Wesley's Tool-Box

Korea's Ministry of Environment (ME) has been aggressively expanding its network of DC Fast Charging (DCFC) stations throughout the country, with more than 1,100 new chargers being installed and operating in pilot mode since early this year, accounting for nearly 40% of total. I was fortunate enough to live close to one of such stations (and a 100kW version at that), which let me test out the charging characteristics of my Bolt EV without costing me a dime.

Although the chargers are supposed to switch to normal paid operation starting mid-May as the firmware updates are deployed in a staggered manner, I was able to observe what the close-to-ideal charging situation would be before this happened to the nearby charger. The following graphs plot the data I recorded.

It should be noted that the ME chargers have either a 40-minute or a 41-minute time-out. This was done to prevent a single person from hogging the charger for too long. Therefore, I did these charging sessions during the early hours in the morning when no one else was around in order to have as close to continuous charging as possible. This led to a bit of "blips" in the graph (64% - 41st minute / 88% - 82nd minute), but it did not affect the overall picture that much.


Charging speed is largely dependent on the battery's State of Charge (SoC), so it helps to see the data as its function. As you can see, the charging current remains more or less constant at a given "zone", then drops down a step after a certain level of SoC is reached.

The actual charging power will slowly increase in a zone because the charging voltage rises. This is a direct reflection of the the voltage of the battery cells themselves, which rise as the energy is filled up. The 288 cells are arranged as 96 groups in series of 3 cells in parallel, so there would be nearly a 100-fold difference between the cell voltage and the charging voltage.

Another major factor in the speed is the battery's temperature. Assessing multiple charging sessions, it became apparent that it should be around 24 to 27°C at the beginning in order for the Bolt EV to enter maximum current (roughly 150A before 50%). If it's colder, it will start out a bit slower, then ramp up to 150A as the battery heats up to about 24°C. If it's too hot (more than 30°C), the charging current caps to 95A to prevent overheating.


For someone who's waiting for the car to fill up, the time it takes for each of those charging zones is also quite important. So this is a graph showing the same data, but plotted as a function of time. Key numbers are distilled into the following table.

To make a quick comment about the displayed and actual SoC, the two meet at around 75% mark, with the displayed getting larger above and the actual getting larger below. At the extremes the two differ by about 4%, showing the buffer for preventing over-charging or over-discharging.

The power and current values are as seen from the charger. The values from the vehicle's subsystem were about 96% of these, showing the losses inherent in the charging process. Further losses occur as the energy ends up inside the battery, so we end up with a bit more than 10% loss in total.

The advantage of using a 100kW (500V x 200A) charger is apparent only for the first 50% of charge, and is not a huge one at that. 50kW chargers in Korea supply either 110A or 120A maximum current, so the charging speed of 1.06%/minute should extend to below 50% SoC when you use them. Hence, you'll shave about 10 minutes off the session with a 100kW charger instead of a 50kW one if you're starting from 10% charge left. You can thank Bolt EV's highly conservative charging regime for this.

So what's the takeaway from all these information? Probably a good basis for forming a charging strategy during a long-distance trip. To minimize charging times, you should keep the car's SoC between 10 to 20% minimum and 70% to 80% maximum, with each charging session lasting about an hour at most. The last 25% alone takes an hour to charge, so a full charge is not a good strategy unless you're going to a place where the chargers are sparse. Meanwhile, the ambient temperature during charging should be as close to 20°C as possible. Hopefully, you can find a charger within a building or under a shade.

Apple has included 3rd party navigation application support for CarPlay with iOS 12, which means the cars equipped with CarPlay can use maps other than Apple Maps as long as they make use of the new API. Google Maps and Waze were named when the feature was announced back in June, but one of the major Internet Service companies in Korea, Kakao, beat them to the punch and launched the CarPlay-supported version (3.26.0) of its Kakao Navi app today, September 15. As the iOS 12 GM was already released to the developers and beta testers two days ago, it was possible for me to try it out on my Bolt EV as you can see above.


Kakao Navi is no stranger to the car navigation game, as it was selected as the sole navigation app when Google's Android Auto was launched in Korea in July 12 of this year. This happened because the stand-off between Google and the Korean government resulted in a severely crippled Google Maps support in Korea. In any case, Kakao Navi has claimed first 3rd party navigation support on both Google and Apple's car interfaces for Korean users.

After arriving in Ulsan and charging the Bolt EV's battery as seen in the last post, my four-member family went about our own business for a couple of days. When it was time to return home, we dropped by a nearby Costco to pack up some items in the trunk. While the space was smaller compared to the one in the cars I used to drive, we were able to fit everything in.

We spent 18% of the battery charge during our stay, leaving 76%. It seemed a bit risky to attempt a full return without a mid-trip recharge since the previous trip used 73% of the battery. Still, I thought it presented an interesting opportunity to see the car's limits and pressed on casually, with the air conditioning on. The following time-lapse video shows what happened in its entirety.


As you can see, the Bolt EV was able to return to the charging station in the parking lot at home just barely. Like the previous trip, this sort of drain-to-the-bottom run should be attempted only if you're sure of the range and the charger is ready at the end. So what was the scariest moment?

It’s been more than a month since I started driving Bolt EV. The lack of any engine noise, as well as the responsive acceleration and regenerative breaking continue to impress even now. I felt that the car definitely belonged to the 21st century and was glad that this was the first car I bought. Driving experience aside, many still wonder and ask if the car is truly good enough for a long drive and whether the charging speed was any good. This is where showing the experience would be better than explaining.

Here is the video of my recent cross-country round trip with Bolt EV in time lapse mode using the setup you see in the photo above. It should be noted that the Korean Peninsula is only about 300km wide and the South Korean part is about 400km long. Therefore the “cross-country” isn’t on a such grand scale here. Still, the range of Bolt EV (383km) implies that it could go almost anywhere in the country with a single full charge and this is important for many potential buyers in Korea.


On the video, Bolt EV took on the task of taking my family on a routine trip to my parents’ home at the opposite coast. This trip from Naju to Ulsan covered a distance of 302.8km, of which more than three quarters were on the expressway. The day was warm and humid (more than 25C on average, with a bit of rain) and so the air conditioning was running, yet the car nevertheless passed with flying colours with plenty of margins to spare. We started out with 91% charge, and still had 18% left after reaching the destination. Let's see this in more detail.

Indoor uses of thermographic imaging camera include finding leaks of heat or water, owing to the fact that people doing repairs may have the budget and the repeated usage that justify owning such a device. But as the cost to buy one goes down and the size becomes small enough to carry in a pocket, more uses come up. The one I found useful in raising kids is cooking and food safety. As you can see here, a bowl of spaghetti straight out of an oven didn't look particularly dangerous at first...


But with FLIR ONE Pro, you could see that the handle was quite hot. The spaghetti itself was also sizzling at over 70C. This image served as a good way to teach my kids why they should be careful with a bowl that came out of an oven.