Bmw i3 goes to turtle mode when range extender starts to be used

I have spent hundreds of dollars with bmw trying to figure out why my i3 goes to turtle mode when the range extender kicks in when the battery drains .
Bmw has spent money as well.
2015 model.
Curious as to whether anyone else has experienced this issue.
It only occurs when the battery depletes and range extender kicks in.
BMW Could not figure out a solution.
Example. I was driving south on i95 in Florida. Battery was down to where the range extender kicked on and then the car slowed down to about 40 miles per hour.
I pulled over to the side and kept driving at the slow sped then the car sped up after about two miles. It’s a very dangerous situation especially if I had been in the far left lane.
Curious if anyone else has experienced this.
I have discovered a work around but it entails the use of BimmerCode..
thanks for any feedback.

why not do the $35 workaround with Bimmercode then?
My guesstimate is that the Battery Management System on a 7 year old vehicle with batteries that are degraded is that the system does not work the same as when new. So REX actually comes on later than it should because it "thinks" there is enough battery left, but there actually is not. At that point you are running on the REX only (or mostly).

This can occur when the BMS believes that the battery pack's charge level is higher than it actually is. As a result, the REx turns when the actual charge level is near 0% at which point propulsion power is decreased to maximize remaining range so that a driver would be more likely to reach a charging station. When this happens, you should see power bars begin to disappear in the ePower gauge.

A BMW dealer should be able to recalibrate the BMS. There is apparently a service bulletin describing this problem and the solution.

Yes bmw should! It spent days at the dealer and they could not figure it out.

Yes, I already had BimmerCode and now when the battery gets low I use the function to keep the battery charge, it’s working fine. It’s just hard to understand why BMW couldn’t figure it out after literally days in the shop.
Thanks for the replies!

This article discusses this problem and includes BMW Technical Service Bulletin numbers that you could give to your BMW dealer.

Thank you for the info!!