Curtis inverters
Using a Curtis invereter with a Lithiumate Lite BMS.

The Lithiumate Lite may control a Curtis 123x motor inverter either though wire control or through CAN messages.


The Curtis motor controllers do not provide isolation between the high voltage battery and the low voltage circuits.

This poses a significant risk of shock and of likely damage to the low power electronics by way of a single unintentional short circuit.

This proposed ciruit adds isolation to the Curtis motor controller to improve safety.

The system has a traction pack and an auxiliary 12 V battery.

The ignition switch is on the 12 V battery, not the traction pack.

When the ignition is on, and if discharging is OK, the Lithiumate Lite master turns on K1, which powers the Curtis inverter, from the traction pack to the KSI input.

The Lithiumate Lite master limits the discharge current through its Throttle Reduce analog output, by shunting the output of the throttle.

It disables regen current through a relay driven by the Charge OK output, by disabling the brake.

Isolation is achieved by:

  • The DC-DC converter is isolated
  • The Throttle Reduce output in the Lite is isolated
  • Relay K1 isolates Key input of the Curtis
  • Relay K2 isolates the brake input
Schematic diagram


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Page published on: Nov 08 2019.      Installation manual