PC.v2

Project Definition

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.

The functionality and timing of this board has always baffled EVT members (including the people who made it). The main reason for this is because the schematic in Altium is a 1-to-1 recreation of the recommended pre-charge implementation in the motor controller data sheet. This recommended setup did not have amazing documentation to start with. To prevent further confusion, the following list shows every step of the pre-charge sequence in order:

1. The Main Switch (big red switch) is closed. This supplies 400V to the LVSS and to the pre-charge high voltage circuit. The yellow relay prevents 400V power from leaving the board.

2. LVSS creates 12V, which supplies low voltage to the pre-charge board and handlebar. 

3. 12V is applied to RLY3 (which is a signal going to motor controller), and to two pins on the small black relay. This 12V relay is active low, so for now it is open. 

4. The rider turns the key on the handlebar. 

5. This turns on the IGN signal, which passes through the pre-charge and goes to the motor controller. Some of this power is bled off to BATT+ through diodes (why this is done is unknown)

6. MC receives the IGN signal, and pulls RLY3 low. This consequently pulls the 12V relay control pin low, which closes the relay.

7. Full 12V power is now applied to BATT+. This is the motor controller's "main" 12V supply. Once this is active, the motor controller will wait for the START signal

8. The rider pushes the small square button on the handlebar, generating the START signal (which is just a pulse). This also passes through the pre-charge board, without affecting anything on the PCB.

9. The motor controller receives this pulse, and generates a signal to be sent to the 400V yellow relay (This is also called START on the pre-charge board, which is misleading).

10. The yellow relay closes, supplying 400V power to the motor controller. This is where the actual pre-charging finally starts.

11. Once the MC capacitors are fully charged, the yellow relay is closed by stopping the signal sent by the motor controller. 

12. The MC then generates a different signal to close the high-side contactor (internal to the penthouse). At this point, the full voltage and current is being supplied to the motor controller.

13. The pre-charge process is now finished. The motor should now spin when you turn the throttle. Hooray!

Some additional notes are included below:

• It needs to be stressed that the pre-charge PCB sits in parallel with the High-Side contactor. This is why the high-voltage side has 400V in and 400V out. 

• As mentioned in the steps, the label for the signal that controls the yellow relay is incorrect. It should be labelled RLY1 (Pre-charge Contactor Drive)

• REV2 currently has no discharge process. To properly discharge the bike, you have to wait up to 5 minutes for capacitors to bleed off stored energy (according to the MC datasheet)

• I have no idea what happens with the pre-charge board once the pre-charge process finishes. Does the MC still get 12V afterward? This isn't that important so we've never looked into it.

OLD NOTES:

On 9/8/18, testing was done for the high-voltage components of the board. A 60V source was used to charge a 440 micro-farad capacitor. Below is the Oscilloscope trace of the charging capacitor, with a rise time of 874 ms. This verifies the functionality of the high-voltage relay