Over the past few weeks I collected some more data at home here in SLC, UT, and I wanted to share it here. I also notified Lucid a few weeks ago with no real response as of yet. I apologize for the length of this post, but I want to include as much detail and context as I can. Let's get into it!
My goal with each of these tests was to determine how high ambient temperatures and a warm battery affect fast charging speeds with my car. The cases in which I've seen these poor charging speeds circumstantially were after several hours of driving in temperatures of 95F+ and after 2-3 fast charging sessions, and I wanted to see if I could replicate these scenarios reliably. For each of these tests my car was left outside in the sun from about 7am to 3pm, with interior temperatures reaching 120-130F before getting into the car. I would then spend at least 30 minutes preconditioning the battery for fast charging as well as driving the car up the nearby canyon in Sprint mode in attempt to add heat to the battery/drivetrain, followed by descending the canyon in Smooth mode while utilizing as much regen as possible. Distance travelled from the parking space, to the top of the canyon, and back down to the charger was between 15-25 miles with about 1000 feet of elevation gain and then loss. For the first test the battery was preconditioned for about 30 minutes, with the last two being a minimum of 45 minutes. Ambient temperatures for each were around 98F, +/- a few degrees.
Test #1 - July 24th, 2024 - Electify America in Millcreek, UT
After following the pre-testing procedure above, I arrived at the station with 6% SoC and the car reading an ambient temperature of 102F. Charing speeds peaked at 78 kW. After about 5 minutes of charging with no improvements in speeds seen, I tried 2 of the other 3 chargers at the site to verify it wasn't a charger-specific issue. At this point I decided to unplug the car to let it sit and precondition for an additional 20 minutes before charging again. After doing this I reached a peak charging speed of 175 kW at 14% SoC. Speeds held relatively steady until 45% SoC, when speeds began to drop sharply, eventually going below 10 kW at 50% SoC. This continued for 10 minutes before finally ticking over to 51% from 50%. At this point I swapped chargers again just in case the charging cable/handle was overheating and limiting speeds. Speeds peaked at 15-20 kW. Over the next few minutes speeds did slightly recover, reaching up to around 80 kW, before dropping again to 25 kW at 67% SoC. Charging time from 6-50% was a little over 30 minutes, and another 30 minutes to go from 50% SoC to 67% SoC. During this test I was the only one charging, save for the last 15 minutes or so when an Ioniq 5 plugged into the opposite pair of chargers and was getting 240 kW at 40% SoC.
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Test #2 - August 2nd, 2024 - EVgo in West Valley City, UT
I followed the same pre-testing routine as before, this time adding 30 minutes of preconditioning time via the mobile app before getting into the car. I arrived at the station with 6% SoC and the car reading an ambient temperature of 103F. Initial speed was around 35 kW. After a couple of minutes I swapped to the other functional 350 kW unit and peaked around 45 kW at 10% SoC. After 15 minutes of charging I only reached 21% SoC. At this point I unplugged the car and let it sit and precondition for 30 minutes before resuming charging to see if speeds would improve. With this new session speeds peaked at 58 kW at 17% SoC. I remained on this charger for the next 30 minutes, as speeds steadily decreased to 20kW at 36% SoC. An Etron and MachE both came and went during this time, each charging at speeds of at least 100 kW. In total I spent a little over 45 minutes to go from 6% to 36% SoC, after losing 4% in between sessions from preconditioning and air conditioning.
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Test #3 - August 3rd 2024 - Electrify America in Millcreek, UT
Unfortunately it wasn't until after the second test that I realized that the unofficial API displays the battery's maximum and minimum cell temperatures, so I decided to run one more test to try and observe how these temperatures changed over time. After following the usual pre-testing procedures I arrived at the charger with 1% SoC and the car reading an ambient temperature of 97F. I noted that before remotely preconditioning max/min cell temps were 45.3C/40.2C, down to 38.4C/37.1C after 40 minutes of preconditioning, up to 46.3C/44.6C after reaching the top of the canyon, and finally 48.4C/46.2C after arriving at the charger. At this point charging speeds peaked at around 90 kW upon reaching 5% SoC. After about 15-20 minutes of charging and reaching 20% SoC I swapped to another unit to rule out charger-specific issues. Speeds steadily decreased to around 40 kW by 40% SoC with cell temps of 52.4C/49.3C. At this point I tried the two remaining units with no improvements in charging speeds seen. At this point an Ioniq 6 pulled in and plugged into the unit I had initially been using and began charging at 230 kW at 16% SoC. By 60% SoC cell temps were up to 54.1C/50.6C. At this point cell temps began to gradually decrease instead of increase, and I noted that Ioniq 6 had already passed my SoC in under 10 minutes of charging. It took about 70-75 minutes for me to charge from 1% to 65% SoC.
Test #4 - August 8th 2024 - EVgo in West Valley City, UT followed by Electrify America in Millcreek, UT
While I feel fairly confident that I did not encounter any charger or site-specific issues while charging in the previous tests, I still wanted to demonstrate that my car would still charge normally when not overheated at these stations. I woke up early, pulled my car out of the garage, and let it sit and precondition for 45 minutes with ambient temperatures around 72F. I arrived at the EVgo station with 11% SoC and charging speeds peaked around 175 kW. Still not ideal speeds, but it appears this site may still have an amperage limitation that I noted many months ago, so I suspect the charger was at least partially limiting speeds here. At this point I unplugged and made the 10 minute journey to the Electrify America station. I arrived at 9% SoC and very briefly peaked at slightly over 200 kW. The car seemed to follow it's normal charging curve, albeit lower about 20-50 kW. It took 20 minutes of charging to go from 9% to 50% SoC.
If you've made it this far. thank you very much for reading!
Let me be the first to say that I am not an automotive or electrical engineer, so my understanding of all these things is basic, at best. However, the fast charging behavior I've been seeing over the past month and a half does not seem normal, at least when comparing to the same time period last year. I really don't know if this is due to some undiscovered thermal management issue, or if this is new behavior as the result of software updates over the past year, or if this has just been normal behavior all along. From my perspective, it seems abnormal and concerning. As far as I'm aware, there aren't any other modern EVs that have this poor of charging behavior in hot weather, but perhaps I'm just not fully informed. If this is really normal, I also wonder why owners in places like Phoenix or Las Vegas aren't more vocal about this or encounter this frequently, but perhaps I'm just overthinking it all. In any case, I'd really appreciate feedback and thoughts from fellow owners here whether you think this is all normal or not. Thanks again for reading and all the best!
