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Pushing range: How far can you really go?

ZeeDoktor

Member
Dec 3, 2019
173
308
Sydney
I went for a long test drive last night and broke the Model S distance record on Teslafi by clocking up 658km / 409mi in just over 9 hours: TeslaFi.com Shared Drive

The purpose of this experiment was to figure out how far I could push the range by going at an "ultra long range cruise speed". This is useful when travelling in Australia, because it's a big country, with few charging stations when away from the populated east and south coast between Brisbane, Sydney, and Melbourne. After this test, I can now confidently say that leaving on a full charge, I can easily break 600km / 373 mi range without getting nervous about it by simply sticking to at or below 80 km/h / 50 mph speeds - when using autopilot that's not even too fatiguing either.

Given most of Australia is relatively flat, elevation changes account for a small amount of range loss only and really only needs to be factored in when going to a handful of places. To make this realistic, I refrained from going dangerously or inconveniently slow and kept my travel speed between 70 - 80 km/h (43 - 50 mph) - but that still required doing the test overnight so as to avoid slowing down too much other traffic in the Sydney area where I live. Highway speed limits where I was driving were between 80 - 110 km/h (50 - 68 mph). I also wanted to retain most electrical consumer essentials such as entertainment, autopilot, lights, and air blowing into the cabin (albeit with the HVAC system off). I recorded battery metrics in the process using a the tesLAX app and some custom scripts I wrote to log the data. I was particularly interested in figuring out how much buffer really is in my battery pack. The battery management system (BMS) reports a percentage that is different from the one display to the user. As power drains from the battery, these percentages differ significantly, with the BMS reporting 5.7% left when the car reports 0%. This translates into an additional 30km / 18mi of available range until the batteries are really flat. And by flat, I mean they're at 2.8-ish V, which is the point where the Li-ion cells can suffer damage when pushed below. I stopped my drive when they reached 3.0V, but as can be seen from BMS% vs Voltage plot, the BMS percentage reported looks to be set to show 0% when the still safe limit of 2.8V has been reached.

The upshot is simple: Tesla are not hiding a huge amount of range in the battery pack, and what matters most is the speed you're doing. No surprises there really, considering air resistance increases with the square of the velocity. But when getting below 20% battery, things are going decidedly non-linear and you do in fact have a fair bit more range in the batteries than the car's computers want you to believe.

BMSperc_vs_BatV.png

BMSperc_vs_RatedRange.png
 

f205v

Member
May 12, 2018
644
745
Tessin, Switzerland
WOW!
The best I have ever done in my Model S 100D (2017) is 510Km, going from 98% down to 2% battery.
But I was going up and down Alpine passes, so it is difficult to say how much I lost due to elevation changes. Average speed was about 70-75km/h
 
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ZeeDoktor

Member
Dec 3, 2019
173
308
Sydney
You do lose some energy in alpine driving conditions. Regen isn't 100%, but comes close. If you look at my drive details, you'll see that the total altitude climb/descent is nearly 6km, so the many small hills did add up, yet cause minimal range impact. You can take your battery to 0%, there is a buffer built in (about 30km in my case - yours might differ).
 

Ostrichsak

Active Member
Sep 6, 2018
3,323
3,275
Colorado, USA
That's all well and good and all but one time I ran out with 13-miles of range still showing on the display. No warnings, nothing. Just going along at 80mph and then... loss of power with a warning to pull over safely out of traffic as we were coating. We were on a curve with little to no shoulder on the side of I70 so there really was no place safe to pull over but I pulled as far out of traffic as I was able to. The kicker is I was 6.5 from the next Supercharger stop. That set our 3-day weekend trip back several hours and it was a PITA standing on the side of an interstate highway for hours waiting for a tow truck. Ever since then, I'm not about risking it and I don't try to ring every last mile of range. It's just not worth it IMO.
 

