Earth Day April 21, 2018

We decided to have an EV, Plug-in Auto Show, Saturday in honor of Earth Day. We had a Tesla, two BMW i3-REx, and a Prius Prime BUT it was our first attempt. I presented the program.


This chart comes from the USA Energy Information Administration, Dec 2017 for Alabama.

Understand I have no problem with burning coal to make electricity. Rather I think it is wrong to burn coal inefficiently. A simple formula show coals can be burned more efficiently:


The J1772 connector is an SAE standard:


In the USA there are two types of power distribution. Split phase is what is found in the home, neutral is center tapped and two legs. Commercial power can be three phase:

Between L1 and L2 in the home, the unloaded voltage will be 120VAC to neutral and between L1-L2, 240 VAC. In three phase, each leg is 120VAC relative to neutral, a white wire, and due to the phase angle, 208 VAC between any pair of legs.

The pilot signal is how the EVSE tells the car the maximum current, regardless of voltage. At the same time, the car signals to the EVSE that it is there, received the maximum allowed current, and time to enable power to the J1772:

At -12V between the pilot and ground, the EVSE is broken. It may take 30 seconds before the two drops the link with an error. If someone walks away too soon, they won't see the error show but they will find there was no charge.

There is a 1k ohm resistor on the pilot line in the EVSE. The a car plugs in, it has a resistor that reduces the voltage to 9 V. Then the EVSE can signal the maximum allowed current by a pulse width modulated, 1 kHz signal. In the example, 75%. Using the chart it corresponds to ~45A. Then the car adds another resistor to lower the voltage to 6V so the EVSE will connect the power pins to the grid. If the car needs a cools environment, it can lower to 3V so the EVSE garage can lower the ambient temperature.

One issue is many do not know how to answer the question of how much does it cost to drive. The USA EPA provides kWh and gallons per 100 miles. These can quickly give a credible metric of EV versus gas miles, more than 2-to-1, gas over electric:


Now a replacement EVSE can come in different makes and models:

The cheapest is a straight replacement. Although tempting, a dual voltage EVS at 16 A can not be used in the older NEMA 5-15 plug. A better but more expensive solution is dual voltage and multiple current.

An expensive but better approach is a home EVSE with management:

The EVSE communicates with a server that the user can access and manage with either a personal computer or cell phone.

When trying to get a commercial installation, the goal is to make a fair trade. Provide 'free' electricity to pay for the trip down:


Here is an example of typical, PC based management including monthly summary, daily summary, and down to individual charge sessions:


It can also provide performance graphs fo charge over time:

Here we see the smart phone App of the same data.

NOTE: the 211 VAC comes from the JuiceBox which may not be accurate. Open circuit, it shows 212 VAC suggesting a 4 VAC error.

Bob Wilson

ps. The fuel cell advocates did not attend.

 

What happened is I used the voltage read by the JuiceBox 40:

This suggests the problem could be an inaccurate, internal voltage reading. I'll fix the text and footnote the potential voltage reading error, (212-208) / 208 = 1.9%. However it could be normal line voltage variation.

Bob Wilson

 

I did a poor job of publicizing the event so there were two others, Scott, a traveling physical therapist, BMW i3-REx, and a physicist, Tesla Model S, 100D. We also shared what is going on with the staff before the noon rush showed up. But given who was there, I brought up the screen shots from the Model 3 video. The other BMW i3-REx owner has a Model 3 on order and expecting his in the coming month. He plans to do an early lease turn-in and go down with his Dad who is interested in the car.

We also had a chance to discuss our mutual disdain for using "green" because other characteristics are so much better than an ordinary ICE. They are quieter, smoother, excellent acceleration, and low maintenance. In effect, all of the luxury car attributes in a much more enjoyable ride. But there is an underlying concern we share.

An election year, adding road taxes is not popular at the ballot box. But we suspect after November, the Alabama government will come after us 'hammer and tongs' to jack up the EV vehicle registration fee. Without a counter narrative and political involvement, we could see a repeat of the Georgia experiment.

After the meeting, Scott helped me get my BMW i3-REx back home and back to the Prius Prime. We then drove to Whole Foods and spoke with the acting manager. They are working on how to approach getting the repair and I again offered to help (note to self, investigate how to become a licensed electrician.) Scott volunteered the Tesla EVSE program and the manager took down a note. So we'll see if maybe we can get the Nashville Tesla staff to visit and help on an application.

So it was a massive fail on sharing the technology with lay people. We'll have to figure out a better approach. However, we did share our common concerns and that was useful.

Bob Wilson

 

That it why I tried to emphasize the cost advantages. It is hard to argue against a dollar that stays in the wallet.

Bob Wilson