Power module for more than 90 Amp draw

[Mugesh]

Hi people,
Im in the process of building my first hexacopter DJI F550 with pixhawk flight controller. I am using 15 A ESC's. So my hexacopter will draw 6*15 = 90 Amps all time. And someties it can go more than that.

The 3Dr power module can withstand only upto 90 A max. So it is not a good decision to use the power module for the hex as it might get burned up.

What should I do now for powering my pixhawk? Is there power modules available for more than 90 Amps?

 

[Mactadpole]

You don't want to continuously run your esc's at full capacity and beyond. It would be best to use eCalc for your configuration to get an idea of your actual amp draw or try to find someone who has posted their numbers for a similar configuration. I am not familiar with the F550 so can't help beyond that. If you do need something to allow you to monitor volt and amps via Pixhawk then you should build your own based on this link to the wiki: http://copter.ardupilot.com/wiki/common-using-a-pixhawk-with-6s-batteries/
I know it says 6s but it works for lower voltages too. I use it with 4s.

DO NOT use one of the ones off ebay unless you know from others that it works. I had all the parts to make my own but got lazy when I saw one ebay for like $12 and ordered it. Well, it desoldered itself on the test flight and my copter dropped about 10 meters to the ground and broke an arm and totaled my gimbal. I build my own and have never had an issue since. Lesson learned the hard way.

 

[Mugesh]

Thanks a lot mate! My amp draw might hang somewhere around 100 amps max according to my calculation. I will try to build my own circuit to power the hex with pihawk. Also trying to find someone who is using similar configuration! Thanks once again!

 

[Mactadpole]

From my experience you do not want to trust 15a esc's x6 with 100a. I actually have had several hexas that could peak at 90-100a on a full throttle climb and that was using 30a esc's. They were always warm after semi-aggressive flying. Can't imagine using 15a esc's.

 

[Mugesh]

So you recommend 30 A opto esc for the hex?? Is it going to be a big problem as my objective is to integrate hex with beaglebone black and create Linux based autopilot.
I can't afford any silly mistake

 

[Mactadpole]

Can you tell us the motors, props, batteries you plan to use? frame weight? Did you try eCalc with your setup? I thought you were using Pixhawk with arducopter? Now its beaglebone black?

 

[Mugesh]

I am using dji 920kv motor, 8*4.5 props, 5500 mAh 35 c 4S lipo. My agenda is to make it fly with Pixhawk and mission planner and get to know it better and then integrate it with beaglebone to create autonomous system as this is for an academic project.
And I am an amateur in Rc flying. I know it's going to be one hell of a task. But I am willing to learn and give my best.
Thank u for helping me big time!

 

[Mugesh]

The frame weight is 478 g and according to my rough estimate it is going to be around 2000 g with the battery included. My motor has 1200 g thrust each.

 

[mlebret]

So you will draw less than 5 Amp per motor (1/3 of max power) while hovering. Unless you want to fly at warp speed, you do not need 4S and 8x4.5 props but 3S and 11x4.5 props with your kv920 motors.

Marc

 

[Mugesh]

So your advice would be to use normal 3dr power module with max 90 A draw ?? My hex will not go beyond 90 A at any point right ??

 

[mlebret]

Unless you anchor it to the the ground and apply full power...

If you stay below 3 kg max take off weight, you are within the limits of your power module for normal GPS NAV flying.

Marc

 

[Mactadpole]

Thanks mlebret for helping! I input those rough numbers to eCalc too and I would definitely agree on the 3s battery and 11" props. The 15a esc's should be fine too. All of this stands as long as your in that 2000g UAW ranges.