Top 10% does not provide as many miles?

[gavine]

Thank's. I figured it must be something like that but I'm new enough to the car that I jump whenever I see a warning icon.

Usually, when there is a warning icon, you will have a way of finding-out what the message is. At least on the S/X, there is a red exclamation point at the top of the console screen for any errors showing on the binnacle where you can tap to get the message. I'm not sure on the Model 3.

 

[ajdelange]

That's good to know too. Question is whether I'll remember it. Does that alert stay on until you check it or fade after some time?

 

[mxnym]

Usually, when there is a warning icon, you will have a way of finding-out what the message is. At least on the S/X, there is a red exclamation point at the top of the console screen for any errors showing on the binnacle where you can tap to get the message. I'm not sure on the Model 3.

That isn't the case for the warning icon on the regen end of the IC consumption meter. I actually tried to get support and the service center to tell me what triggered it, and never had any luck getting a response from either of them. jerry33's explanation may be accurate, but it also comes up when there are still dashed lines, and it always disappears shortly thereafter (or it always disappeared even while the dashed lines remained last year, I haven't paid a lot of attention this season). My best guess is that it means the max regen level has been adjusted, because usually you can see some sort of movement in the dashed lines right when it comes up.

 

[wycolo]

> In those cases I was lucky to get 500 Wh/mi mileage for those initial miles. [OP - gnuarm]

Don't rely on initial wh/mile readings: they begin every new trip ~750 and then settle down to eventually become usable information. Twenty miles could be too soon for anything but delta indications.
--

 

[ajdelange]

That's exactly the kind of behaviour I saw. Knowing that this warning does not presage the rear motor falling out within the next half mile is a comfort!

 

[ajdelange]

Don't rely on initial wh/mile readings: they begin every new trip ~750 and then settle down to eventually become usable information. Twenty miles could be too soon for anything but delta indications.
--

They are always useful if you know how to interpret them but it takes a while to figure out how to do that and its easier for an engineer than for a poet. If Tesla isn't going to tell us in the manual then someone should write a Tesla for Dummies book that does.

 

[gnuarm]

Yes it is. Example: the Nernst Equation - E = Estd - ((R*T)/(n*F) )*(activity_reduced/activity_oxidized)

Estd is the voltage produced in some standard state, R is the gas constant, T is the temperature in Kelvins, n is the number of electrons transferred, F is the Faraday constant and the acitivites are those of the species in the reduced and oxidized states. Look familiar?

Maybe I should have written that as, "Isn't R the ideal gas constant?" There was no value in adding that to the post.

 

[gnuarm]

To the best of my knowledge, the car will not heat the battery while off, it will let the battery freeze and the next connection will have to heat the battery above freezing before it can start charging.

What exactly is your knowledge on battery heating? Many others here have posted that the car will maintain some minimum battery temperature when parked at least until the battery charge drops too low. But maybe I misunderstood and they were talking about being connected to a power source.

Also, you don't get full regeneration at 99% battery, you might get some regeneration, but maximum regeneration exceeds 60kW and the battery can not handle that much power in the upper 90%s. I've not paid attention to the exact percentage that full regen returns, but I've had partial regen when charged to 95-96%.

I don't know for a fact regen is not limited all the way down to 90%. This time of year I can't test it either. Once the weather warms up I will check that.

I also wouldn't underestimate the impact that regen has on range. I've had my 30 mi efficiency improve by between 25 and 30 Wh/mi when exiting the highway at 70+ mph and letting regen recover all the energy it can. That's enough power to cover between 2 and 3 miles cruising.

Sure, regen has a huge impact on range and from what I can tell, is the single largest effect that makes EVs more fuel efficient than ICE autos. That's not the question. The question is how regen is limited in the top 10% of SoC. Even if it is slightly limited, that isn't a large effect unless you are prone to heavy engine braking or let the autopilot slow the car which does have a heavy foot.

I suspect it might have to do with a combination of lower regeneration combined with the fact that you're only going to be at full charge at the start of your trip, where you're expending the most energy to get back up to cruising speed.

Huh? I don't typically drive from my house directly onto a highway. I am typically anywhere from 2 to 30 miles from a high speed, no braking highway.

