Jump to content
  • entries
  • comments
  • views

PV EV charger control schematic



This is the latest system we have:





There are 4 CT relay clamps, 3 for the EV charging, (and one will be for battery charging), which are set at different PV output levels depending on the month of the year which decides what rate of PV needs to turn on the charging of the EV. This relates to a 3kW charger and the expected power requirement for the EV on a particular month and the expected production using the PGIS web site calculator.


The summer 3.6kW rate is because the house typically uses about 0.6kW and during the summer there are plenty of hours when the power is over 3.6kW.


There is of course an override for when we will charge irrespective of the PV supply.


When the mains option is chosen a red light indicates this choice.


When the car is being powered the green light indicates this.


The theoretical result is not as good as I hoped as M2 relay is time delayed to stop the charging going on/off quickly during cloudy/sunny days, and because of the lack of supply during deep winter, however for 4000miles we hope to use about 730kWh PV and buy 70kWh from the mains.


This will improve if we manage to obtain a bigger power storage EV as the PV history for hear over the last 15 years shows good days are usually grouped together meaning during winter we might not have used up the power in EV before another glorious day comes around and then have a week of cloudy weather.


The only works because the car is plugged in to the EV charger most of the day time. (like today).


I'm hoping someone can use this to help them develop a similar system. 


If you need any info on the parts are, ask.


Good luck










Recommended Comments

Great work, would love to see a photo, could also be used for bringing in different heating loads too to supplement shoulder season.


great job and it’s relay based which I like!!

Link to comment
1 minute ago, TonyT said:

Great work, would love to see a photo, could also be used for bringing in different heating loads too to supplement shoulder season.


great job and it’s relay based which I like!!

Hi @TonyT


It may be relay based but the whole system (MVHR, Hot water, ASHP central heating, day storage heaters, EV charging and PV monitoring, with battery back up still to do) is now about 120 wires, 12 switches and 20 relays.


I am still designing and writing up the shoulder season heating which is run off our Solic 200 at the moment, however this will take a few days. We have 'day storage heaters' relayed after the hot water reaches temperature! Checked this out with the manufacturer and they do the same in their showroom office with an oil heater but I wanted it for the night when paying for the power to the ASHP.




CT adjustable relays showing supply of over 1kW





CT adjustable relays behind protection...



Relays to the 3 CT adjustable relays.






Far MK 3 position switch (K5) to choose EV charging options




Second MK 3 switch (K9) out at the moment: Choosing what level of power to turn the EV charging on with.





Switches M2 and M3 and CT Relay which activates green light when car charging.


All of this could be installed in one box but we have no room and K5 and K9 switches in kitchen for easy access and the rest in utility room all over the place.











Link to comment

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...