Since this vehicle is supposed to be a practical daily driver in the summer, air conditioning is going to be a must. The RX8 has an AC compressor, but it is belt driven and clutch engaged. Belts don’t work with my design criteria of limited to no maintenance and engagement clutches just waist a lot of 12V power to lock the pulley to the shaft. Even if I were to hook up another motor to drive the compressor, it would need to be capable of about 4KW (over 300A at 12V) This would require a HUGE wire and drain my 12V battery in minutes (if not seconds)
Because of this I decided that I needed a high voltage compressor and that the RX8 compressor was not the correct path to take here. This means that I need to find an AC compressor from a production electric vehicle, and on top of that, one that has already been reverse engineered so I actually know what CAN messages to send to get it to turn on. I decided to go with the Ford Azure Dynamics Compressor because some people over on the EVTV forum have already made some great steps to figure out the CAN messages needed. I then turned to eBay and luckily for me I managed to find a brand new unit at a pretty good price.
Controlling the Azure Dynamics Air Conditioning Compressor:
Thanks to Weisheimer from the EVTV forums for this one. The data below is the direct control of the compressor and the signal table below is the full list of CAN messages used for the HVAC system in the Ford/Azure Dynamics vehicle that this was designed for.
The Compressors ID is 0x439, and is an output for various compressor status messages.
The compressor is controlled by can ID 0x410. Below are the key messages controlling the compressor.
SIGNAL NAME ID Start Width Res Offset Sign Min Max Unit
target_compressor_speed 410 8 8 60 0 F 0 15180 rpm
max_pwr_consumption 410 0 8 0.1 0 F 0 25.3 kW
compressor_on_off 410 46 1 1 0 F 0 1 Boolean
CASS_on_off 410 43 1 1 0 F 0 1 Boolean
warmup_cycle_cntr_incr 410 41 1 1 0 F 0 1 Boolean; sent by the compressor
COMPRESSOR_STATUS 439 56 2 1 0 F 0 3 enum
ACTUAL_COMPRESSOR_SPEED 439 48 8 60 0 F 0 15180 rpm
ACTUAL_POWER_CONSUMPTION 439 40 8 0.1 0 F 0 25.3 kW