Hello, I’m currently working on a self driving car project with two MITSUBA M2096D-Ⅲ Brushless DC Motor, a UNICELL 12.8V DC Car Battery and a Odrive 3.6.
Currently at 12 Volts, the wheels run incredibly slow and we wanted to step up the voltage going into the odrive3.6, however when we tried to use a step-up voltage regulator to 18 Volts, the step-up voltage regulator would fry.
The second issue was that the odrive would reach max DC overtrip bus voltage and shut down. I tried to enable the brake resistor but then the wheels would start spinning the wrong way and the overtrip bus voltage would trigger anyways.
We plan to buy a diode and a suitable brake resistor as the diode would stop the flow of regen current.
However I am unsure of which diode and brake resistor is able to handle this issue.
The voltage regulator can output max 5A.
Hi there,
Unfortunately, powering a motor driver from a DC/DC converter can be a bit difficult. Is there any possibility that you add more batteries in series, or wind the motor with a higher KV?
If you’ll use the DC/DC converter, you definitely need a much stronger one – 5A at 18V is only 90W, and your motor supports up to 5kW peak. I’d look for a converter that can output at least 1kW.
To choose a brake resistor, you can use some of the same math as used for the regen clamp: ODrive Regen Clamp Datasheet — ODrive Documentation 0.6.10 documentation
You’ll also need a diode rated for the same output current as your DC/DC regulator. It’ll also help to add some capacitance to the output of the diode to allow for some voltage smoothing, I’d add around 1mF (or more if possible). Note you’ll definitely need some sort of soft-start or precharge circuit to prevent inrush / sparking.
Overall, I would strongly recommend just moving to a higher voltage battery pack, or ordering the motor with a higher KV rating, that’ll be much easier than trying to use a DC/DC converter here.