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BasicESC and Reverse Current

(Denizhan Dalgic) #1

We are building our ROV and we had one worry.

Is it possible for BasicESC to cause reverse current from its input or does it have a protection against it?

To be clear, I am NOT talking about reverse thruster operation, but about the possibility of current coming FROM the ESC TO the input supply.

(Adam) #2


Yes, the the Basic ESC R3 does send small amounts of reverse current/a back EMF voltage spike back to the supply when reversing rotation or stopping a motor/thruster. This active braking is baked into the BlHeli_S firmware the Basic ESC runs, but the spike is a very small amount of energy and should not affect anything unless it is particularly sensitive.

This is of no concern at all for a battery, and most power supplies have no issue as well. If running the thrusters in air this spike in somewhat greater, and some more sensitive power supply models can react to the short instantaneous reverse current by tripping their internal protection and temporarily shutting off. In general though, we have never seen this happen in actual use underwater, water does most of the braking.

Unfortunately there is no way to completely disable this without significantly modifying and recompiling the firmware, we have spoken to the BlHeli developer about this and it would take a lot of work to change the behavior without causing other issues.


(Denizhan Dalgic) #3

Thank you for your quick response, @adam.

We are powering the vehicle through external power supplies (not using battery).

To be sure, we are planning on connecting diodes and for that we need to know the numbers. Is there any documentaiton of this or can you provide the information?

That’d be greatly appreciated as we, as a team, aim for the highest stability and durability, no matter the quality/capabilities of the power supply.

(Adam) #4

We do not have much information on this beyond my previous post. In the worst case of hammering a T200 thruster back and forth from full forward to full reverse in air with a 4S battery, the spikes are on the order of 30 V or so, with an overall duration of about 40-60 ms. However, the peaks of ~30 V are only reached for tiny fraction of that time. The back EMF is essentially undetectable in water, and has never tripped even the most sensitive power supplies in my experience.