The sun powered car

Stuart has had a fully electric car, a Renault Zoe, since December 2018. This has a 40kWh battery which gives it a nominal range of around 180 miles on a full charge. We find that, in the Summer, we get 180 miles or a bit more pretty reliably, but in the Winter it drops to 150-160 miles and can go down to 130 miles in really cold weather. Remember that Lithium-ion batteries are chemical devices and therefore temperature sensitive! They work best at about 30C and become less efficient at low temperatures.

We charge the battery using the solar panels on our roof. We find that between about mid-Feb and the end of October we can usually keep the car fully charged without importing power from the grid. During November to February we don't always manage to generate enough, especially if there are prolonged periods of dull, overcast weather.

When we bought the car, installation of a charger was included in the price. This would have been an  unsophisticated device from Charge Master which only has one option: plug it in and it charges at 7kW. If we had gone for this, they would have claimed the Electric Vehicle Homecharge Scheme grant of £350 on our behalf. We decided to install our own choice of charger - the Zappi from MyEnergi - and claimed the grant ourselves to put towards it. The Zappi is designed to work with micro-generation systems whether solar panels, wind generators or hydroelectric. It has three charging modes:

• "Fast" - charges at 7kW, importing from the mains as necessary (though of course it will use anything you are generating as the Charge Master would have). At 7kW, our battery would charge fully from empty in about 6 hours.
  
• "Eco 2" - charges only using the excess power you are generating and would otherwise be exporting to the grid. You must be exporting at least 1.5kW for charging to occur. This is the minimum charge rate that EVs are designed to accept. If you are exporting more than this, then it will all be used to charge the car's battery up to the Zapp's maximum of 8kW.
  
• "Eco 1" - charges at least at 1.5kW. If you are exporting less that this, it will import what ever wattage is necessary from the grid to make it up to 1.5kW. If you are exporting more it will simply use all of it to charge the battery - just like Eco 2.

We keep the Zappi in Eco 2 mode pretty much all of the time, so whenever there is enough sunlight and the battery is not already full, the car will be charging. If we really need to have the car charged at a particular time for some reason and are not generating enough (most likely in mid-Winter) then we use Fast mode overnight.

The bottom line is that a reasonably sunny morning in the Summer will power an average local birding trip of around 50-60 miles.