 

[aesculus]

Getting back on topic: I only have one situation where I was suspicious of what the OP is describing. It was a 70F day, no wind/rain and a flat road for 60 miles. Supercharged just before leaving. I don't have any evidence of the situation but remember thinking the SoC seemed to be dropping very rapidly from the 99% I charged to until it stabilized in the low 90's. At the time I just thought it was odd.

The few other times I have charged to 100% had way to many other variables to consider such as climbing, super low temperatures, range mode, winds ...

 

[Krazaak]

What exactly is your knowledge on battery heating? Many others here have posted that the car will maintain some minimum battery temperature when parked at least until the battery charge drops too low. But maybe I misunderstood and they were talking about being connected to a power source.

I know it lets the battery get below freezing for sure, I don't know if there's some low limit where it will finally kick in the heat. I'm not sure if it will maintain temperature while plugged in directly or if that's simply a byproduct of charging periodically keeping things warmer or heating to charge. My garage doesn't get below freezing, so I've never had the blue snowflake show up, but it's been cold enough that I've driven 20-30 miles without getting full regen back. I did disable smart preconditioning though to limit vampire drain, since my driving schedule is very random.

People make a lot of assumptions, many of them wrong. I'm only sharing what I've personally experienced or noted where I'm guessing. I haven't noticed any different in the top 10% of my battery that I didn't attribute to less efficient driving.

 

[ajdelange]

People make a lot of assumptions, many of them wrong. I'm only sharing what I've personally experienced or noted where I'm guessing. I haven't noticed any different in the top 10% of my battery that I didn't attribute to less efficient driving.

Amen to that and give4n the paucity of reliable information from the manufacturer we don't have a lot of choice.

Here is what I assume is happening with the battery. Lithium cells have low internal resistance so that they don't get much heat from current flowing into or out of them. They are more sensitive to damage from excessive charging current than excessive discharge current so charging current is limited more than discharge current when the battery is cold.

There is obviously motivation to charge the battery as quickly as possible. When connected to an AC charger about 10% of the power going to the car is converted to heat in the rectifiers. The rectifiers sit on cold plates on the coolant loop and so this heat is available to warm the battery as it's on the coolant loop too. When charging with the 14-50R mobile charger the current draw is limited to 32A which is 7680 Watts @ 240 V. Ten percent of that is 768W that's not a lot of heat. Even an X with the 72A charger draws 17.280 kW 10% of which is 1.72 kW. That's still not a whole lot. The battery heater in the coolant loop is reported to have from 4 - 6 kW capacity and clearly that is how much power is required to heat the battery in timely fashion. When connected to an AC charger the Telsa engineers have the choices of relying on waste heat from the rectifiers to heat the battery thus sending all available charging current to it or to cut in the heater initially so as to get the battery able to accept the most charge most quickly or anything in between. I won't speculate on what they actually do as I haven't a clue.

When at a Super Charger the rectifiers aren't used, there is no waste heat and the strategy in this case would clearly be to use the battery heater to the fullest extent possible,

When the car is running you clearly do not want to be using the battery heater if you don't have to and as the discharge current limitations are less restrictive than the charging ones you don't appear to have to unless it gets really cold in which case restrictions draw appear and the battery heater may come on. In the maximum performance mode the battery heater (or heat pump) is used to keep the battery in the requisite band for best performance.

In cold but not extremely cold weather the waste heat from the inverters (and maybe the motors?) is used to heat the batteries. If you are getting 350 Whr per mile at 60 mpH the implied power draw is 21 kW making 2.1 kW (or less if no heat is recovered from the motors) available to heat the battery with the motivation being to allow it to accept regen current. That's not a lot of power and it can take a good long time for the regen limitation lines to disappear when the temperature is around freezing. Is the battery heater used? Perhaps. A 4000 watt draw by it would add, at 60 mpH, 67 Whr/mi to the usage numbers.

That's the picture I have come up with based on my observations.

 

[wycolo]

I don't want to waste (@100% rate) any battery power in order to heat the battery just so I can enjoy regen which only is 80% payback. I'll simply use the brakes and it is a good thing to use the brakes which keeps them functioning properly. Granted someone may have a unique commute where this issue becomes a PIA each winter so yes, they will gladly pay the cost to support full=time regen.


