ZEVA Smart Precharger Staged automatic precharge for motor controllers

Motor controllers for electric vehicles typically have a large internal capacitor bank on their input with very low ESR (Equivalent Series Resistance). As such they require inrush protection when first powering up to prevent a large current spike which can damage components – most commonly, welding contactors shut or blowing fuses.

The ZEVA Smart Precharger is designed to offer a 2-stage soft start for motor controllers, limiting inrush current via a resistive circuit to charge up the internal capacitors before automatically closing the main contactor when the process is complete. It can also detect faults and safely discontinue precharge if it fails to start correctly (usually due to an external wiring fault or no battery voltage), or fails to complete within 5 seconds (usually due to unexpected loads after the main contactor).

The precharger is available in three different resistances, to suit three different voltage ranges, as below. (Normally, select the lowest resistance that will work with your pack voltage.)

50ohm, recommended for 12-160V nominal battery packs
100ohm, recommended for 120-240V nominal battery packs
200ohm, recommended for 200-350V nominal battery packs