I drove a MINI E for a year, and the term we used for that was "feathering" the pedal - that's how i've been doing it on standard regen, and i've a nice 1/2 mile downhill on I-287 that yields a lovely and long green track on my energy graph. But i'm interested to see if i put it on low, if i can actually produce a deeper regen for longer with the added momentum.
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Winter Driving Experiences
- Thread starter kevincwelch
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- Driving Dynamics Model S
I drove a MINI E for a year, and the term we used for that was "feathering" the pedal - that's how i've been doing it on standard regen, and i've a nice 1/2 mile downhill on I-287 that yields a lovely and long green track on my energy graph. But i'm interested to see if i put it on low, if i can actually produce a deeper regen for longer with the added momentum.
I just look at the power meter when I head out, so I know where the regen levels are at. It's not a big deal for me.
And yes TC activates on Regen.
Oofa - not a fun experience that, especially with an extra-heavy EV! With this weather we've been sharing (Arctic temps = Canada's #1 export, lol), the black ice has terrified me because of the weight we all carry - so far i've felt the TC kick in just a few times though and it's handled fine. Down here though we haven't had more than a few inches of snow so far, so glad to get your experiences in preparation.
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JakeP
S P4996 ==> P02547
Yes, exactly! And even if Low produces a shallower green curve, the total area under that curve might be greater than under a deeper (but narrower) Standard curve. And if I remember my calculus, the area under (or in this case, above) the curve should be the total power regenerated.
I guess it's all in what you're used to. I learned to drive on a manual transmission, and I still can't get used to automatics. I'm not a sporty or power driver by any means, but to me having the regen on the gas pedal is the one which is "exactly like an ICE experience" -- seems "natural" because it's just like the engine brakiing.
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That's really nice. I was definitely worried about that because most of the cars I've driven have developed rusty rotors (very gentle braking habits, low driving rate, lots of salt and gunk on the roads). Not worried any more!
well, it's like engine braking on massive steroids - if you suddenly and fully take your foot off the accelerator, the regen force reminds me most of the first set of brakes you hit at the end of a roller coaster ride.
But rejoice neroden - you're going to get tons of feathered-regen opportunities on the hills around Ithaca! Maybe i'll swing by on my way to Canandaigua Lake to say hi!
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Why the prius can blend regen and braking, and why it is more difficult to do so in a Tesla :
Prius is front-wheel-drive!!!!!!
When regen is applied, it brakes on the front wheels. When it uses brakes, it uses the front wheels too!
The Tesla has both these braking-systems on different axels, making it verry difficult to blend them!
Prius is front-wheel-drive!!!!!!
When regen is applied, it brakes on the front wheels. When it uses brakes, it uses the front wheels too!
The Tesla has both these braking-systems on different axels, making it verry difficult to blend them!
Very interesting observation Doug_G. Wonder why TM would have set the system to use ambient vs internal temp unless the pack thermometer is exposed/close to outside and would read outside temps that it would interpret as pack temp. This is a question for the TM engineers
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Better than other RWD like BMW 3i series, same or worse?
Todd Burch
14-Year Member
This morning the temperature was about 25°F. In my uninsulated garage (which was in the 40/50°F range), I opened the car and turned on climate control (full auto, temp at 70°F). Closed the driver's door just to the first click (climate control and touchscreen stayed on).
I then spent 20 minutes finishing my morning routine, and came back to leave. A few observations:
-My range had dropped 4 miles, even though I was still plugged in.
-After hitting the road (cabin all toasty), my Wh/mi usage was up in the 400-600 range for a while.
This behavior was contrary to what I expected.
First, I didn't expect to see the range loss because I was still plugged in. Shouldn't power from the wall be used for heating up the cabin and battery?
Second, I'm not sure the pack was heated at all. I would've thought that 20 minutes was more than adequate to heat up the pack, and I didn't expect to see the pack warming after I hit the road. Does turning on climate control NOT start heating the pack?
