Smart(-ish) Electric Car Charging

For a while now I’ve been frustrated that the highly capable ‘smart’ electric car charging point installed as part of the Electric Nation research project reverted to ‘dumb’ mode at the end of the trial period. It’s not been too bad because the car has some of its own intelligent charging logic but since moving from the Octopus Agile tariff to Octopus Go (with a rate of 5p per kWh between 00:30 and 04:30 every night) it’s become more important to do all the charging between those times – and I’ve got enough of the API to the charge point working to exercise the control I need.

There’s a separate Technical Article on the details of the Circontrol EVSE API but the following high-level logic is currently working well:

  • The car is configured to charge immediately and at the maximum rate of 32A / 7kW
  • The charge point is normally configured as ‘Disabled’; this state is automatically set at 12:00 (noon) every day
    • This means that the car can be plugged in at any time after that and it doesn’t start charging
  • At the start of the Octopus Go low-tariff period (00:30), there’s a script which runs to:
    • Check there is a car connected to the charge point
    • Change the charge point to the ‘Enabled’ state
    • Run the ‘Remote Start’ transaction to prompt the car to start charging

The result is that – whenever the car needs charging overnight – it can be plugged in at any time of day and it will be fully charged by the morning, using cheap-rate electricity. The charge point is also available to power pre-conditioning of the car and the battery for a morning departure, if that has been configured in the car.

(If the car battery is really low (like less than 10 miles of range) it can take 4.5 hours to fully charge at 7kW, so it’s not quite fully charged by 04:30 when the cheap-rate period ends. The least-bad thing to do is to leave it charging until it finishes, which is probably no later than 05:00.)

Electric Nation Electric Car Charger Installed

As reported previously, my application to join the Electric Nation research trial was accepted a few weeks ago. The eVolt EVSE unit was installed today.

A few of the reports from the Electric Nation project are being published on the Western Power Distribution website, for example this one about Algorithm Development and Testing.

eVolt EVSE unit installed outside

The outdoor eVolt unit has a high capacity 230V mains connection and a wired Ethernet network connection. The two cables run alongside each other which can cause electrical interference but the installer assured me the outdoor-grade Ethernet cable would cope with this – I presume it includes a foil shield.

In addition to the EVSE unit itself (outside) three smaller units were installed inside:

  • A small distribution board containing a 63A 30mA RCD, a 40A MCB for the eVolt unit and a 6A MCB for the power supply to the comms units (top-centre in the photo below, labelled DB/1B)
    • While the EVSE is rated for up to 32A, I’ve heard elsewhere that no MCB likes running at its full rated capacity for long periods so it’s correct for the MCB to be rated a bit higher
  • A CrowdCharge device which provides some of the remote control functionality for the trial (bottom-right in the photo below)
    • I haven’t studied this in detail but the box contains two boards, one of which seems to be a multi-port Router (it has a MikroTik MAC address) and the other is presumably some sort of single-board-computer
    • Each board takes a 5V USB power supply, hence the two USB leads
  • A hard-wired twin-socket USB power supply (with its own fused spur) for the CrowdCharge device (bottom-left in the photo below)

Electrical supply and communications units inside

I already had a spare Ethernet network socket near the distribution boards to provide a hard-wired connection for the CrowdCharge device; if that was not available they would have installed a WiFi Bridge unit as well.

I’m well aware that the electrical installation at Marsh Flatts Farm is somewhat more complex than you’d find in a standard house so I was very careful to explain exactly what it consists of in the self-survey response. Despite my best efforts the engineers at the installation company had missed the fact there are 4 distribution boards (consumer units) in total and the installer was concerned about not having 32A of headroom from the 80A supply so the EVSE has initially been capped at 16A.

The installation company is going to send me an OWL monitor so they can check how much of the 80A I’m normally using.┬áMy own monitoring shows there’s never less than 40A spare so that should be a formality. Once they’re happy, the EVSE will be remotely re-configured to supply up to 32A as originally intended.