WaterboyNorCal
Well-known member
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- #1
WARNING- long post.
First of all, in no way am I recommending doing what I just did. I know there are plenty of Youtubers out there who have run these trucks below 0% SOC indicated, but there are also other stories of people having their SOC drop precipitously when below 10% indicated. I will also add that I regularly charge my truck above 90% and deplete it below 10% in an attempt to have the BMS SOC estimate be as accurate as possible. (Daily charge to 80 or 85% but charge above 95% probably 10x per year) That being said, today’s experience scared the living bejesus out of me.
So here’s what happened. I was on a road trip from Oregon back down to California, driving from Grants Pass southbound, planning on charging in Ashland (Oregon) at the Tesla supercharger station. I was a few miles south of Grant’s Pass at about 18% SOC, wondering if I should stop to charge in Medford, which is about halfway to Ashland. Assuming that the BMS was well calibrated and the SOC estimate was accurate, I quickly calculated that I had to average just over 2 miles/kWh to make it with a few percent SOC to spare.
However, even though the wise part of my brain was telling me to pull over to charge in Medford, the adventurous part my brain wanted to find out where the true bottom of the pack was. Some more quick math in my head told me that I was on track to make it, so I rolled through Medford without stopping and had about 13 miles to go and 8% SOC indicated. Even with about 800 feet of elevation gain in those 13 miles, I should’ve been able to make it without issue. However, about 6 miles out, I was down to 4% SOC indicated with more climbing to go and no significant shoulder on the highway. Also, it was 99° outside and I had the AC set at 65 to keep the dog happy.
I finally made the first smart decision of the afternoon and exited the highway, worried about the fact that my power percentage was at 50% and I really didn’t want to find myself stranded on the side of Interstate 5 with a crappy, thin shoulder, waiting for a tow truck. The final 5 miles were excruciating, watching the SOC slowly drop and my power meter steadily decrease… About a mile out from the Tesla station, I cut the AC, the fan, and turned the radio off; I was at 1% SOC. The lowest I had gone before today was 4% and that was in my neighborhood, where I knew that in the worst case scenario, I could get some buddies to push it to the closest neighbor’s house and plug into AC power for an hour if necessary, just to get enough juice to limp home.
Turns out there’s a small hill leading up to the Tesla supercharger in Ashland, and that thing looked like Mount Everest now that I was at 0% SOC. As luck would have it, there was a sizable turnout just before the hill, so I pulled over, powered the truck completely off, waited about 15 seconds and then restarted it. As I’ve seen on a variety of YouTube videos and internet posts, this restored the power remaining from 24% back up to 33%, though the SOC remained at 0% indicated. I had no other choice but to go for it and luckily, I rolled into the supercharger station still at 33% power.
Now I know that my BMS in this particular truck (a 2023 XLT SR with 43k miles so far) is fairly well calibrated, though I don’t think going below 5% SOC is for the faint of heart. I will add that a few months ago, the I performed the HV battery calibration procedure that’s outlined on the Mach-e forum by “Mach-Lee”. Although some people think it’s garbage, I don’t believe there’s any reason to think that running an HV pack down below 10% and then AC charging all the way to 100% wouldn’t assist the BMS in more accurately calculating the SOC. Doing so also updated my “HVB SOH” from 96% to 98%.
Good luck to all of you Kramer’s out there (a Seinfeld reference for those who don’t know), and obviously, your mileage may vary.?
First of all, in no way am I recommending doing what I just did. I know there are plenty of Youtubers out there who have run these trucks below 0% SOC indicated, but there are also other stories of people having their SOC drop precipitously when below 10% indicated. I will also add that I regularly charge my truck above 90% and deplete it below 10% in an attempt to have the BMS SOC estimate be as accurate as possible. (Daily charge to 80 or 85% but charge above 95% probably 10x per year) That being said, today’s experience scared the living bejesus out of me.
So here’s what happened. I was on a road trip from Oregon back down to California, driving from Grants Pass southbound, planning on charging in Ashland (Oregon) at the Tesla supercharger station. I was a few miles south of Grant’s Pass at about 18% SOC, wondering if I should stop to charge in Medford, which is about halfway to Ashland. Assuming that the BMS was well calibrated and the SOC estimate was accurate, I quickly calculated that I had to average just over 2 miles/kWh to make it with a few percent SOC to spare.
However, even though the wise part of my brain was telling me to pull over to charge in Medford, the adventurous part my brain wanted to find out where the true bottom of the pack was. Some more quick math in my head told me that I was on track to make it, so I rolled through Medford without stopping and had about 13 miles to go and 8% SOC indicated. Even with about 800 feet of elevation gain in those 13 miles, I should’ve been able to make it without issue. However, about 6 miles out, I was down to 4% SOC indicated with more climbing to go and no significant shoulder on the highway. Also, it was 99° outside and I had the AC set at 65 to keep the dog happy.
I finally made the first smart decision of the afternoon and exited the highway, worried about the fact that my power percentage was at 50% and I really didn’t want to find myself stranded on the side of Interstate 5 with a crappy, thin shoulder, waiting for a tow truck. The final 5 miles were excruciating, watching the SOC slowly drop and my power meter steadily decrease… About a mile out from the Tesla station, I cut the AC, the fan, and turned the radio off; I was at 1% SOC. The lowest I had gone before today was 4% and that was in my neighborhood, where I knew that in the worst case scenario, I could get some buddies to push it to the closest neighbor’s house and plug into AC power for an hour if necessary, just to get enough juice to limp home.
Turns out there’s a small hill leading up to the Tesla supercharger in Ashland, and that thing looked like Mount Everest now that I was at 0% SOC. As luck would have it, there was a sizable turnout just before the hill, so I pulled over, powered the truck completely off, waited about 15 seconds and then restarted it. As I’ve seen on a variety of YouTube videos and internet posts, this restored the power remaining from 24% back up to 33%, though the SOC remained at 0% indicated. I had no other choice but to go for it and luckily, I rolled into the supercharger station still at 33% power.
Now I know that my BMS in this particular truck (a 2023 XLT SR with 43k miles so far) is fairly well calibrated, though I don’t think going below 5% SOC is for the faint of heart. I will add that a few months ago, the I performed the HV battery calibration procedure that’s outlined on the Mach-e forum by “Mach-Lee”. Although some people think it’s garbage, I don’t believe there’s any reason to think that running an HV pack down below 10% and then AC charging all the way to 100% wouldn’t assist the BMS in more accurately calculating the SOC. Doing so also updated my “HVB SOH” from 96% to 98%.
Good luck to all of you Kramer’s out there (a Seinfeld reference for those who don’t know), and obviously, your mileage may vary.?
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