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Rated range stopped going down at 9
- Thread starter walla2
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- Driving Dynamics Model S
ChadS
Last tank of gas: March 2009
Hmm...
1. you were going down a mild hill
2. you had a great tailwind
3. you really were losing miles and came very close to not making it, but you had a bug that caused the display to stop updating (didn't somebody report that once?)
4. physics violation!
5. the number of miles left is really a guess based on the voltage and a bunch of other factors. It could have decided the guess was overly pessimistic; Tesla does seem loathe to suddenly add range though, so you often just see the miles sit in the same place for a while
6. cold soak recovery? Nah, it probably wasn't that cold to start, and you would have warmed up and seen the recovery sooner
1. you were going down a mild hill
2. you had a great tailwind
3. you really were losing miles and came very close to not making it, but you had a bug that caused the display to stop updating (didn't somebody report that once?)
4. physics violation!
5. the number of miles left is really a guess based on the voltage and a bunch of other factors. It could have decided the guess was overly pessimistic; Tesla does seem loathe to suddenly add range though, so you often just see the miles sit in the same place for a while
6. cold soak recovery? Nah, it probably wasn't that cold to start, and you would have warmed up and seen the recovery sooner
None of the above occurred except maybe the physics violation. It was odd. I'm on 4.3, and this was first long trip. The fact that I had 5 kwh left means I had about 20-30 miles likely left even at 9.
Todd Burch
14-Year Member
Did you charge back up to a standard or range charge? How many miles were showing after you recharged?
Battery charge monitoring is an inexact science complicated by external factors, both environmental and user-induced, that the car must make estimates regarding.
Battery SOC (state of charge) at any given moment is going to be based on voltage/current at that instant. The car then has to extrapolate that in to a distance estimate based on your current power usage, temperature, expected non-linear performance of the battery, etc... In other words the car has to guess that what WILL happen based on what HAS happened in a constantly changing environment.
It's much the same reason that the trip-computer "Distance to Empty" displays are notoriously inaccurate.
I'd guess that the S is constantly refining the "discharge slope" of the battery SOC and modifying the distance estimate based on that. For "conservative" reasons they may have been hesitant to have that slope go int he positive direction except when in active regen... so it may level out for a bit if the car is consuming power at a less-than-projected rate.
I expect they don't want to give anybody false expectation they can go farther than might actually be the case based on some short-term power fluctuations and have somebody drive past a charging opportunity they should have taken.
Battery SOC (state of charge) at any given moment is going to be based on voltage/current at that instant. The car then has to extrapolate that in to a distance estimate based on your current power usage, temperature, expected non-linear performance of the battery, etc... In other words the car has to guess that what WILL happen based on what HAS happened in a constantly changing environment.
It's much the same reason that the trip-computer "Distance to Empty" displays are notoriously inaccurate.
I'd guess that the S is constantly refining the "discharge slope" of the battery SOC and modifying the distance estimate based on that. For "conservative" reasons they may have been hesitant to have that slope go int he positive direction except when in active regen... so it may level out for a bit if the car is consuming power at a less-than-projected rate.
I expect they don't want to give anybody false expectation they can go farther than might actually be the case based on some short-term power fluctuations and have somebody drive past a charging opportunity they should have taken.
Todd Burch
14-Year Member
That's what I was guessing might happen. When the battery is closer to empty--then filled up--the range indication seems to be a little more accurate. I think over normal use (for example, daily discharge from 90% to 65%, then charge back up to 90%) the range remaining indication decreases faster over time than the actual battery degredation, and drawing down to a few miles of range remaining allows the algorithm to correct itself a bit.
BTW...I've never had more than 242 on a standard charge. I show 240 right now. I've never been below about 100 miles rated remaining, after 7,000 miles of driving. If I were to drive down to just a few miles and recharge, my guess is that my standard charge would show something closer than 242, or maybe a little more.
Ah, range calculation algorithms....
ChadS
Last tank of gas: March 2009
Are you sure it's not #5, the car recalculating remaining energy as the battery gets low and it gets more detailed information about the battery's state? Like scaesare, I think that is the most likely cause. Unfortunately it's also almost impossible to verify without Tesla giving us more information, so there's no way for us to be sure.
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