Range Estimate

[MarkH]

Talking about a 94kWh 2016 BEV.

Have had it for a couple of years now and it has consistently over-estimated the remaining range.
I never look at this with my normal driving around town, but it suddenly becomes very relevant when on a 100km plus open road trip.

The over-estimate is not caused by the change from town driving to open road driving because the estimated remaining range continues to drop at a lower rate than the actual remaining distance (say, to the next charging station) even after an intermediate charge 100km through the open road trip - so not affected by the immediate past 40kms of driving.

My question is: Is there a way to tweak the algorithm used in this calculation using either BimmerCode or BimmerLink? A "fudge-factor" of say 85% would make the estimate much closer to reality for me (and save the need for mental mathematical gymnastics while driving.)

 

[eNate]

I've never heard of anybody coding a custom "burn rate" but I do have a question: are you plugging your destination into Nav? And is this generally relatively flat terrain?

 

[MarkH]

Yes: open road running usually using navigation.
Usually not flat terrain, but I thought the algorithm should figure that out.

 

[eNate]

Nav is supposed to figure in elevation. I was asking more as a follow up if you weren't using nav. That's got me curious.

What I'm most surprised about is the range should be self-adjusting in relation to battery degradation, if that's causing the problem.

Anyhow, sorry I don't have any advice but please post an update if you figure something out.

 

[3pete]

How far off are we talking here? 1%, 10% 25%?

Anecdotally, I have found that the range estimate is not linear. I definitely think BMW sandbagged a bit in the algorithm to minimize the amount of i3 drivers stranded by the side of the road. I feel like this means 100-50% charge is the car's "best guess" at accurately estimating range (granted, this will have some +/- error in it), somewhere around 25% miles is where the car is saying, "Hey, you need get to a charge, don't risk it!" with increasing panic down to around 5% where it seems like the last 5% is equivalent to the previous 10%.

To your specific question: no- I've never heard of a way to adjust the Guess-O-Meter logic.

 

[MarkH]

Thanks 3pete
My feeling is (but not measured) that it overestimates the range, at the start of a trip, by around 20%.

Here in New Zealand there is not a dense population of charging stations, so, if you just start to look for one at 25%, then you are already up the creek without a paddle. It is quite common for the next charger to be more than 75kms away.

Hence my desire to have a better handle on the actual range left in the battery.

Seems, from what you say, that I'll just have to improve the sophistication of my mental gymnastics.
Might have to start logging things to understand the regressions better!

 

[JohnKelly]

I find that while using the navigation you get pretty good range estimation and it tends to fudge on the side of caution, and gets more accurate the closer you are to your destination. Doesn't a 2016 i3 have a 60ah battery, by the way?

 

[MarkH]

Mine errs on the side of optimism. I'd prefer the other way: but, yes, it does get more accurate as the battery gets further down.
My i3 is ex UK and is definitely 2016 and 94ah.
WBY1Z62070V719113

 

[MarkH]

Here's some figures - first time out of town for a while.

76 km from home (by GPS) i3 says 142 km range left - so I have 66 km buffer.
When I get home the range left is 29kms (not 66, or anything like it).

So, in driving an actual 76 km I have used up 113 km of the apparent range the car estimated.
I am getting only 76% of the apparent range.

Is this what others are finding? or is my car's estimation worse than what others are finding?
BTW all but 5km was open road running, typically at 95kph.

 

[eNate]

Mark, is your car connected? I'm wondering if there's a difference between in-car nav versus a BMW server mapping elevation profiles.

Also, how warm was it outside?

 

[3pete]

I'd also ask: are you navigating your route home using the car's navigation system? If you do use the i3's navigation it will/should adjust the range estimate for your specific route but if not it's just basing it on recent consumption.

When I get home the range left is 29kms (not 66, or anything like it).

If you're up for it, I'd suggest taking your car back out at this point and seeing how long those 29kms last. I'd bet it's longer than 29kms, but of course make sure you do this on a route where you have charge options if it keeps dropping at an accelerated rate. Circling your house may not be fun but at least that way you know you won't run out of juice.