Hello folks,

I am relatively new to drones, especially the APM2.5 and am planning my first build.

The only real problem i have come up against is that i cant figure out how i am going to power the APM2.5 board!

I have read through all the pages i can find, and what it keeps coming back to is something like:

You can power it from the RC input, but also from the output with an ESC.

Now does this mean i can plug all my outputs from my 6ch RX into the inputs on the board, with the BEC from the ESC still going to my RX like normal?

Or does it mean i have to do the above - like normal - then plug some other power supply into one of the outputs on the APM2.5?

I understand the ESC must be in the outputs so the APM2.5 can control the throttle, but how can the board possibly get power from the input of the ESC?

Hope all that makes sense!

Any help would be much appreciated - as once i get this sorted out i can start assembling the parts!


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Which channel would you plug a standalone ESC with BEC into the APM2.5 inputs?

Also, it may be listed somewhere but what is the power consumption like on the APM2.5? Just trying to figure out what size battery i would need for the dedicated ESC with BEC...


You're going to use a stand-alone ESC (ie: an ESC not actually being used for anything?) into the APM input just to use it's BEC?  Why not just get a proper power supply?

Anyway, channel # doesn't matter. The power and ground lines are common right across.

The load, I've measured about 200mA IIRC, with all the options plugged in.  It's not much.  An 800mAh battery would last a long time. 

Thanks for the explanation. That makes sense.

I guess i will just run the RX into the input of APM2.5 like normal then.

If i only have this one source of power into the APM2.5 do i need to change the default JP1 - if so, is it a soldered jumper?


APM2.5 + 3DR radio + External GPS + Multiplex Rx on mine draws 200ma, with slight ripple.
I supply it with an el cheapo esc 3a bec (linear type) connected to the o/p side of the apm2.5 board,
Jumper in place. The Rx power is taken from the i/p side of the APM board(through the channel leads),
this is the only supply, Works fine for me, never ever had a supply problem!

However, the wiki states that the supply voltage to o/p side of apm2.5 should be 5v37 +- 0v5
If you supply it outside that tolerance is entirely your decision!
If you crash using low volts, its your fault!
If you crash using the correct supply voltage, its still your fault!

I prefer the linear becs, but a couple of suggestions:
If you use servos(Gimbal etc), then consider using a separate psu
If you use 4s then use a separate psu
Ideally use a separate psu anyway (this is for other reasons than the arguments here)

Ok, so is the JP1 jumper in place the default? And this means you have to have 2 sources of power like you have?


"I supply it with an el cheapo esc 3a bec (linear type) connected to the o/p side of the apm2.5 board,"

Which port do you plug it into on the output side? Any of them?

Also, what battery do you use for the standalone ESC?

Thanks so much

Jumper should be in place on a complete board, but probably be missing on a board supplied with headers to solder on!
Easy to check though! It's the only jumper on the board, and its placed immediately next to the output pins.

Bec supply to the output side can be on any output channel

"Ok, so is the JP1 jumper in place the default? And this means you have to have 2 sources of power like you have?"

Think you misunderstood! I only have one supply and that is to the output side of the apm2.5

12v power comes from the batteries that plug into the ESC's.

Generally ESC's, in addition to providing power output to the motors, also provide 5V regulated output through the cables that plug into the RX. That's the 3 wire cable coming out of the ESC. Red is your 5v+. Black is ground -. White is the signal.

The red 5V wire is used to power the RX and Servos. ESC's generally have a limit of about 3Amps they can provide to power the servo's and RX. So if you don't have many servo's you can use that 5v coming out of the ESC to power the APM.

Alternatively you can use a dedicated BEC that simply converts 12v to 5v.

How many amps do i need on my BEC if i have 4 micro servos and an APM2.5 with sensors? 2A, 3A, 5A?


Quick question, since I forgot my electricity classes:

Why are all of my four 3DR 20AMP esc's showing 10v output on my multimeter when its written their output should be 5v 2amp?

Well, since my USB cable is powering the input rail with the same multimeter reading, I guess I need to re-learn how to read the said multimeter...

Regarding JP1, if I just connect the output and input rails on +- row, thats the same effect than closing the jumper?

Thanks guys!

I think i have the APM2.5 power supply sorted out now:

- leave the JP1 jumper in place

- 800mAh 3S w/ 3A BEC connected to one of the APM2.5 outputs



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