Thoughts on Estimated Range

[Vim Schrotnock]

There have been a lot of discussions on the accuracy of Porsche's 'estimated range' and I'd like to provide a bit of discussion and data on my recent experiences.

I had my battery replaced in August , and have been tracking various parameters using the iCar Pro OBD reader. I've been charging every day to 85%, and have done a 'rebalancing' consisting of letting the car sit overnight with <10% charge, then fully charging (level 2) and letting it sit overnight. Since August, I've only taken two long trips - about 400 mi. round trip each.

My range estimates (all estimated at 100% charge in normal mode) started out around 260 mi. when I got the battery replaced in August, and after driving a month or so around town, I was getting over 300 mi. estimated range. I took a 400 mi. round trip with fast charging to 100% and my range dropped to around 230 after the trip - a significant drop of 70 miles. I checked all the voltages and SOH at high and low voltages, and the cells looked great. I drove around town for a few months, and the range went back up to 260. I took another 400 mi. trip and the range dropped to 220 afterwards. Now, after several months of driving around town, it is back to almost 260 (in freezing temperatures).

The ACTUAL range I was getting on these long trips was around 240 in Range mode. I think the range estimating algorithm uses your most recent driving experience to estimate range. Driving at 70+ mph for 400 miles gives a lower range than driving around town, so the initial range estimates after a long trip reflected the actual range for long distance driving. Driving around town gives a longer range and this is reflected in the range estimate. I was surprised at how much the range changed after only one trip, but perhaps this was because I don’t have a lot of miles on the battery.

Other experiences?

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[gtm]

@Vim Schrotnock - My GOM pretty much matches yours. Original battery/modules and 17,000 miles. I seldom use the car for 5 mile local trips, typically 25+ miles. In flat, warm Florida my range at 100% usually works out to 260 to 270 miles with that kind of driving pattern. Just took a trip North to NJ for Thanksgiving. 2,300 miles round trip through the mountains of SC, NC and VA (so much better than route 95). Between the hills, highway speeds, and unseasonably cold temps my GOM range dropped to 220 miles. It was accurate and the lost range was real. After two weeks and approx 100 miles of driving back in Florida the range has crept up to 250 miles. I'm pretty sure I'll get back to the high 260 range before long. I've seen this pattern several times with my car and this trip but never got as low as 220 miles of range, but this was also the coldest weather. The first time my range dropped I knew it was the battery failing. Like you I checked voltages and did a rebalance. Everything seemed fine. Now I chalk it up to the software being pretty good at extrapolating from recent driving.

 

[CaliPorsche]

This is somewhat reductive … but essentially any car’s estimated GOM range (unless tampered with for nefarious reasons) is a formula based on three basic things:-
1-The amount of energy in the battery,
2-the efficiency of extracting that energy,
3-the efficiency of the deployment of that energy into traction distance.

So for 1 …. a larger better battery gets you farthest, for 2 …….the ambient temperature and battery temperature the BMS and the onboard losses, for 3……. the journey and driver style specifics.

in other words for 3 if you are climbing a hill, driving at 90 mph, hard acceleration there are drastic changes in the GOM.

I am ignoring many other aspects such as recuperation …… but in essence how you have recently driven affects the GOMs suggested distance left in battery.

as I said …., reductive…..

Example. As recently as last week I was driving a 130 mile trip in a 25 RWD loaner. When I left it was showing 65 % and 214 miles. Half way mark it was showing 76 miles left in battery with 62 miles to go. I dropped my speed to 75 and driving more serene, I arrived home with 60 miles left in the GOM.

btw - my arrival time in Waze only eroded by 2 minutes after dropping speed and driving habits ?

 

[Grim]

I would expect this to be totally normal.

The range displayed will be based on the energy consumption over a relatively recent period of driving (presumably using some algorithm which is biased towards more recent energy consumption) as the car will assume that this will be indicative of future consumption.

If you recently drove a lot in town (low speed) then energy usage is likely to be lower than if you drove at 70mph+ on a motorway. So your range estimate is likely to be higher after a lot of town driving than if you drove at speed.

Other things which will affect range estimates will include:
- whether you were recently gaining altitude or descending
- temperature (too low and battery will be less efficient and you will use energy to heat car, too high and you will use energy to lower AC)
- driving mode (sport and sport+ will both heat the battery for better discharge performance to make power available on tap - this heating also uses energy from battery)
- whether you were preconditioning the battery for fast charging on a long drive (using energy for heat not distance/range)
- weather conditions (wind strength and direction vs direction of driving or heavy rain which may increase rolling resistance)

 

[W1NGE]

There have been a lot of discussions on the accuracy of Porsche's 'estimated range' and I'd like to provide a bit of discussion and data on my recent experiences.

I had my battery replaced in August , and have been tracking various parameters using the iCar Pro OBD reader. I've been charging every day to 85%, and have done a 'rebalancing' consisting of letting the car sit overnight with <10% charge, then fully charging (level 2) and letting it sit overnight. Since August, I've only taken two long trips - about 400 mi. round trip each.

My range estimates (all estimated at 100% charge in normal mode) started out around 260 mi. when I got the battery replaced in August, and after driving a month or so around town, I was getting over 300 mi. estimated range. I took a 400 mi. round trip with fast charging to 100% and my range dropped to around 230 after the trip - a significant drop of 70 miles. I checked all the voltages and SOH at high and low voltages, and the cells looked great. I drove around town for a few months, and the range went back up to 260. I took another 400 mi. trip and the range dropped to 220 afterwards. Now, after several months of driving around town, it is back to almost 260 (in freezing temperatures).

The ACTUAL range I was getting on these long trips was around 240 in Range mode. I think the range estimating algorithm uses your most recent driving experience to estimate range. Driving at 70+ mph for 400 miles gives a lower range than driving around town, so the initial range estimates after a long trip reflected the actual range for long distance driving. Driving around town gives a longer range and this is reflected in the range estimate. I was surprised at how much the range changed after only one trip, but perhaps this was because I don’t have a lot of miles on the battery.

Other experiences?

My understanding has always been that the car remembers thr most recent driving actual range say of the last few trips and uses that as the basis of the estimate after a charging session.

Quite different therefore to the fuel gauge on an ICE vehicle which is why I think we get hung up on the range estimate on an EV.

Consumption is a better measure on any given day.

We can get clever and look at many other data points but in the end without knowing the algorithm used for the range estimate it may quickly become a futile and academic exercise.

 

[SergeyIndy]

After my first out of town 1,000 mile trip, I have simple understanding of how much range I have.

Charged to 100% after the road trip as part of the rebalance with car showing 206 miles.
Charged to 100% after usual in town driving as part of the rebalance with car showing 285 miles, then after a few minutes of driving it showed 260 miles.

I know there are more variables like ambient temperatures, but to me, this means that I have 200 miles for 70mph highway trips if I want to go down to a few miles left on arrival. I do not mind stopping and charging if I know that I can have an available working stall at least with 150kW rating. My recent experience showed that charging stations are busier than before with only a few broken compared to 2 years ago with only hope they add more of them over time as more EVs are sold.

I estimate that I can do 250 miles for in town driving, which does not matter to me as I can charge at home or anywhere in the area with no issues.

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