Over the holidays, I’ll be driving my BMW iX for a 1,100-mile trip in two days, charging at EA L3 sites along the way. I’ve heard that the BMW battery management system can slow down the charging after a while. Has anyone experienced this or have any details to share? I’m curious if it’s based on the number of charges or the total kWh gained, and what the charging rate might look like if it enters a ‘protect’ mode. Also, will an overnight hotel rest reset the system? (I could try a Level 2 charge overnight, but it would be inconvenient).
If you charge multiple times in a short period, you’ll likely experience a limit on charging power. This usually resets after an AC charge or after a couple of days.
Ellery said:
If you charge multiple times in a short period, you’ll likely experience a limit on charging power. This usually resets after an AC charge or after a couple of days.
Yes, it can get pretty bad. On one trip, I did three DC charges in a row, and on the fourth, I was only getting 5 kW. There was no warning, but it was clearly throttled. After one AC charge (11 kW), I was back to normal speeds. I learned my lesson and won’t charge to 100% on trips again.
@Vesper
Thanks for sharing that, although it’s not an ideal situation. I’m planning to avoid charging to 100% except for the initial charge, so hopefully, that helps. 5 kW on a L3 charger sounds like a nightmare, especially when you’re on a schedule.
@Adair
That should definitely help! I’ve done long trips before, charging to 80%, and didn’t notice any major delays despite the system telling me it was throttled. I’ll follow the car’s charging recommendations on my next trip. The car should know best.
I’ve heard about this too. A while ago, Out of Spec drove an i7 cross-country and they were worried about it, though I’m not sure if it actually happened. The i7 is different from the iX, so it might behave differently. If it happens, it doesn’t seem too bad. Some slowdowns were noticed, but nothing major that would ruin the trip. Also, the rumor is that charging on Level 2 at a hotel will reset the system.
@Taylor
They both have the same battery and protections.
Ellery said:
@Taylor
They both have the same battery and protections.
I’m not sure the battery management system is exactly the same between the i7 and iX. One is a repurposed model, the other a ground-up EV.
@Taylor
The battery units are shaped differently, but the internal architecture is similar. They’re both Gen 5 batteries and essentially the same. I work on these cars, so I know the details.
@Taylor
Thanks for the info. If the slowdowns are just to 130 kW, that’s manageable. I remember seeing a report with slower speeds, down to 50 kW, which would definitely affect the schedule. I’ll probably need to find a hotel with a Level 2 charger and hope the spots aren’t taken when I arrive late.
To cover this distance, you’ll likely need two or three DCFC charges per day, so battery protection shouldn’t be a concern. It’s more of an issue if you do four or more DCFC sessions in a short period. The system will reset with a quick AC charge, but that’s probably not something you’ll need to do.
The battery protection doesn’t actually limit the top charging speed; it just makes the charging curve steeper, slowing down more quickly. At worst, you might lose 5-10 minutes of charging time from 10-80%. You’ll be fine, though. I’ve done trips with 18 HPC charges in two days, and the power still reached 195 kW on the last session. There are many factors affecting speed, like the battery temperature or charger limits, so the effect of the protection mechanism is barely noticeable if you’re not paying attention.
@Vesper
That’s exactly what I’m hoping for! The good news is my hotel has a Tesla destination charger, so I can do an AC charge in the middle of the trip with my adapter.
I think the charging curve just slows down as the battery fills up. You’ll be fine if you keep the charge below 80% and move on to the next charging station.
Good luck on the trip! Be prepared for possible delays with the charging stations.