[jzhng148]

I think all of you already know that level 2 charges more efficient than level 1 charger. I guess I'm just bored so wanted to find out exact efficiency ratio by compare battery used vs exact electricity pulled from the grid.

Level 1 Charging: use a 120v electricity monitor to monitor KWH consumed by BMW OUC. Assuming the usable battery in U.S. is 17 KWH and calculate remaining battery based on the percentage shown in BMW Connected app.

Level 2 Charging: use a 240v 32A level 2 charger with NEMA 14-50 plug (from Amazon). Same assumption here and I wired an additional meter to the NEMA 14-50 outlet for comparison (it does show more energy consumption than what the charger says).

Here're the numbers:


Seems like the level 2 charger I've records less energy compared to the meter. I plug it to my friend's model 3 today, and the charger showed 10V less than what Tesla indicated but the amp went up to 35A (it's rated as 32A charger) while it should be capped to 32A by Tesla. So I would trust the numbers got from the meter in the table above.

Conclusion: On average, level 2 charger is about 11% more efficient than level 1 charger. And both chargers drop quite a bit in term of efficiency when charge small amount of energy to full battery.

Recommendation: Try to charge the vehicle when the battery is as empty as possible. Upgrade to level 2 charger to save your energy bill if that's an option for you. But I think the biggest gain from switching to level 2 charger is significantly less charging time. You can basically fully charge the battery on 45e for a little over 5 hours, which makes 45e more practical if you plan to use it as an EV.

Happy Thanksgiving everyone...

[jc.bmw]

Thanks for posting! It's interesting to see data on charging times and efficiency!

I've noticed that the last 20% of charging (80 -> 100%) is much much slower on 120v/10A and incredibly slow when doing 120v/6A (because of the iDrive bug).

[taybo20]

Awesome! Thank you!

[jzhng148]

Originally Posted by jc.bmw

Thanks for posting! It's interesting to see data on charging times and efficiency!

I've noticed that the last 20% of charging (80 -> 100%) is much much slower on 120v/10A and incredibly slow when doing 120v/6A (because of the iDrive bug).

Yea, I noticed the car switched to 6A from time to time on 120v outlet, but haven't experienced the same bug on the level 2 charger.

Hopefully BMW will fix the issue in the upcoming software update.

[jzhng148]

Originally Posted by taybo20

Awesome! Thank you!

[jad03060]

NOrmally, a L2 device is on a dedicated circuit, so there'd be no good reason to limit the charging rate, at least in the USA. A L1 device could easily need to share with other things you might plug into that circuit (garage door opener, lights, tools, etc.).