Part 5 in Peter Aubourg’s Diary of an EV Driver

I finally bought a charger that will lap up my excess solar power. This power would otherwise be exported back to the grid for a paltry sum. My wife said that I am determined to get free fuel for the EV no matter how much it costs. That’s a bit harsh!  I have calculations and spreadsheets. Trust me, I’m an engineer.  It will be a thing of beauty and a joy forever. Well, at least for a long time.

The day came when the installation was complete and time to do some testing. It was a dark overcast day, so I could not do any “Solar Divert” testing.

So instead, I tested the charger at its full rate of 7 kW, drawing power from the grid.  This was much faster than my 1.6 kW trickle charger. I could fill the battery from 10% to 90% in less than 6 hours. With this test, I had to pay for the grid electricity, but it is still much cheaper than petrol. But what I am really after is free fuel.

The next day was overcast to start but by mid-morning it was clear. The charger tracked the excess solar generation like a treat. When the clouds cleared, the charger would gently increase the charging rate to match the increased solar generation, so that the excess power went straight into the car battery.  It continued to do this balancing act, so that no power was exported or imported from the grid.

When the clouds started to come over, the charger would decrease its charging rate to the car so that this “no import or no export” from the grid was maintained.  It also continued the balancing act when our hot water heater came on in the middle of the day as it is timed to do, sucking up a big chunk of our solar power.  The charging into the car dropped down so that there was no imported power from the grid.

A big success!

I am noticing that solar radiation is much greater than you would expect on days that are overcast but still fairly light.  I suppose that stands to reason, when you think of how unexpectedly sunburned you can get on such days. These days are great for the solar divert system. The reflected light from the clouds continues to generate power from the panels, for a while, even when the sun goes behind the escarpment.

So, I now have it. A solar-powered car with zero fuel cost! The charger was worth it … Definitely.

And my wife likes it as well.