Will the driver be damaged if I connect reverse polarity?
On a circuit without reverse polarity protection, connecting the supply terminals the wrong way round can cause permanent damage. The simple protection method is a series diode, but it continuously drops 0.4-0.7 V; at 15-30 A that means 6-20 W of heat. A P-channel MOSFET is a far lower-loss alternative, but a zener between gate and source is mandatory.
Always verify the polarity before connecting. On an unprotected circuit a reversed connection can destroy internal components instantly. Always verify the polarity by measurement before connecting.
Comparison of the protection methods:
- Series diode: The simplest solution. Its drawback is a continuous 0.4-0.7 V voltage drop. It produces roughly 6-10 W of heat at 15 A and 12-20 W at 30 A. In a 12V system this drop is also a serious loss of voltage.
- P-channel MOSFET: The source is connected to the supply line and the gate to the chassis side. Because the on-resistance is very low, the loss is far below that of a diode. However, a zener between gate and source is mandatory: the VGS limits of MOSFETs are typically on the order of ±20 V, and in a 24V system tying the gate directly to chassis destroys the MOSFET. Transients in an automotive environment increase this risk.
Practical measures: colour-code the cable ends, label the terminals, measure the polarity with a multimeter before connecting, and leave fitting the fuse as the very last step of the installation.
The full topic: DC Motor Driver Selection Guide