, and C5 required?
Are D1 and D2 required?
Suggested improvements?

I'm planning on producing a PCB.

I don't understand the transient analysis. I probed the "OUT Voltage" and it shows 8.4 volts but the graph appears as a declining voltage, but each point is 8.4 volts. i would thing it should be a straight line (DC).

Comments?
circuit7.png
 

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LowQCab

Joined Nov 6, 2012
2,171
Batteries generally don't "fail", outright, for no apparent reason.
As long as the Batteries have only been used in parallel, for their entire history,
there won't be a problem with simply connecting them in parallel,
and disconnecting them from each other when not in use.

DO NOT use 2 Batteries which have different usage histories.

Buy an identical, matched "pair" of Batteries,
and always use them as a "pair",
and You won't have any Load-sharing problems.

The Diodes are just going to waste Power.
They will also cause the Flight-Controller to report Low-Battery-Voltage
before it's actually Low, ( which might be a good thing for Battery-Cycle-Life ).
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