Smart Precharger


Download design files:

Files are provided under the open source MIT License.
A copy is included in the ZIP archive.


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 two different resistances, to suit different voltage ranges, as below. Custom resistances can also be provided by request.

50ohm, recommended for 12-180V nominal battery packs
100ohm, recommended for 180-360V nominal battery packs

Related Products

MC600C Motor Controller   $1,595.00
150V 600A motor controller for Series DC and PM DC motors. For EVs up to approx 1000kg.

MC1000C Motor Controller   $1,995.00
150V 1000A motor controller for Series DC and PM DC motors. For larger EVs, higher performance and direct drive vehicles.


Power supply: 8-18VDC (12V nominal, 3A max)
Typical precharge time: 1-2 seconds
Internal coil spike suppression diode
Dimensions: 71x25x18mm

Datasheets & Manuals:



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