I then spent 20 minutes finishing my morning routine, and came back to leave. A few observations:
-My range had dropped 4 miles, even though I was still plugged in.
-After hitting the road (cabin all toasty), my Wh/mi usage was up in the 400-600 range for a while.
This behavior was contrary to what I expected.
First, I didn't expect to see the range loss because I was still plugged in. Shouldn't power from the wall be used for heating up the cabin and battery?
Second, I'm not sure the pack was heated at all. I would've thought that 20 minutes was more than adequate to heat up the pack, and I didn't expect to see the pack warming after I hit the road. Does turning on climate control NOT start heating the pack?
Todd Burch
14-Year Member
I hope this improves with a future firmware update. No reason to burn miles when you're still plugged into the wall. Shouldn't be a major change--they just need to initiate charging at a rate required to offset the usage.
Right, I have some observations on this front. I had previously assumed that the pack heater would be on if the cabin heat was on. I assumed that because the message that pops up telling you the battery is cold says to plug in and to use the smartphone app to pre-warm the car, and when you do that the pack heater would also be turned on. Well, that leads to the idea that if the cabin heat is on so is the pack heater. Not so.
Today I was demonstrating the car at a meeting of the Professional Engineers Ontario, Ottawa Chapter. The practical upshot is I spent a half hour outside at -18C. Brrr!!!! The car had been cold soaked prior to this demo and had no regen.
I left the door open a notch so the heat would stay on, and when I had a chance I would pop inside to warm up. I noticed the car was drawing 5 or 6 kW for the cabin heat, which means the pack heater was NOT on. When the pack heater is on the power draw doubles. Confirming this, when I started up afterwards I still had no regen.
So, it appears that popping the door to turn on the cabin heater does NOT turn on the pack heater. You either have to be charging, or your butt has to be in the seat.
Also I have previously observed that the car NEVER draws any power from the charge cable unless it is actually charging. There is a workaround for this: set Range mode (so it will continue charging even if "full"), and set the current to minimum. You won't accumulate any significant battery charging in half an hour (or even in several hours) but it will heat the pack. Just don't forget to reset it back to normal settings afterwards.
Todd Burch
14-Year Member
Thanks Doug. I tried that this morning. Went to range mode, set to 5 amps, turned on climate control and began charging. Came back 20 minutes later, and I'd lost 3 miles of range. Guess I didn't set the amperage high enough--whoops! I'll try 20A tomorrow.
I believe this worked. Although I did have higher than normal initial usage, it dropped back to normal much quicker. And, after all, it was 19 degF when I pulled out of the garage this morning, so it's not exactly toasty outside.
Most importantly, this will be forgotten when the app comes out next week. Right Tesla? Next week, right? This app seems like it's been delayed forever!
JakeP
S P4996 ==> P02547
Well this is interesting, because I used your door-open-a-click method last weekend before my long trip, and I never received the "Battery pack is warming, power will increase as you continue to drive error". Yet my initial "Rated Range" dropoff in the first 10-20 miles of my trip (on back roads) was very high...my buffer just disappeared entirely. Maybe it was heating the pack, but I was above some threshold where the message displays. It had heated the pack just 2-3 hours before, after being cold soaked at 17F for 2-3 hours prior to that...so perhaps residual heat was in the pack, but it "topped off" the pack once I got underway, but never let me know via the message. I did have limited regen initially, IIRC.
17F isn't that cold, so I doubt it was running the pack heater full blast. From observation I don't believe it pops the message unless it's on full power. The batteries are also less efficient when they are cold, so that could have some impact.
Here's how to really find out what the pack heater is doing. Drive for a minute or so, because it doesn't seem to turn on as soon as you start the car. Pull over and stop, but leave it in Drive so it doesn't think you're shutting down, and turn off the cabin heat (use the master switch at bottom center of the touchscreen). Now look at the power draw meter on the speedometer. If the pack heater is on full you'll see a fair bit of orange - something like 5 or 6 kW. If it's not on at all you'll just see a sliver of orange.
