Should I connect the driver directly to the battery terminal?
Yes, the supply line of the motor driver should preferably be taken directly from the battery terminal; long, shared lines in between create voltage drop and interference. Put the fuse at the point closest to the battery terminal. At 12V a 3% drop is only 0.36 V, so cross-section and connection quality are decisive.
The reason for connecting directly to the battery is voltage drop and noise isolation. If you feed the driver through the vehicle fuse box, a long distribution bar or a line shared with other loads:
- The supply voltage sags during the starting pulse; the starting current is typically 5-8 times the rated value.
- Other devices sharing the same line are affected by that sag.
- The noise produced by the motor current is carried to sensitive devices over the common line.
Correct practice:
- Run the positive and negative lines directly from the battery terminals.
- Place the fuse at the point closest to the positive terminal; what is being protected is the entire cable in between.
- Choose the cross-section according to the peak current (KS250 45 A / 5 s, PT500 40 A / 15 s) and verify the voltage drop by calculation.
- Do not rely on the chassis and run a thinner negative line; run it separately and thick.
- Tighten the battery terminals and the connectors to their torque and check them periodically.
A battery has one more advantage: it can absorb the energy coming back from the motor during deceleration. Because switch-mode power supplies cannot sink current, the line voltage climbs rapidly in the same situation.
The full topic: DC Motor Driver Selection Guide