SilverGS

Active Member
Nov 3, 2016
1,462
752
Ontario
That's all well and good and all but one time I ran out with 13-miles of range still showing on the display. No warnings, nothing. Just going along at 80mph and then... loss of power with a warning to pull over safely out of traffic as we were coating. We were on a curve with little to no shoulder on the side of I70 so there really was no place safe to pull over but I pulled as far out of traffic as I was able to. The kicker is I was 6.5 from the next Supercharger stop. That set our 3-day weekend trip back several hours and it was a PITA standing on the side of an interstate highway for hours waiting for a tow truck. Ever since then, I'm not about risking it and I don't try to ring every last mile of range. It's just not worth it IMO.
Your tolerance for risk is much higher than mine. :)

I lost my range anxiety after taking one trip the day after I got my car (it was only a 2 hour trip one way, but I miscalculated how far I could go on my charge). Ever since then I always make sure I have at least 15 - 20% charge as buffer left for the next charging stop so that I never have to go through what you had to experience above. I wonder if this behaviour is considered "range anxiety"? :)

Ofcourse this will not apply in places where there isn't a charger available to keep that buffer.
 

Ostrichsak

Active Member
Sep 6, 2018
3,323
3,275
Colorado, USA
Your tolerance for risk is much higher than mine. :)

I lost my range anxiety after taking one trip the day after I got my car (it was only a 2 hour trip one way, but I miscalculated how far I could go on my charge). Ever since then I always make sure I have at least 15 - 20% charge as buffer left for the next charging stop so that I never have to go through what you had to experience above. I wonder if this behaviour is considered "range anxiety"? :)

Ofcourse this will not apply in places where there isn't a charger available to keep that buffer.
Not anymore. lol

I had what I consider to be "range anxiety" when we bought our first EV/Tesla but this was slowly eroded by reading posts on forums from owners about some "mystery reserve" BS and other anecdotal experiences that made me feel like if we did get down that low it wouldn't be a big deal. I helped me to relax a little bit more about that zero number even though I was previously the type who also wouldn't go to 15-20% predicted much like yourself. It's not always that easy depending on what model Tesla you're driving, the conditions and spacing of the Superchargers though. I forced me to take a slightly "riskier" chance than I otherwise would have.

Interesting though that from the moment we left one Supercharger headed for the next my estimated range was always right about 2x what the distance was needed for the next Supercharger stop. This would lead the average human to think you had plenty when you left and question or second guess it once the entire way. The car agreed with me and never once did it warn me to decrease my speed to reach my destination. Nothing at all. Just... dead. First time I've ever run out of "go forward juice" in any vehicle in several decades of driving. Lots of people with cameras taking pictures of the Tesla on the side of the highway as they went by isn't a good look for the brand either as I'm sure whatever they tell their friends won't be good and will further perpetuate the false narratives of the "Tesla experience" as a whole.
 

SilverGS

Active Member
Nov 3, 2016
1,462
752
Ontario
Interesting though that from the moment we left one Supercharger headed for the next my estimated range was always right about 2x what the distance was needed for the next Supercharger stop. This would lead the average human to think you had plenty when you left and question or second guess it once the entire way. The car agreed with me and never once did it warn me to decrease my speed to reach my destination. Nothing at all. Just... dead. First time I've ever run out of "go forward juice" in any vehicle in several decades of driving. Lots of people with cameras taking pictures of the Tesla on the side of the highway as they went by isn't a good look for the brand either as I'm sure whatever they tell their friends won't be good and will further perpetuate the false narratives of the "Tesla experience" as a whole.
Did you ever experience this again - the erroneous charge remaining issue? Scary especially getting stuck on the side of a highway like you did.
 

2101Guy

Active Member
Jan 6, 2020
1,427
1,232
USA
That's all well and good and all but one time I ran out with 13-miles of range still showing on the display. No warnings, nothing. Just going along at 80mph and then... loss of power with a warning to pull over safely out of traffic as we were coating. We were on a curve with little to no shoulder on the side of I70 so there really was no place safe to pull over but I pulled as far out of traffic as I was able to. The kicker is I was 6.5 from the next Supercharger stop. That set our 3-day weekend trip back several hours and it was a PITA standing on the side of an interstate highway for hours waiting for a tow truck. Ever since then, I'm not about risking it and I don't try to ring every last mile of range. It's just not worth it IMO.

you mentioned doing 80mph. When I've been on NOA and getting down to around last 25% or so of range? It usually lets me know the speed I need to remain below to make it to destination or nearest supercharger. Usually its somewhere 70mph or even lower. Curious, did your screen tell you to slow down slower than 80mph?
 

