Battery buffered power supply


I’m about to swap the steppers on my bench mill (beefed up Sieg SX3) for ODrives and KEDA 63-64 motors. I can’t quite get a grasp on what kind of power I’d need, but I suspect that my pair of 36V 10A (X+A and Y+Z) chinesium power supplies from eBay won’t cut it on their own. Combining them with three 12V starter batteries in series seems like a good option, but how? Would I need a diode to protect the PSU from overvoltage when braking? Would I need something like a current limiting resistor to prevent overloading the PSUs when charging?

I also have some 100V 15000 uF caps left over from a retired stereo project. Is that a viable alternative to batteries?

All axes are driven by ball screws with belt reduction, giving an effective 2mm travel per motor revolution. Max speed will be about 1000 rpm under load and hopefully 4-5000 rpm during rapids. Linear rails all round means minimal friction loss and possibly quite considerable braking currents.


The ODrive provides a connection for a load dump resistor. I’m not exactly sure how it’s programmed right now but you can use that resistor to help dissipate reverse current during braking. @madcowswe should be able to explain whether or not the brake resistor is setup to avoid over-voltage or not.

Batteries are fine, caps are probably better tbh. But just make sure you precharge them to the correct voltage through a resistor so you don’t blow up your power supply.