The goal of the REV2 Pre-Charge system is to protect the motor controller from the in-rush current during the initial ignition of the bike. With a sudden large difference in voltage coming from the battery pack to the motor controller the risk of this in-rush current causing heating issues becomes a main concern. The Pre-Charge on its most basic level acts as a large resistor to restrict the amount of in-rush current to the motor controller to reduce high voltage power from entering, which then charges the internal capacitors of the motor controller. These charged capacitors lessen the energy difference between the battery pack and motor controller, which reduces the chance of inrush current.
This system makes use of two separate circuits; a 12V low voltage control circuit, and a 400V high voltage main power control. Once an ignition signal is received the Pre-Charge system begins receiving the 400V high voltage from the battery pack, eventually the motor controller will send a signal to the pre-charge to begin entering the 12V low voltage control-circuit. The low voltage circuit is responsible for controlling the timing of signals coming from the REV2 handlebar. The high voltage power side is controlled by one signal coming from the motor controller, which is dependent on the low voltage side working as intended. In addition to this functionality the Pre-Charge system also receives inputs from other devices and outputs them to their corresponding systems.
400V Initial Input
Once ignition of the bike has been started 400V is applied to the Pre-Charge, to ensure the safe transfer of current to the motor controller the Pre-Charge applies a resistance large enough to lower the current to a safe value and ensure the instantaneous power is never too high for the motor controller to operate.
This current then charges the internal capacitors of the motor controller to further ensure that the energy difference between them and the battery pack is similar to reduce the chance of in-rush current.
12V Output
Once the PRECHRG_DONE signal from the motor controller is received as a high value the Pre-Charge (In reality a low signal, but input is inverted) will shift functionality to a 12V power supply to the motor controller. This 12V low voltage control circuit manages the timing of signals coming from the REV2 handlebar.
All Signal Relays
The Pre-Charge system additionally functions as a way to send and receive signals from multiple parts throughout the REV2.