> its easier for an engineer than for a poet. [adjdelange]

wh/mi readings are no big deal; under 400 is very good for high speed travel with dry/no wind,
under 300 is very good for medium speed with dry/no wind.
--

 

[ajdelange]

It's been said here recently a couple of times that regen doesn't seem get the credit it deserves. Depends on how much braking you do and the terrain. Driving in hilly country I would definitely want it.

I don't think there is anything you can do to turn it on when driving except go into max performance mode which will cost you range. If your goal is to maximize range I would suggest either that you warm the battery at home by turning up the heat in your garage, putting some unit heaters near the car or going to the nearest supercharger on your route as that will kick on the battery heater if your battery is cold.

As for Wh/mi being no big deal: you haven't met my wife (a fine lady).

 

[Krazaak]

I don't think there is anything you can do to turn it on when driving except go into max performance mode which will cost you range. If your goal is to maximize range I would suggest either that you warm the battery at home by turning up the heat in your garage, putting some unit heaters near the car or going to the nearest supercharger on your route as that will kick on the battery heater if your battery is cold.

I've enabled max battery power to heat the battery up for trips where range was going to be an issue, but only while connected to shore power. It negates most of the penalties associated with low temperature, but I'm positioned well for supercharger access, so range is rarely a concern. The only time I would consider using it to warm the battery off pack power would be before driving down from the mountains, just for the convenience of being able to use regen instead of the friction brakes.

 

[ajdelange]

I've enabled max battery power to heat the battery up for trips where range was going to be an issue, but only while connected to shore power.

Can you do that in a D?

 

[Krazaak]

Can you do that in a D?

I'm fairly certain that only the performance models can manually heat the battery.

 

[ajdelange]

That's what I thought. Clearly what you suggested is the most convenient way to leave the house with a warm battery - if you have a P.

 

[jerry33]

That's what I thought. Clearly what you suggested is the most convenient way to leave the house with a warm battery - if you have a P.

P or not:
1. Range mode off when charging. (I wish it turned off anytime the car was plugged in, but it doesn't)
2. Set the timer so that the charging finishes around the time you are going to leave.
3. Depending on the weather, twenty to forty minutes before leaving, turn on the heat from the app and set it to high.
4. Before driving, turn range mode off. Depending upon the length of your drive, also turn the heat off for best range. Use the seat heater if necessary.

All this is temperature dependent. In extreme cold, skip point #4.

 

[gnuarm]

P or not:
1. Range mode off when charging. (I wish it turned off anytime the car was plugged in, but it doesn't)

What does range mode do when charging???

2. Set the timer so that the charging finishes around the time you are going to leave.
3. Depending on the weather, twenty to forty minutes before leaving, turn on the heat from the app and set it to high.
4. Before driving, turn range mode off. Depending upon the length of your drive, also turn the heat off for best range. Use the seat heater if necessary.

Isn't that then range mode always off???

All this is temperature dependent. In extreme cold, skip point #4.

 

[Krazaak]

What does range mode do when charging???

Isn't that then range mode always off???

I assume he meant range mode on while driving.

My understanding is that range mode on disables the battery heater, so that the battery warms only by waste heat, instead of the dedicated heater. It also limits how much power is used for either heating or cooling the cabin.

I don't know how much it impacts actual range though. In theory, for local driving having the battery heat up faster so you can get more regen might be beneficial; for a highway trip where regen doesn't matter as much while cruising, letting the waste heat warm the battery is probably sufficient.

P or not:
1. Range mode off when charging. (I wish it turned off anytime the car was plugged in, but it doesn't)
2. Set the timer so that the charging finishes around the time you are going to leave.
3. Depending on the weather, twenty to forty minutes before leaving, turn on the heat from the app and set it to high.
4. Before driving, turn range mode off. Depending upon the length of your drive, also turn the heat off for best range. Use the seat heater if necessary.

All this is temperature dependent. In extreme cold, skip point #4.

I never even considered the effect of range mode while charging. If it prevents the battery warmer from coming on while plugged in to charge, that's asinine. You can't charge the battery until it's been warmed up below freezing. If range mode disables heating the battery, does it just sit there forever?

I've never been happy with the results of using range mode, but I suppose it could make a significant difference on a cold soaked battery if you have a long way to drive before charging. If you don't need the regen, you can live with potentially limited power output and you're an hour or more away from charging, there's no sense in burning energy just to warm the battery. Waste heat will eventually do the job.