Peter's Blog

EV Update for Electric Geeks!

Written by Peter Johnston on .

This week has been rather trying with a bug progressing through all the kids. I have not had a day without at least one of the kids at home, and three days with two kids in their beds. Carolyn and I are anxiously hoping we manage to avoid the lurgy. After visiting one of the other congregations this morning to do an inspection of their records, I received yet another call from the school to come and collect one of the kids. My plans for this morning have gone out of the window, so having an hour I didn't expect, I thought I would bring you up to date with my electric car ownership.

Warning: this is a geeky blog post! If you don't know your kW from your kWh then this will either be enlightening or like walking into a secret ritual in a foreign language, a complete mystery. 

I am still very much enjoying electric car ownership and the very different considerations and concerns are still quite fascinating, but I have become very aware as you may have noted from my second video that I had some question marks over the speed of some of the rapid chargers that I have used. Getting more and more concerned about this because of the huge importance of these rapid chargers to Scotland's charging infrastructure and the ability to travel long distances across the country, I decided to do some experiments to measure as well as I could the charge rates of various chargers. The video above shows two of those experiments. 

A second YouTube video available here shows the third experiment conducted with a fellow EV driver and his Nissan Leaf which rapid charges using the DC connector on rapid chargers (I use the AC side with my Renault ZOE - the two cars work quite differently for rapid charging).

Having taken measurements while doing these charges, and with the benefit of another ZOE driver in England who did the same thing using a different rapid charging network (a combined Ecotricity/Renault/Nissan network that is expanding along trunk routes) all my anecdotal worries were found to be entirely correct.

I wrote a full report on this yesterday which has been forwarded to Transport Scotland (who funds the charging network), Aberdeen City and Dundee City Councils, and APT the manufacturers of the rapid chargers. 

What I found is that the chargers are working at less than half capacity, meaning the rapid chargers charge cars both on the AC and DC connectors much slower than they should, and slower than specified by Transport Scotland in their guidelines from which contracts by local authorities are created. Indeed, I found that some of the much cheaper "fast" chargers (providing 22kW) actually charge my car more quickly than the "rapid" chargers that should charge in half the time with their 43kW supply. The actual figures I found were 20.9kW for the fast charger and 17.8kW for the rapid charger.

Comparing State of Charge over time with rapid and fast chargers

This chart shows this difference. The interesting part is the part up to around 90% state of charge on the battery. The final 10% is always much slower, so for these purposes it can be ignored. During the main charging phase, you can readily see that the less powerful charger (22kW) is charging the car faster (steeper angle on the graph) than the 43kW charger.

Compare this to the charge rates on an Ecotricity rapid charger (also rated at 43kW for AC charging) as recorded by another ZOE driver in England on five different visits to these chargers in one day (he was on a mammoth 300 mile trip).

Renault ZOE charging at Ecotricity rapid chargers

This chart shows that the car was receiving around 40kW during the main charging phase. This is more like it. It follows my experiences of the Ecotricity chargers I have used at Ikea in Glasgow and at Bothwell Services on the M74. At one of these chargers I was able to charge from 3% to 100% in a little over an hour. That would take around two hours minimum on one of the APT chargers, though they supposedly provide the same power output.

If you are on a journey say from Aberdeen to the West end of Glasgow during which you need to make two charges along the way, you can see how the differences in charging rate will make a big difference to the journey time.

More worrying still was when we tried charging both my Renault ZOE and a Nissan Leaf at a rapid charger.

Comparison charging Renault ZOE and Nissan Leaf on APT rapid charger

This chart shows the kWh of energy provided by the charger over time. The reason much more energy was provided to the ZOE was because my battery was more empty to begin with and I let it run on until it was 99% full. The Nissan Leaf by comparison was around 30-40% full (it had two bars on its battery meter, it does not give an exact %) and the charger automatically stopped charging the Leaf when it got to 80% full as a protective measure for the battery. Nonetheless, the power provided during the main charge cycle can be calculated and for my ZOE was about the same as when I charged alone, at 17.6kW, still woefully short of the expected 43kW. The Leaf, however, was being provided with around 11kW. This is almost a fifth of the expected 50kW on the DC side. There is something very wrong here.

Because we are all paying for this infrastructure to go in as it is government funding that is enabling local authorities to create these charging networks, it is only good stewardship of these resources to ensure that they are working as specified. This is not the case at the moment.

Alan Simpson from Aberdeen City Council who is very proactive and keen to support EV drivers, and whom I cannot fault in his communications with us EV drivers letting us know about issues, met with us as we carried out this last joint experiment so that he could see hands-on what is going on. 

I am hopeful that APT will get pressured to do something about this. 

So, that is my update on EV ownership and the public charging network, which is still very much in its infancy. There are growing pains at the moment which make undertaking longer journeys unnecessarily slower than they should be. Thankfully my local charger at Duthie Park has not let me down yet. 

All this is giving me some pause for thought in deciding which manufacturer of charging points to approach for the installation of a charging point at the church, that is for sure.