Smart van automation remotely running fan

[Unclebob]

I've been doing smart home automation for a while now, mainly using MQTT, Tasmota, and Home Assistant.
My van is now about to get the same treatment - I've got a Teltonika RUT955 4g router which is the brains of the operation, providing an MQTT broker and VPN to my home assistant server back at home. Plans so far (which I know how to do) include monitoring and charge management for my leisure battery and removable battery bank, manage auto stop/start, open/close windows, lock/unlock with phone or NFC tags (keep a tag permanently in each wetsuit and maybe leggie as a backup when I go surfing), temp/humidity monitoring inside. In future I might look into logging/monitoring via the CAN bus, but that's a low priority for now.

One thing that I'd really like to do is control the interior fan when the car is off so I can have it suck in some fresh air when parked in the sun on hot days to stop my surfboard wax melting :/ I'm in Australia, so this is a big problem for me in summer!
Does anybody know if there's anything special that I need to do to turn on the interior fan when the car is off? Bonus points for controlling recirc (this would be useful for the dehumidifier to help dry my wetsuit) It's just the simple old resistor pack for fan speed, but not sure if this runs the fan directly or if it's driven by some control unit. I'll be swapping it over to run from the aux battery, so not worried about it running flat (battery charge will be monitored anyway, so planning on having things shut off based on charge level and how much I care about them).

Open to any other ideas you may have as well!

 

[mr.needs]

Sounds interesting, can you share the details on how you will control the auto start/stop as well as open/close windows and lock/unlock?

Plans so far (which I know how to do) include monitoring and charge management for my leisure battery and removable battery bank, manage auto stop/start, open/close windows, lock/unlock with phone or NFC tags

I also have the basic 'climatic' A/C system which uses a resistor pack for fan speed control. There's nothing particularly complicated required to run the interior fan when the car is off.

I set this up when I modified the Webasto diesel auxiliary water heater to be a parking heater. Initially I followed the VW wiring diagrams (below), and took a (fused) power supply from the auxiliary battery, through a relay which turned on when the parking heater is on, and then connected into the 2.5mm yellow/orange wire on the back of the A/C control unit (T5r/2 on the drawing). This is the equivalent of fan speed setting 2. This was ok, but I've since added a temperature sensor and PWM motor controller to be able to control the fan speed automatically to a desired temperature set point. So now the power supply goes from the auxiliary battery, through the motor controller, and then connects onto the 4mm red wire on the back of the A/C control unit (T5r/4 on the drawing).

I live in the Alps, so primary motivation is heating rather than cooling the van. We've had a few hot days this summer, so I've tried running the fan (with the van off) to see if it cools the van. It works ok I guess, but not super effective and it does use a lot of power. I was thinking of adding some control logic, so that if the battery is already fully charged and the van internal temperature goes above a certain limit then it would start the fan automatically, using the excess solar power thats available.

A Raspberry Pi Zero is the 'brains' of my van, which is controlled from the Blynk App on my phone. I have a RS485/CAN HAT that communicates using Modbus with the Renogy battery charger, and using CANBUS with the Webasto parking heater. I also have a Chinese fridge which is controlled using the Pi's built-in Bluetooth. And I control the LED lighting dimming using its PWM outputs.

 

[Unclebob]

Sounds interesting, can you share the details on how you will control the auto start/stop as well as open/close windows and lock/unlock?

Hey, sorry I missed this before.

Thanks for the info. Sad to hear about the power usage on the fan, but I suppose it's designed for use while driving when power is not such a concern. I may look into other ventilation options, but I'm limited in terms of what I can do height wise due to my garage (and I think the maxx air fans that everyone has here look butt ugly!)

What RS485/CAN hat do you use? The rs485 comms on the Teltonika router are... Not great. I'm sure it'd be fine once you get it going, but there's no log - it just works or not. Not great for troubleshooting. This is probably a better option. I'd be interested in what software/config you're using to communicate with the battery as well!

Start/stop switch has a red backlight, a yellow light indicating it's disabled, and a wire for the actual (momentary) button. Basically just going to have a sensor input attached to the the yellow light (high = off) to sense the mode, then throw in a relay to "press" the button. Initially it'll probably just do something like turn it off when I turn the car on, and I can just switch it on if I hit heavy traffic, but in time i'd like it to figure out the distance to the next intersection and disable it if I'm stopped near the intersection (potentially looking for a gap in traffic).

For lock/unlock there's a thread floating around somewhere about adding extra lock/unlock switches. It's basically just a spliced wire & resistor as per that thread, then relays instead of switches.

Windows may be a bit harder since they get disabled when the ignition is off (once you open the door). Starting off, I'll just splice in to the existing switches. If outside temp is > 20 degrees, crack the windows when I turn off the ignition. I have weather shields so this should work fine. Stretch goal is probably introduce my own controller for the windows and bypass the body control module entirely.