Our Vehicle to Home (V2H) Experience - Part 1
By Chris Gilbert
Today a nice engineer from ChargedEV called Steve fitted us a V2H charger. This is part of the world’s largest trial of Vehicle-to-Home bidirectional chargers being performed by Indra in the UK.
What’s a V2H Charger?
A conventional EV charger is one way - it takes the electrons from the grid and puts them into your car. A bidirectional charger on the other hand, not only lets you push electrons into your car, but also to pull them out again.
As if you had a giant power bank parked on your drive, your car can used store the electrons, to use them later. This means you can take advantage of time of use tariffs, such as the several provided by Octopus Energy (our current provider), and reduce your electricity bill.
On the more advanced side, you can also sign up to an export tariff, and export to the grid when it most needs it, reducing carbon emissions and earning back money off your bill.
What’s the difference between V2H and V2G?
All the V2{X} concepts involve a similar type of bidirectional charging. In this case, the idea is optimise providing the power to your own home (H) rather than the grid (G). However, the charger will still export excess power to the grid, and you can choose to set it up that way if you wish.
Another type of V2X is V2L (Vehicle-to-Load) which is a simpler form of bidirectional charging, allowing you to plug appliances directly into your car, rather than powering your whole house.
Can my electric car do this?
Maybe. At the moment it’s only supported on the CHAdeMO charging standard, and Nissan vehicles which use this. It’s because bidirectional charging has been long supported by the CHAdeMO protocol, but until recently, not by CCS, which is a newer connector type used by most cars.
The good news is, bidirectional charging is being developed for CCS, and Indra are already working on it for their chargers. There are a few cars that support V2L, such as the Kia Niro EV6 and the Hyundai Ionic 5/6, along with many of the pickup trucks like the Rivian R1T and the Ford F150 Lightning. These are aimed at doing things like running power tools, rather than your whole house.
I have also recently heard about a new trial by Easee and Polestar in Gothenburg, Sweden, where they will be trialing V2G.
How It Was Fitted
We had quite a challenging cable run, because our consumer unit is under the stairs in the middle of the house, and we have had an extension built to the side which has added a doorway.
To avoid clipping an ugly cable to the internal wall, Steve managed to figure out a route into the wall cavity, then up under the floor in the upstairs bedroom, before exiting through the front of the house above a flat roof.
Earth Spike
The charger needs an earth spike to be installed, which is a 2m long copper rod that is driven into the ground. This is because the charger needs to be earthed to the same potential as our other car charger, in case there is a fault and person is touching both chargers at the same time. Without the same potential, in the event of a fault, a person’s body could complete the lowest resistance circuit, (which would be bad).
Removal of Metal Light Fittings
To install the charger, I also had to replace some metal light fittings on the front of the house with polycarbonate ones. This avoided another potential earth difference between those and the new charger.
Floor Run
The cable was run under the floor in the upstairs bedroom, and then out through the front of the house, above a flat roof. This was to avoid having to clip the cable to the internal wall in our new kitchen extension, which would have looked ugly. Steve managed to find an old disused cable run, and used that to pull the new cable through the wall cavity into the bedroom.
Cable CT Clamp
The charger reads the household electricity and solar generation using a CT clamp. This is a device that clamps around the main incoming electricity cable, and measures the current flowing through it. The charger can then use this to calculate the power being used by the house, and the solar generation. This is used to optimise the charging of the car, and to avoid exporting power to the grid when the house is using it.
Type B RCD
The charger also needs a Type B RCD to be installed in the consumer unit. This is because the charger is a high current DC device, and the RCD needs to be able to detect DC faults as well as AC faults. This is a bit more expensive than a standard RCD, but is required for safety, as type A RCDs will not detect DC faults beyond a certain current.
Here, Steve moved our existing PodPoint charger into the new consumer unit, along with a new circuit for the V2H charger.
Ethernet Connection
The charger also needs a physical ethernet connection rather than Wifi, so Steve ran another cable around the front of house and in through the same point as existing Sky and Virgin Media cables. This could then connect to a switch near our TV and avoid potential of WiFi dropouts disrupting the charger.
Indra Smart Portal
Following the installation of the charger, we configure it on the Indra smart portal. This is a web app which lets us set several schedules and manual options.
The charger runs in the following modes:
| Charge Mode | Behaviour |
|---|---|
| Charge | Charge the car battery using the relative rate you set in the portal. |
| Discharge | Discharge the car battery to the house, using the relative rate you set in the portal. |
| Load Match | Try to match the usage of the house by discharging the appropriate amount from the car battery, to keep the usage from the grid close to zero. Any excess solar will be used to charge the car. |
| Export Match | Any excess solar will be used to charge the car at the same rate as available, but no discharge from the battery will occur to reduce use of the grid. |
| Boost | Charge the car immediately, using the maximum power available from the solar panels and the grid. |
| Inactive | The charger will remain idle. |
In addition, it’s possible to select from fixed schedules to switch modes at various times. I settled on a 3H charge at 2am, and load match for the rest of the time. This means that the car will be charged to 100% by 5am, and then the charger will try to match the house usage for the rest of the day.
This should mean that the car is charged to 100% every day, and the house usage is kept close to zero whilst the car is plugged in. Any excess solar will be used to charge the car, and any available car battery will be used to power the house.
In practice, we’ve found it’s quite easy to run down the car battery to 30%, which is the minimum allowed by Nissan. The car charges to full again within 3H though, so is generally close to full by the time we need to use it again in the morning. As such, we are using any leftover energy from each day to support the needs of the house in the evening, when we use the most energy, and when the grid is the least green.
What’s Next?
I’ll add a few subsequent posts on our experiences and looking at whether we’ve saved money or reduced the carbon emissions on the grid by using our car in this way. Hope this post was interesting and useful!