Full pack heat plus strong cabin heat comes in somewhere around 10-12 kW. (It's hard to tell exactly as it's a logarithmic display and the tics are hard to see.)
If you're trying to maximize range, you do not want as much regen as possible:
1. Mechanical brakes are super evil - avoid completely whenever possible. Regard them purely as an emergency safety mechanism.
2. Regen is evil - you waste energy by using the motor to build speed, and you again waste energy by using the motor to reduce it. Electrical losses are somewhere around 15 to 30 %. But in addition to this, tire resistance increases dramatically when you accelerate or decelerate, because the rubber slides against the road surface, and it deforms much more too. I don't know how much this is, but I think it would be hard in practice to regenerate more than half the energy you spent, considering rolling resistance and electrical losses both ways (out of and then back into the battery).
3. If you have to brake, use regen, but do it early so you can regenerate at as low power as possible.
4. Using more power (in the physics sense, measured in watts) than necessary is bad. This is because both electrical losses and rolling resistance increase dramatically with increasing power. So to conserve energy, you want to accelerate and decelerate relatively slowly and maintain an even power consumption. Note that this is very different from maintaining an even speed. Accelerate and decelerate as though you were transporting your daughter's wedding cake unprotected in the passenger seat.
In hilly terrain, imagine that you're a rollercoaster. This is the ideal, a rollercoaster does not waste any power maintaining speed uphill, and then regenerating (or - heaven forbid - braking) downhill. Even if you avoid regenerating downhill, you will waste energy unless you simply coast over the top. On a public road, this is obviously unachievable, but it helps to know what the ideal is.
So if you're approaching a smallish hill and there's no one behind you, try to estimate early on how much power you have to apply to clear the top at your minimum acceptable speed. Then feather the accelerator so that gravity decelerates you at the rate that will let you reach the top at that speed. Then you either coast back up to speed down the other side or just keep applying the same power as during the climb to accelerate back up to cruising speed if the road is level. This minimizes the power and therefore the losses.
Turning also increases rolling resistance, so it helps to drive the racing line as much as safely possible. It's better to take the corner at higher speed if that can be done safely rather than regenerating first and then accelerating again. Hoard your kinetic energy.
Now don't take this too far, or other drivers will get seriously annoyed. Just knowing how it works helps, there is usually some wiggle room.
There are also some tradeoffs that complicate the picture if you really try hard to conserve energy. For example, accelerating a bit before you enter an uphill will get you to the top in a shorter time and reduce the required power, but this will also increase air resistance. It's hard to say where the optimum is without detailed and unobtainable data.
I don't often drive like this, but I can squeeze out quite a bit more range than usual if I have to without being (too much of a) nuisance to other drivers.
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I haven't made a real test but I *think* Model S is better than the average RWD. But RWD is still RWD.
Actually today the roads are icy and car is quite good. I was hearing other cars spinning tires and mine was doing T/C efficiently.
Johan
Ex got M3 in the divorce, waiting for EU Model Y!
All of this is very correct, I believe. Just one thing to add that I've been thinking about, perhaps relevant seeing as this is a thread about winter driving: with the currently reported behaviour of the Model S in low temperatures imagine driving a certain distance either as efficiently and carefully as you can and ening up with say 250 W/mile or driving a bit faster and caring less about being efficient and instead doing it at 350 W/mile. Now, imagine that it's quite abit below freezing. Some people have reportef that during efficient (<300 W/mile) driving at highway speeds it seems the pack gets cold and the car turns on battery heating in order to maintain battery function and performance. So say you're doing all you can to be efficient, but you are in a way penalized for being to efficient by battery heating turning om, thereby consuming i total MORE energy for the driven distance than if you were driving more leniently?
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