Wesley's Tool-Box

GM Korea has issued a final recall for 2017-2019 Bolt EVs on June 4, 2021 which updates the battery management software to better monitor and warn against rare battery fires. I had the update applied on the first day, then drove the car around to sufficiently drain the battery. After returning, I plugged the car into a local DCFC station that I previously used for getting the detailed charging curves just over two years ago. These are the results of the new measurements.

The curved had changed significantly after the update. If you compare it with the previous data, you'll notice that the curve is no longer stepped. It's showing a gradual decline starting from about 42% SoC instead. This is close to the sort of curve that was originally seen on the 2020 and later model years of Bolt. The overall time to charge didn't change much, though.

There have been some wild changes in outside temperature during the past week. On Wednesday, February 17, it dropped to as low as about -10C (14F) and stayed consistently low. In contrast, it went up as high as 21C (70F) on Sunday, February 21. It just so happened that I needed to drive my Bolt EV from Naju to Seoul and back on those days. I did anticipate a big difference in drivable range between them, but it was still a bit jarring to experience it firsthand in such a short period.

The trips were made mostly on the same corridor of Honam / Cheonan-Nonsan / Gyeongbu expressways, which took up about 80% of the total distance and where I drove at a speed of 100 km/h (62 mph) on the dashboard. On other roads, the speed limits were always observed. I did not use any heating or air conditioning at all, as evidenced by the pie chart on the screen showing that all the energy was spent for driving.

A Naju-Seoul trip, which is roughly 320 km (200 miles) one way, can be made without a pit stop if the temperatures are above freezing. On Wednesday, I saw the drivable range drop considerably shortly after starting out. Although the battery was initially nearly full, I needed to stop and recharge mid-way, just enough so that I wouldn't be late for the schedule. The temperatures stayed between -8C and -5C (18F and 23F).

The return trip was the same - I filled up the car before starting, but had to recharge at the last service area to give myself a bit of safety margin. In the end 114.3 kWh was spent during the total trip distance of 705.5 km (438.4 miles), resulting in an efficiency of 6.17 km/kWh (3.84 mi/kWh). Given that I only try to spend a maximum of about 50 kWh on a single charge, you can see why I had to do the pit stops.

The situation on Sunday was completely different. It was exceptionally warm for Winter and I could foresee that I would reach Seoul quite comfortably on a single charge. Indeed, the temperature stayed around 20C (68F) for most of the trip until the Sun set. The dashboard showed about 100 km (62 miles) of range left when I reached the hotel.

The next day wasn't much different, although slightly cooler. I was returning to Naju with a full charge while the outside temperature was mostly in the 15C to 20C range (59F to 68F). Total distance of 706.5 km (439.0 miles) was covered using just 85.1 kWh, which gives an efficiency of 8.30 km/kWh (5.16 mi/kWh).

To put this into perspective, the efficiency was reduced by 25.7% just because the temperatures dropped by 23C (42F) and all other things remained more or less the same. Had I used heating, things would have been worse. This highlights how sensitive the electric vehicles are to outside conditions.

To keep a detailed log of the Bolt EV's battery status, I've been using a Bluetooth OBD-II adapter that connects to a smartphone for the past two years. While it worked well, I wanted to have a permanent display showing the data and installing an iPhone to do so seemed to be an overkill. So I searched for dedicated "gauge" units that allowed for customization and narrowed the selection down to ScanGauge 2 and UltraGauge MX. The former allowed for more custom data (25 PIDs vs. 8), while the latter had a bigger screen (8 lines vs. 2). I ended up with the bigger screen.

With the device at hand, I had to find a way to program it to display Bolt EV-specific data using the existing custom PID information, and then install it on a place where it is both easily visible and properly shaded. After a bit of work, I was able to fulfill all of the objectives, as you can see in the photo above. The first page shows the actual vehicle speed, accelerator pedal position, various battery information including State of Charge (both raw and displayed), usable capacity, and temperature, as well as current trip distance and 12V battery voltage. Let's see how this was done.