Ostrichsak

Active Member
Sep 6, 2018
3,323
3,275
Colorado, USA
Did you ever experience this again - the erroneous charge remaining issue? Scary especially getting stuck on the side of a highway like you did.
Nope but I sold the car that did it no long afterwards. We didn't take any more cross-country trips in that car either. There were a number of error messages once it failed and Tesla took the cheapest warranty option by claiming that the 12v battery failed which caused it. Nope. It was the opposite and the HV issue caused the 12v to go flat. Not a single indication of a 12v issue prior to all of this. I took the free 12v battery since they're wear items anyway but I suspect that HV pack may have been fixing to go south. I didn't have any other symptoms though in the limited time we owned it following so I couldn't press the issue with Tesla since there was nothing for them to replicate. Hopefully the new owner gets a brand spankin' new HV battery pack out of the deal though.
 

Ostrichsak

Active Member
Sep 6, 2018
3,323
3,275
Colorado, USA
you mentioned doing 80mph. When I've been on NOA and getting down to around last 25% or so of range? It usually lets me know the speed I need to remain below to make it to destination or nearest supercharger. Usually its somewhere 70mph or even lower. Curious, did your screen tell you to slow down slower than 80mph?
NOA?

Like I said, nothing. We travel all over the country in our Teslas as a hobby so I'm quite familiar not only with the warnings of which you speak but also of the various intricacies involved with what to do when you see them and ways to wring every last drop of mileage out of the stated range. What I'm saying is that it never once gave any sort of warning or indication what-so-ever that it was low or may not reach it's next destination which was a supercharger. In fact, as far as it was concerned, it had 2x the required range to hit the destination along the entire journey so I'm not sure how anyone could expect the car to warn that something might happen.
 

ZeeDoktor

Member
Dec 3, 2019
173
308
Sydney
NoA = navigate on autopilot. Does automated lane changes at freeway intersections etc.

You clearly had a faulty HV system in your vehicle. I don't think that makes a compelling case to discourage people to use as much of the available energy in the battery packs as possible. Your HV system could have shut down with 200mi rated rating left.
 
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Ostrichsak

Active Member
Sep 6, 2018
3,323
3,275
Colorado, USA
NoA = navigate on autopilot. Does automated lane changes at freeway intersections etc.

You clearly had a faulty HV system in your vehicle. I don't think that makes a compelling case to discourage people to use as much of the available energy in the battery packs as possible. Your HV system could have shut down with 200mi rated rating left.
Not according to Tesla.

You're welcome to do what you like. For me, I'm not pushing that envelope anymore. It's not worth the risk.

Fool me once...
 

Big Toys

Member
Jan 19, 2019
566
470
Florida
I had mine to @3% and I was milking that thing at slow roll until I could find that damned hidden charger in Miami parking garage....on the second floor.
 

Dave EV

Active Member
Jun 23, 2009
1,694
1,131
San Diego
I stopped my drive when they reached 3.0V, but as can be seen from BMS% vs Voltage plot, the BMS percentage reported looks to be set to show 0% when the still safe limit of 2.8V has been reached.
Nice data! Are the voltages above average cell voltages? At low SOC, it may be more informative to use min cell voltage, since that's what really determines how far you can drive.

I suspect that cell imbalance at low SOC accounts for most of the issues related to inconsistent range remaining as you get to the bottom of the pack, and the BMS can't always keep up, depending on when the last time the pack was discharged down under 20-30% and how you're driving.
 

r1200gs4ok

Active Member
Jul 17, 2019
1,357
454
Irvine
how can I balance the battery pack....do you run down to <20% and then charge to 100% and go drive? if you do that, how many times and at what intervals do you repeat the process and what do you look for to notice whether anything has changed
 

ZeeDoktor

Member
Dec 3, 2019
173
308
Sydney
@Dave EV that's an excellent point. Is is indeed the average cell voltage I used, and while I'm calculating the voltage spreads, I didn't log them. I'll do another run on a different route with more altitude difference to confirm results. I'll use the minimum cell voltage for that one, I'll also log a lot more information on that one.

edit: from memory, neither the cell voltage spread nor the cell temperature spread were unusually high at low SOC. voltage spread lingers around 15-30 mV in my packs, only when pressing the accelerator hard (well above 50kW demand) does it go up to 500mV.
 
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ICUDoc

Active Member
May 19, 2015
1,648
1,014
Sydney NSW
Where do you drive around Sydney at those speeds, Spachemin? A fun option would be out Hay or Broken Hill or Alice or Nullarbor way. But you'd need a flat-top truck to shadow you....
 

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