REx 60Ah vs 94Ah vs 120Ah on steep grade

[BL5]

Experienced my first mountain pass on REx the other day with my 60Ah 2015.

I knew this would happen, but once battery hit 1.0% my i3’s max speed was 45-50mph. I forgot to hit HSOC earlier in the trip. No big deal, it was fine and I really wanted to know how it would cope with grade.

Question- My understanding is model years 2017-2018 has a more powerful REx. Does the 2017-2020 REx models still have this same level of power loss when battery hits 1.0% while going up a steep grade? Are the new models able to maintain a normal speed?

Next time I’ll hit HSOC at 40% to make sure there’s no power loss.

 

[SSi3]

The 94 and 120 have the same power cut at 1% but their 6% buffer is bigger than the 60 so less chance of using more power than the REx can provide. And yes they tinkered with the REx tuning for 2017 and bumped the hp up a little to help with this issue as well.

But yes, HSOC solves the problem completely

 

[jadnashuanh]

The original (34Hp) and the 'larger' one (38Hp?) is still the only real power source when you let the battery get down...when was the last time you drove a 34-38Hp vehicle up a long grade? Maybe never, and if you did (at least in the USA), it was probably a really old VW bug...those couldn't get out of their own way well, and their engine was the ONLY propulsion (unless you considered gravity!). Any other vehicle that came with less, you'd have to go back a bunch of years, and most of those people are not driving anymore, if they're still alive!

Marketing forced the addition of the REx. I think without it, they could have put a larger battery in the vehicle.

Today, with the higher energy density of the batteries, the REx has less rationale, at least if you believe BMW's design goal as city car. For the additional $3500 or so for theREx, you could rent a car, or borrow one for those times when you needed to go further and not have the additional maintenance issues any ICE requires.

Some people have reported that their REx only was used a few times over years of ownership...that should say something about the design. Lots of people do not review their needs. When running on the REx, you're paying probably close to at least twice as much for energy to move it along. The advantage is, it's much quicker to refuel than recharge, so you CAN go further if you put up with that restriction. It's a tribute to the car that people can take it on longer trips.

I'll be selling mine for an X5 45e (hybrid) in a couple of weeks, the X5's body was painted today, so shouldn't take that much longer to get to me. Enough EV range for 95% of my needs, but seamless switch to hybrid mode (hearty I-6 engine) to propel me whether I've got battery or gasoline capacity...and, you can have it recharge the batteries itself while on the run, if desired.

 

[BL5]

I’ve found on longer trips, paid DCFC and 92 petro to be a wash per mile. Home charging is a no brainer, my 2015 REx is very cheap to drive per mile.

Best rule of thumb is, code your REx i3 for HSOC, activate HSOC up those steep grades. Otherwise you’ll limp up the hill at low speed.

Sounds like the 2017-2020 REx won’t perform any better at 1% while going up a steep grade. Good to know.

 

[Deutsch100]

Both my former 2019 i3S Rex and my current 2020 i3S Rex are strong when driving on Rex. I have gone up steep freeway passes at 75mph with full A/C and noticed no power loss than when not using Rex. You can hear Rex a little, but it is not obtrusive.

99% of the time I do not use, nor need Rex....but it is such a piece of mind thing, and has totally removed all EV range anxiety.

 

[Obioban]

I’ve found on longer trips, paid DCFC and 92 petro to be a wash per mile. Home charging is a no brainer, my 2015 REx is very cheap to drive per mile.

Best rule of thumb is, code your REx i3 for HSOC, activate HSOC up those steep grades. Otherwise you’ll limp up the hill at low speed.

Sounds like the 2017-2020 REx won’t perform any better at 1% while going up a steep grade. Good to know.

I mean, they'll perform a little better. 38 vs 33 hp is only 5hp more, but it's also 15% more power :lol:

I do think it's far less likely to be an issue with the newer cars, as you have a bigger buffer with the bigger battery, and the buffer depletes at a lower rate, because of the 15% more powerful engine. Combined, it should take a pretty long grade to be able to get the car to 1%