Some electric utilities have different rates, one for daytime and a special rate at night. What if you wanted to get your car charged only during the nightime tariff to save cash? That’s what Medium author Pyan Walmsley in the UK did:

We’re in the process of switching to our new energy supplier (Octopus) Electric Vehicle (EV) Tariff. Of which the daytime rate of electric is around the same as other tariffs at 14p per unit, but for 4 hours a night this reduces down to 5p per unit. Roughly taking my yearly charging down from £200 to £70.

In hacking the charger control circuitry:

I then posted on SpeakEV about my postings and within discussion originally looked at connecting my own MCU between the car and evse’s Control Pilot Signal. This is a mixture of resistors to tell the charger if the car can charge or not and a PWM Signal back to tell the car the speed it can charge at.

But then someone said instead of intercepting the signal as I only wanted to control the timing to just connect and disconnect the control pilot. Even easier! Just a simple relay. Throughout discussion someone said the car might throw errors if the CP is just disconnected mid charging.

The solution to this was to also use the lock feature by locking the charger first then disconnecting the CP.

Ok, time to add a microcontroller and relays:

It was then time to implement it, I ordered a cheap 5V Dual Relay module off eBay as this was only low voltage being controlled.

Then the hardest part, what board to use? An arduino was too simple as I wanted it to have connectivity, after looking through my box of boards including Raspberry Pi, Onion Omega, Arduinos of lots of varieties and more I settled on the Particle Photon I have had in its box since backing it on Kickstarter.

The great thing is that it can be programmed via a Web IDE but also has IFTTT integration making it ideal.

Read about the integration and how it worked out in the Medium article. And shop for the Particle Photon here.