Initially, UltraGauge detects how many of the 60 standard OBD-II PIDs (Parameter Identifications) and 28 self-calculated data it supports are available on the car. Because Bolt EV does not have an internal combustion engine, most of these are irrelevant and unsurprisingly unsupported. Of the 20 said to be usable as shown here, only 7 of them are standard PIDs and none are related to monitoring the high-voltage propulsion battery.
So I had to devote all of the eight custom PID slots available for this purpose. The problem is that the screen for configuring them (MENU - Gauge/Page Menu - Select Gauge/Page - M Gauge Setup) looks like this:

And it's not easy to make sense of it at first. I needed to translate the information found in an unofficial list of custom PIDs for Bolt EV into this format. After reading the UltraGauge MX programming supplement and researching the CAN Bus protocol, I was able to do just that. For these PIDs...
I programmed UltraGauge like this:
You can see that TData is composed of the header and the PID. The header specifies which ECM the data should be coming from and there are at least eight of them (E0 to E7) on Bolt. The numbers used in the formula are entered in hexadecimal, as with other inputs. After making sure that the programmed PIDs were working as intended, I went ahead with the permanent installation of the device.

I usually use somewhere between 5 to 7GB of cellular (mobile) data per month on my iPhone because my data plan gives me 6GB and I make sure not to go over too much. But since last December, I started to notice an unintended, excessive data consumption which caused my monthly usage to hover around 9 to 12GB until April. It then subsided for a while, but it came back last month. I didn't want to pay the carrier more than what I actually used, so I decided do something about it.

The root of this problem has been pinpointed to "Documents & Sync" activity under "System Services" category from fairly early on. You can see that it consumed 6.6GB of data by itself last month, out of 11.51GB total. The difficult part was determining what exact services were causing it, since there were many iOS features depending on synchronizing data and documents to iCloud. After much trial and errors, I was able to find two of them which caused most, of not all, of the issues.

One was the Photos app using the data connection to update Shared Albums and iCloud Photos. This was a bit strange because I have disabled iCloud Photos and my Shared Albums see barely any activity. Still, it had caused a burst of data consumption from time to time, spending up to nearly 1GB in about 10 minutes in the worst case and making the phone hot in the process. After disabling cellular data option within the Photos entry in the Settings app, these bursts were no more.

The other was the iCloud Drive. When I disabled its cellular data use by using the option buried at the bottom of the Cellular entry in the Settings app, the remaining excess usage stopped. Come to think of it, the data consumed during normal use, be it using the camera, browsing the internet, or interacting with the social media, was roughly twice the previously normal level. So whatever I did, the iCloud Drive was trying to sync some undetermined data in parallel, even though I had no intention of letting it do that. The available space in the Drive did not change, so I would guess it was some sort of system-level stuff.

By the way, the Internet searches I did while trying to fix this problem revealed that a lot of people had similar experiences, but with slightly different solutions. Some people had success by adjusting settings related to iMessages or Keychain, to name a few. So my solution may not be definitive for everyone and you should treat it as a starting point.

I keep a detailed log of my Bolt EV drives to gain insights to the questions I wanted answers to. One of them was this feeling that the drivable range was getting lower on a cold day despite the fact that I drive without having the heater on. Since my EV driving habits became consistent after driving for about half a year, I decided to analyze one full year's of driving from February 2019 to January 2020 to spot a trend between the ambient temperature and the car's efficiency ("fuel economy").

The results above speak for themselves. Even if you don't use a heater, the car's efficiency will certainly drop as the outside air gets colder. This is largely because the air itself becomes more dense, increasing resistance. Using a heater will impact efficiency on top of this. Meanwhile, driving at an average trip speed of about 50 km/h (30 mph) yielded about 1 to 1.5 km/kWh better efficiency than at about 80 km/h (50 mph). Again, less air drag meant better outcome.

If you want to know how the data points were chosen, please read on.

My two most common driving patterns happen on expressways and intercity roads. The former are usually for the long distance family trips. The latter are used in the routine errands between Naju and Gwangju for groceries or movie-going. Downtown driving is done mostly by my wife and there are no records of time or temperature, so they were not analyzed.

As all trips start and end within cities, the most significant and fastest road type used must take up at least 75% of the entire distance for a sample to be representative of a type. And to minimize impacts of traffic jams, average speed of a trip had to be at least 70 km/h for expressway and 40 km/h for intercity. Driving under rain or snow were also out in order to avoid other weather factors. Additionally, expressway trips had to be at least 100 km long and the intercity trips had to have no significant deviations from the most common 22 km-long route I take. Use of heater was completely avoided, while air conditioning was used very sparingly if needed and took up less than 1% of the battery consumption.

In the end, 108 samples spanning a total distance of more than 10,600 km were chosen out of the 27,000 km total distance covered during the period. The real life driving conditions did still create some variability, but the trends were clearly present. I can now use this analysis to better plan for future trips.