Remotely monitors and controls a Mercedes-Benz Wallbox Home EV Charger via The Things Network(TTN) LoRaWAN. It can be used to reduce EV running costs by scheduling EV charging when off-peak electricity rates are in place and where the EV does not support time-based charging triggers.
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This monitor allows Home Manager to interwork with an EV charger over LoRaWAN via The Things Network. It can monitor the state of the EV charger, as well as performing lock outlet, unlock outlet and reset charger commands using the EV charger's Modbus RS485 interface (* See note about downlink command timing). The Things Network is used to support charger locations that aren't able to provide wifi coverage (e.g. in a basement garage). It requires customised TTN payload formats that can be found here and the setup of a mosquitto bridge on the Home Manager side of the system.
- Note that the TTN functionality provides timely uplinking of charger state data, but downlink data (i.e. commands to the charger) are only sent after an uplink message. Therefore commands to the charger are not sent immediately and will be delayed. This does impact the functionality, but it's been minimised by varying the state heartbeat frequency, based on the charger state.
The monitor uses a Pycom LoPy4, Pycom Expansion Board 3.0 and a Sparkfun BOB-10124 Transceiver Breakout for RS485 Modbus communications(P3 to RX-1, P4 to TX-0 and P8 to RTS)
This project should only be constructed and deployed by a licenced electrician and its use might void charger and vehicle warranties. See LICENCE.md for disclaimers.
The system can sense the following charger states:
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"Not Connected": The EV is not connected to the charger. Charger state heartbeats are sent over TTN every 2 hours when in this state.
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"Connected and Locked": The EV is connected to the charger and the key switch on the charger has not been turned to start charging. Charger state heartbeats are sent over TTN every 5 minutes when in this state.
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"Charging": The charger is charging the EV battery. Charger state heartbeats are sent over TTN every 15 minutes when in this state.
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"Charged": The EV is charged to the required level. This state is normally triggered by the EV advising the charger. Charger state heartbeats are sent over TTN every 30 minutes when in this state.
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"Disabled": The charger has been set to "Lock Outlet" or "E0" mode and is disabled. Charger state heartbeats are sent over TTN every 15 minutes when in this state.
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"E2": Not currently used but allows for future maintenance activity enhancements (e.g. setting Device ID).
The system has the following control functions (* See above note about command timing):
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"Reset Charger": It's found that this can be used to commence EV charging when the charger is in the "Connected and Locked" state - even if the charger's key switch is still in the locked state.
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"Lock Outlet": Places the charger in an error mode (E0)and interrupts the charging process. This shouldn't be necessary because the EV will stop the charging process when the desired charge level is met.
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"Unlock Outlet": Takes the charger out of error mode (E0).
ACKs are uplinked via TTN when each control command has been received.
There's the potential to add Status Report and Serial Number/Device Type request commands in the future.
The charger states can be monitored and charger commands can be sent by using the Apple Home App and Home Manager. They can also be used to schedule charging times to benefit from time-of-use electricity tariffs, through an Apple Home App Automation. Other monitoring and control apps could be developed by using the TTN API(mqtt).
This project is licensed under the MIT License - see the LICENSE.md file for details
The project has been developed after exploring some of the charger interworking functionality documented in https://github.com/cvvmedia/symcon.cvvmedia.ablchargepoint. The outcome, combined with my additional protocol analysis is here.