I have done this power layout to ensure power failsafe if something goes wrong.

 

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Comment by Josh Potter on February 18, 2013 at 9:06am

Is it safe to feed in to different BEC's on the input side? (not the outputs)


Developer
Comment by Bill Bonney on February 18, 2013 at 9:07am
Are all the BECs outputting the same voltage? If you have any difference current will flow from the higher to the lower as the system will want to normalize the voltage to be constant. It can't so you will have a BEC or ESC start to overheat.

It much better for failsafe redundancy to switch on failure to a new supply circuit. Redundancy just by parrallisation only works if the component that fails, fails open-circuit.
Comment by Christiaan van Vollenstee on February 18, 2013 at 9:52am

The 2 becs on the 7.4's are the same the one on the 14.8 is probaly .2 different, but that sould not be a problam because se APM is setup to take power from somewhere else.

 

The reason why I done this layout is that when the motor fails I still have servos and apm and if anyone of the 7.4v fail I have another one powering the apm and the servos, I recon the reciver will power the APM if the other 7.4 fail.

Comment by Peter Meister on February 18, 2013 at 10:17am

Looks good to me Christiaan, I do similar but use a batshare device and double the batteries to my RX and I also separate power to input and output rails as you do. I believe this save's us from a lot of the issues we see with brown outs and such, not too mention the fault tolerance it provides. Because I use the batshare I do not have to worry on either side of the input of output that power will be lost, as well on the RX. So I have backups to both input and output and RX in less then a 1/2oz product. Check it out from Cermark, called the batshare.


Developer
Comment by Bill Bonney on February 18, 2013 at 10:17am
Can you explain which connector are connected where and how? Also if you JP1 in or out?

I'm assuming JP1 is in, and you have connected the RX with a three wire servo cable to PWM Inputs, the other two connections are on PWM outputs. If that's true, the RX will not power the servos from PWM outputs as there is a diode that stops current flow in that direction.
Comment by Christiaan van Vollenstee on February 18, 2013 at 10:34am

I found it.

here

 

 

Can you please show me screen shots of your setup?

Comment by Simon Wunderlin on February 18, 2013 at 11:29am

This is interesting, care to share a little bit more about your setup (wiring schematics an configuration).

Comment by Christiaan van Vollenstee on February 18, 2013 at 12:10pm

I am still in the designing phase and the I want the perfect power system. I used a one battery system to power everything and lost a plane that way because of a faulty solder.

Comment by Aleksandr on February 18, 2013 at 12:54pm

And what sense? If refuses APM that you can make of nothing. Reliability remains former

Comment by Gary McCray on February 18, 2013 at 1:07pm

Hi Christiaan,

If all BECs are linear and I presume 5 volts you might get away with this, I often paralleled linear BECs from identical ESCs without ill effect.

However, if any BEC is a switcher it will not work, switching BECs definitely do not like being paralleled.

They actively sample their outputs and if they see another power supply they compensate inappropriately.

However, if one BEC fails in your system it can either go to a short or an open. If it goes to an open your other BECs can take up the slack. If it goes to a short it will simply take out the other BECs too and worse since you are using the APM as the combiner it might take it out too.

Something like the above Bat Share device is a generally better solution because it will deal with either failure mode.

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