Tesla Max Range Estimate Seems To Shift With The Season
Originally published on the Tesla Motors Club forum.
By FlasherZ
I posted some rough data in the 90% thread and the 90D thread, but felt it might be appropriate to pull another thread here when discussing range and degradation.
It’s starting to get colder here in the midwest, and my displayed range after charge (at 90% and 100%) has been dropping again, as it has for the past few years when the colder weather rolls in. I’ve also noticed it picks back up in the spring.
So I put my database of information from my car to good use (it dates back to October ’13, data corruption destroyed the DB prior to that date) and graphed my range for both 90% and 100% charge levels.
Here are the two graphs. First, 90% (selection criteria – all points, API battery_level = 90):
Next, 100% (selection criteria – all points, API battery_level = 100 (that’s right, I am not afraid to range charge!):
As I noted in the other threads, I have not done any correlation with temperature, distance from range charge / rebalance, or software updates. I did go back and look at the anomaly that occurred on late Feb, 2014, when the graph does a correction upward. After thinking about it – this was the date that my rev A battery pack was replaced with the refurbished rev D pack following the contactor failure.
Note that this is not the same thing as the snowflake that “reserves” some range in ultra-cold temps – this is the car’s interpretation of the range of the battery.
Conclusions to reach here: range display is seasonal and as you enter winter months, you may not be experiencing the degradation that you think is appearing… it’s likely that it comes back in spring.
Addendum (in Response to a Question/Request)
Here’s what a moving-average overlay looks like. Blue is 2/25/2014-2/24/2014, Green is 2/25/2015 onward:
Another view… here is the monthly average range at 90% charge (mean of all values within a month beginning with the date on the X axis). EDIT: I completely forgot I had an easy source of comparison with regard to temperature. I have the car’s “outside_temp” data. Here’s an overlay of the average outside temperature (as registered by the car, deg C, unheated garage) with the average range:
One more — the full data series for range vs. temp, rather than average. There are roughly 55,000 temp samples and 11,000 90% range samples over the time period:
In a quest to find tighter correlation, I did some more work. This time, I pulled temperature samples only within 30 seconds of the 100% SOC range samples I had pulled.
The correlation is now tight, with only two explainable areas of disconnect: 3/2014, just after the new pack had been installed; and 8/2015, just after my car’s energy data had been reset due to the accident repairs from colliding with a deer.
Reprinted with permission.
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so what happens if you do run out of juice on the highway
can you walk to the nearest recharge station, and buy a portable battery, walk back and plug it in
does the AAA towtruck have a quick roadside recharge option if you call them – the jumper cables of the future
can a passing motorist give you a boost
…or what
The car will simple tell You to charge prior to such a stupid incident
I think your first option will be the closest. For now it is only intelligent people buying electric cars so it will be a while before the idiots have them in enough numbers for it to be a problem big enough for actual solutions to become common.
Most likely there will be a hand carriable backup battery you would take to some recharge place. Of course the auto drive features by then may just take over and force you to a charge point before you get out of range.
Here in Arizona we have AAA providing roadside emergency EV charging. Basically, it’s a tow truck with a diesel generator connected to a CHAdeMO plug that provides about a spare mile per each minute while hooked up, with the idea that about 15 minutes (miles) will get a stranded driver far enough down the road to find a stationary EVSE. One of the drivers I talked to told me that such emergency calls are extremely uncommon. Most EV drivers, apparently, know the range limitations of their cars and plan their trips accordingly . . .
http://1.bp.blogspot.com/-79biV5LlBmE/UlIQT2Nq56I/AAAAAAAAAM8/Eir5cWMZdBo/s1600/13_030_W.jpg
There should be no excuse for running your batteries flat. With today’s technology your EV should alert you to the need to stop for a recharge and guide you to an available charger.
For the knuckleheads who can’t follow instructions there’s the simple solution of the recovery truck. Winch your car onboard and haul you to some place to charge. Who pays for your stupidity will be between you and your insurance company.
There should be no excuse, however if you’re counting on a charger to be available and it’s out of service when you get there, in many areas of the country that can leave you stuck, or next-thing-to-stuck if it’s a low-power L2 charger.
We should soon evolve past that problem. Over the next few years as production of EVs ramps from a few tens of thousands per year to a million or more per year chargers should be found in large numbers. And communication between individual cars and chargers should appear. Most likely you will drive (or your car will drive you) to a charger that has been reserved for your use.
The only problem might be that the grid might be down. But that also takes down gas pumps as well.
I saw a post on the Tesla forums from a person who bought a Model S in Seattle, WA: http://my.teslamotors.com/it_IT/forum/forums/driving-model-s-alaska
Here in Arizona we have AAA providing roadside emergency EV charging. Basically, it’s a tow truck with a diesel generator connected to a CHAdeMO plug that provides about a spare mile per each minute while hooked up, with the idea that about 15 minutes (miles) will get a stranded driver far enough down the road to find a stationary EVSE. One of the drivers I talked to told me that such emergency calls are extremely uncommon. Most EV drivers, apparently, know the range limitations for their cars very well and plan their trips accordingly.
Depending on were you live ICE models have the same problem, reduced mileage in winter. Some of the reduction comes form the temp, others road condition (snow) and changes in fuel (so I am told)
As for running “out of fuel” on either ICE or EV, if you do not look at the gauge and know what range you have left, nobody can help you.
This. My 2nd-gen Prius used to average ~ 40mpg in January and February, which knocked 50 miles of range off a tank. Driving in snow could reduce that further, as low as 35mpg, now we’re doing 100 miles less per tank…
I see the opposite for mileage. I get more mpg in the winter than summer because they change the gas to the winter blend and I don’t have the a/c blowing full blast.
You must be living in the southern parts of the US, I live in Canada and some northern parts of US get snow as well.
The range vs temperature plots would be more informative as scatterplots with the temperature on the x-axis and range on the y-axis
If the car is charged in an insulated garage, would that make a difference? Or are all of these graphs based on the time the vehicle spends out of the garage irrespective of how it is charged?
Charging produces some heat. If that heat is retained in an insulated garage then some range is going to be maintained.
What I’d like to see is a comparison of range for same model EVs with and without the batteries (and cabin) being pre-heated while still attached to the grid.
Batteries give off heat while discharging. Seems like if you started out with warm batteries you range shouldn’t decrease due to ambient temps, or at least not much. After parking all day in the cold there could be a loss.