# DC power supply for 30A motor driver

I have a 30A 5-30V Single Brushed DC motor driver that will be used with a 12V 30A gear motor.

I have a MegaWatt 36 Amp 12 Volt 13.8V DC Regulated Power Supply that I wanted to use for the driver pwr source. But, I just realized the driver docs say to ALWAYS use a battery as a power source if an inductive load is used.

The docs say that a battery must be used in parallel with the power supply to protect the driver against possible flowback when the motor is stopped.

My question is: can I use a 12V car battery, and simply wire the power supply and motor driver to it, then set pwr supply output to 13.5V? The pwr supply would always remain ON.

They typical way to handle this it to have a resistor bank that gets switched across the input when the voltage rises beyond some threshold. This absorbs the regenerative energy and dissipates it as heat.

If you can quantify the maximum regen energy you will see in your application you might be able to use a capacitor bank on the input to absorb/reuse the energy. But you have to size the capacitors so that the maximum energy doesn't exceed the maximum input voltage (or the rated voltage of the capacitors.)

The battery in parallel with the supply could result in overcharging, so I would not recommend it.

• Im assuming the regenerative energy is the result of continued shaft eotation after the motor is issued a stop. But since this is very low RPM for opening a greenhouse curtain, is this something I really have to worry about?
– dan
Commented Jan 24, 2017 at 22:42
• Not exactly- The motor shaft and load have a certain kinetic energy while the motor is moving. When you command the motor to stop, a large part of that energy is converted back through the motor to electrical energy at the input. (Conservation of energy- If it's not dissipated as heat it goes back to the input.) I have no idea how much energy would be regenerated in your application, but you have to understand it and design for it. Sounds like maybe some capacitance at the input might be sufficient but you will have to determine the amount of C. Commented Jan 24, 2017 at 22:47
• So the answer is either a res. or cap. bank across the input of the motor. If the voltage goes above that of which is supplied by the pwr supply (12v) the switch trigfers dumping the energy onto a heat sync or cap.
– dan
Commented Jan 24, 2017 at 23:12
• The cap bank can be attached at all times (to the input of the driver, across the power supply, not across the motor leads). No need to switch it in or out. The resistor bank would get switched across the supply only when the voltage rises above some setpoint that's above the nominal voltage. Commented Jan 24, 2017 at 23:21
• Since my driver can handle 30v, this would be the threshold for the switch. Thanls for all the help!!
– dan
Commented Jan 24, 2017 at 23:32