Tapping Vcc before current sensor for BEC's

ArduCopter Copter 4.3
1

Today I made the decision to tap Vcc before the current sensor to power the BEC’s on a 650 class copter. The BEC’s will power the Cube (MAUCH BEC), a HereLink, a FPV camera, and a mapping camera. I suspect the total load will be less than an 1 AMP.

I made this decision for convivence of wiring.

This copter will user either a 8000mAh or 12000mAh battery.

Other than setting the “reserve” mAh on the battery failsafe to consider the load of the electronics, are there any other parameters or operational considerations I should consider with this configuration?

I can change the configuration if necessary - but if there is little or no down side, I’d prefer to keep it as it is.

I’m wondering - there might even be some benefits to this configuration - as the current sensor (Mauch) will only see the motors load.

I’d appreciate any advice or comments as appropriate. Thank you!

vcc tap
vcc tap1322×1458 285 KB

2

Usually we position the current sensor to measure all load including accessories. I can’t immediately think of a benefit to excluding the accessories.

Vcc usually means the regulated supply voltage, like 5.0vdc

Probably Vbat or B+ might OK to use for the unregulated battery voltage. Just so everyone is on the same page.

3

Thanks @xfacta -

Interesting - on the PDB’s I’ve used to date, the pads with battery voltage are labeled Vcc.

Yes - this arrangement isn’t ideal. The issue is the difficulty connecting a tap from the battery lines on such short runs. I did it on my 450-class copter, and it wasn’t much fun.

I’m just trying to be on the lookout for “gotchas.”

4

You can definitely do what you are proposing, you just have to be aware the consumed current/capacity measured by Ardupilot will be just slightly off

5

So the current sensor won’t include the BEC’s. If you leave the battery connected but don’t start motors, the current sensor indication would indicate almost 0, but after C/1A (as you suspect) the battery will be empty.

6

True. But I can’t think of any instance where I might do this.