EV Charging…First Lessons
On December 5th, I picked up my first car in years, an Electric Vehicle! An exciting new technology and I had lots of questions, from how to charge it to how much it would actually cost to drive. So 20 days later, here’s my first report out on experiences charging it (without a driveway/garage).
I hope this can provide both a non-technical story to answer questions about switching to an EV as well as some detailed data-points for those looking for analytical insights. If you want to just see the insights, jump down to the Lessons Learned section. And if you want the analytical bits, jump down to The Data section.
Note: Edited 1/5/21 to add new charging sessions and clarify another assumption/hole in the date.
Note 2: Edited 1/25/21 to update data on charging…I think the home charging info has stabilized.
Overview of EV Charging Options
When it comes to charging an EV, the holy grail is a quick “fill up" experience the gives the convenience of a typical gas station stop. Speed is of the essence. In the electricity world, speed = power. Power is measured in Watts (W is the unit, kW or MW for higher power ratings). So fast charging (eg higher power) makes the wait time to fill less.
There is still a lot of room for improvement in the EV charging experience. But unlike gas cars that have to fill up at a gas station, EVs have several options. So far, I have tried three different charging methods (referred to as Level 1, 2, and 3). The speeds of charging are approximately 1 vs 7 vs 50 (kw). But that’s a factor of 50:1 between what the fastest charger I have plugged into does and what my house plug can deliver.
There are really different charge times with the different charging options! For the 60kWh battery in the car, that’s the difference between waiting 2 1/2 days for a full charge and less than 1 1/2 hours.
So why not find the fastest charging and go for it?! Well, the other side of the equation is how you get the electricity need for this charging. Usually a utility needs to provide the wires and service for energy. And the service of any customer has a maximum power rating. My house service is not capable of delivering the 50kw of power typical at a Level 3 charger. These power ratings are typical for many commercial customers, who are also familiar with the billing implications. Nearly half of the electrical bills of commercial customers are due to their maximum power usage at any one time, known as “demand charges.” So as a host for EV charging, someone must pay for the cost of the service. Who will that be? In some cases, like the Volta network, advertising can subsidize the costs of offering free charging. In some cases, like in some national parks, there are sponsored charging services. In other cases, the charging is a paid service, and the faster the charging the more it costs, generally.
When charging, there are instances when I want it to be fast (eg mid-point on a trip) and other times when it doesn’t matter (car is parked for many hours). So the choice of charging method and what I want to pay for it is driven by convenience and availability.
First Experiences on Each Charging Option
After picking up the car, my first trip was 43 miles (highway) and car reports 124 miles of range. It seemed to go down faster than expected (due to lack of recharging on highway driving), so to try out charging, I stopped at a Whole Foods that had available chargers. First fast charging experience! The EVGo chargers provide a fast charge (up to 50 KW) and supposedly are powered by renewable energy. I opened the EVGo app, started a charging session and headed into the store. Easy peasy and a little over a half our later, the app tells me I have added 16.5kwh (a quarter of a “tank”). Battery now reports 185 miles of range.
Wait…this was sold as a 50 KW charger and I got much less than that (~29KW). Since the service is billed by the minute and not the amount of energy delivered to the battery, I overpaid for what I thought I was getting. Apparently, that’s a feature, not a bug, according to EVGo.
To be fair, my wife charged at an EVGo site from a near empty battery and it cost about the same…but I don’t have any data on that, so…cliffhanger for now!
Next, I tried three different Level 2 chargers, which deliver 6–7 KW. These three chargers were conveniently located at places I was going, including a park and a grocery store. Unfortunately there were issues with availability and whether charging worked or not at two of the three places, so less charging that I had hoped for. Also harder to track the time and energy delivered on these units. Nonetheless, free charging was appreciated!
With about 1/4 charge in the battery and little need for driving for a few days, I managed to get a street parking spot in front of the house! Commence Level 1 charging (aka dangling a long extension cord out a window to charge the car from a normal plug). Though slow, this worked. It took just over 48 hours to fill the remaining 3/4 of the battery, interrupted briefly by a street cleaning move. For the first time in three weeks, the car battery was full!
Lessons Learned
Initial lessons are:
- Charging changes based on how full the battery is. Charging happens faster when the battery is near empty and increasingly slow as it close to full. This seems to be built into some chargers as well as the car itself.
- Charging from a home plug without a garage is possible! This was a surprise for me. With patience, even the standard electrical outlet can effectively charge the car.
- Apps are very useful in finding charging places! So far PlugShare has been the most useful.
- Free options exist and paid options can quickly get expensive. In fact, my first Level 3 experience came out to about $5/gallon equivalent!
- Infrastructure chaos will exist for a while. So many different services for charging, very little cross-network, lots of accounts and cards needed. Once my driving patterns are more established, it will be easier to have a regular flow.
The Data
The car I got, a Chevy Bolt EV, has an interface with rather limited information about the actual battery, so apologies that some of this report out references “fuzzy” data about the state of battery. As someone used to dealing with kWh or State of Charge measurements, I wish I had access to better metrics. Instead, the interface gives you the estimated miles of range you have. And when charging, it doesn’t tell you the amount of energy you added, just the new estimated range. So…I feel I’m driving blind, so to speak. In any case, here is what I have observed so far.
“Mileage”: 4.2 miles/kwh reported by car
Car Day 0: 4,887 miles on car and battery reports 183 miles of range
Day Day 20: 5175 miles on the car (288 miles driven) and battery full (241 mirange).
Charging Spend: $20.24. ~14 miles/$ spent charging (but not a great way to express since I have added miles to range from when I started…so actually a bit better).
Charging observations:
- Fast chargers have awesome ability to add miles, especially when the battery is less than half full. But…overall could be more expensive than driving an ICE vehicle. In my one experience, I got 5.8 miles for every dollar spent charging. If we compare to an ICE vehicle with 30 MPG, then this would mean I would be paying the equivalent of >$5/gallon of gas!
- Level 2 chargers seem like a great fit for office buildings, apartment buildings or other places where people park fro 4–8+ hours. Haven’t tried out any paid services for Level 2 yet.
- Charging from my home plug was surprisingly economical, when time permits. Even with this, though, the charging speed dropped by half when the battery was nearly full.
Here’s the data I’ve collected so far. One thing I realized in reflecting on this after originally posting the article is that I don’t have a good way to know how much energy is in the battery. The numbers reported below are how much energy is delivered to the car, which I can measure very accurately in some cases (eg at home or with EvGo). But there are clearly some inefficiencies in the conversion to storage in the car battery. I will try to delve into this in future posts. Any other patterns you notice?
