Purpose

MSXI had many issues with its LV system. They can mostly be categorized into two systems: power and signal.

Power Distribution

1. Not enough granularity on LV power control resulted in powering too many things off the auxiliary battery.
2. Current capacity of the M12 deviceNET cables was a concern.
3. Running the horn off the main auxiliary battery may have drained it prematurely.
4. The lack of a monitoring system for the auxiliary battery prevented us from noticing the state of the lead-acid until it was completely dead.

Signal Distribution

1. Bad organization of external signals (should be delegated to specific boards)
2. Boards were assigned to boxes without considering physical limitations and interfaces
3. Killswitch was primarily software-controlled - should've been mechanical

Solutions

Power Granularity

There are regulations on what can be powered from the auxiliary battery. At most, we should be powering the power distribution board, main battery relay (temporarily), driver ventilation?, and the BPS. If the BPS faults, it can additionally power the battery ventilation fans and trip indicators.

Since our primary trip indicator is on Themis (over CAN), we need to keep Themis active on faults. Unfortunately, the motor controllers are also powered alongside CAN. Since they draw around 500mA each, we should be able to disable them or only power them off of the main battery.

Other LV power systems (ex. rear-view camera) should be powered on a separate line.

Current Capacity

Note that splitting the power distribution into multiple dedicated lines will help with current capacity issues.