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The Model 3 uses the rear motor to generate heat - up to about 4kW apparently. It is a very clever system.
Clever for reducing the component count in the car, not clever for performance, if you're trying to heat the cabin. Whether the heating is done in a dedicated heater element or in the windings of the motor, it is still a resistance heater.

Furthermore, it is considerably less efficient than using an air space resistance heater due to the huge thermal masses and delays involved.

If your resistance heater is just coils of nichrome wire in the air flow coming into the cabin then when you turn the heater on the coils of wire have extremely low thermal mass, heat up almost instantly and put out hot air immediately. That's basically the same as a fan heater.

If you heat the motor windings on purpose there is a large thermal mass of motor that has to be heated before the coolant flowing through it starts to warm, that coolant loop itself has considerable thermal mass and heat transfer rate is limited by the rate the coolant is pumped around the system. You then have to pass that coolant through a heater matrix if you want to use it to put warm air into the cabin. To get any sort of effective heating you need a coolant temperature of at least 50-60C.

So as a means of heating the air in a cabin it's really poor. This is one reason the heater in my Ion is so crap - it does more or less the above except swap the motor for a PTC heater. It has a PTC water heater that heats coolant in a coolant loop that is pumped through an old fashioned ICE heater matrix. It takes ages to heat up (5-10 minutes) and cool down, and there are a lot of heat losses from the heater itself (mounted under the car) the pipes etc. In short its very poor compared to an air space resistance heater let alone a heat pump.

Where the waste heat from the motor could be usefully used would be to warm the battery however. The heat is already available in liquid format ready to be pumped around the coolant channels in the battery, and the target temperature you want is much lower than that required to heat cabin air effectively. The Model 3 does in fact use excess motor heat to heat the battery.

It's still not as effective as a dedicated PTC heater (as used in the Model S / X) for pre-heating however, due to much larger than necessary thermal masses and the fact that some of that energy is being radiated from the motor into the outside world. So not ideal from a pre-heating perspective (deliberately heating a stationary motor) but a good idea for recovering waste heat once the motor is warmed up naturally from driving.
 

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Cold soak of the battery over multiple days in winter is a problem for all EV's. Battery thermal mass is high and batteries are fairly well insulated from the elements when the car is parked (and especially from a cold clear night sky, which causes most heat loss from a car over night) so if you drive the car every day the use keeps the cells considerably above ambient temperatures.

For example I find on my Ion that I can have a -5C clear night in winter but because the car was driven the previous day and then put on charge in the evening (which also continues to warm the cells for many hours) the cell temperatures in the morning are still around 10-15C above ambient and this really helps minimise losses.

However if I let it sit for the entire weekend without use the cells can fall much closer to ambient and then the cold battery depature tax can bite a lot harder, especially as it has no battery heater of any sort.

I have a few thoughts on that...

1) If you don't have a heat pump you're still leaving performance on the table especially in a UK climate. The Model 3 is already a very efficient car (especially at speed) but the winter performance is still beaten by the likes of the Ioniq, and the reason is probably in good part the lack of a heat pump. Why leave performance on the table for a marginal cost saving, especially if you're trying to build or maintain the reputation of being the company that makes the best EV's around ? At least make it a buyer selectable option and see if buyers go for it or not. I suspect the constant drive to meet the fabled $35k target is ultimately what caused the heat pump to be axed as "non essential", not because it wasn't worth it or because there were technical challenges in fitting it into the design.

2) Short journey efficiency does matter - for anyone who does not have at home charging and will be forced to follow the ICE weekly "fill up" model. One reason to buy an EV with as long a range as a long range Model 3 is that you could charge once a week and commute for a week using it, without having at home charging. And lets face it, a lot of people don't and can't have at home charging, yet will eventually be forced to drive EV's.

These (EV Naive) people might reasonably expect that they could achieve say 250 miles of range while doing five 40 mile a day commute trips each week. If the winter depature tax is very high due to lack of AC assisted pre-heating (no home charger) and lack of a heat pump to get the cabin warmed up efficiently, they're going to be disapointed by the range they actually do get. Something with a heat pump that could even share the heat pump output to heat the battery is going to fare far better here in the many shorter trips from one charge scenario, and I think this is going to be a very common scenario.

3) Even if you have a lot of range available, if the penalty in terms of percentage range loss is high due to heater use it's inevitably going to cause you to be miserly with the heater. Or plan two alternative charging stop scenarios if you're not sure whether you're going to need to use the heater much or not on a given journey. Sometimes the required heater use is quite unpredictable.

As the driver of a short range EV with no heat pump I find it an extreme chore to have to balance range against heater use in my on-trip mental calculations. A heat pump reduces the penalty to the point where its significant but not huge, and is much closer to the care free use of a heater in an ICE. And for that reason I've made it a priority to choose an EV with a heat pump - regardless of what battery size it may have - as my next purchase.

Sure, a Model 3 has a huge summer range so heater or not I would have loads of range left at the end of a day and I can charge at home. So the lack of a heat pump would not affect me on commuting or short trips. However as soon as I started planning long trips that would require charging I then have two significantly different "ranges" to consider when thinking about charging stops... a no heater range and a heater range that are considerably different.

So the same issue returns, just for longer trips. With the heat pump the penalty can be (theoretically) only about 1/3rd as much and be small enough that the extra consumption of having to use the heater unexpectedly on a longer trip is not going to cause you to have to reconsider your charging stops as it will be small enough to be taken care of by the safety buffer you already included.
Interesting points, thank you. Makes sense to me. However, I have no intention of buying a nice car and not using the climate control. One of the attractions of the car. Out of interest I might try a longer journey in the car to see if I can detect a difference but the climate will stay on afterwards! I’m also fortunate to have a home charger.
 

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Valid and well-argued points as ever @DBMandrake

The Model 3 does have a resisitive cabin heater - the motor windings are used for battery heating, not cabin heating (and I've seen it take over 70 miles for the battery to come up in temperature enough to provide full regen after a proper cold-soak).

In the current winter weather I'm getting around 300Wh/mi for my 12.5 mile (each way) commute, which is not drastically different to what my leaf did (3.7mi/kWh annual average, so 3.3 in winter was entirely plausible) in similar weather conditions. I would regularly use full performance in each vehicle (sliproads, exiting a motorway regulation roundabout). The Leaf is not a notably efficient EV however, and it's true that something like the Ioniq would probably use less energy under the same conditions. I have certainly found the 3 to settle down to a much more efficient level on long journeys than the Leaf ever could.

And I agree with PaulD. Why buy a Model 3 to not use the heater to save literally 0.1p/mile? Why buy a model 3 and not enjoy its performance and handling?
 

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Lost 8.5 miles from 5am to 7pm when idle. About 10 hours parked up. ? 12% phantom drain according to Tezlab. Found a solution now plug it in every night and don't look anymore.
 

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Lost 8.5 miles from 5am to 7pm when idle. About 10 hours parked up. ? 12% phantom drain according to Tezlab.
I think one thing that you might usefully do is look at it after a couple of hours. I think that the vast majority of what you're seeing is the initial idle (my car doesn't go to deep sleep for about 30 minutes after driving) and the battery going cold (2-3 hours, depending on weather conditions and previous drive). In other words, your "8.5 miles" (which I guess to be about 2%) drop all happens in the first 2-3 hours and then it settles down to a very low rate.

Found a solution now plug it in every night and don't look anymore.
Yup.

I don't - I plug in every 2-3 days for a couple of hours on 11kW, and keep the battery in the 30-80% range typically. I keep the display on % and not going nuts over "OMG MY DISPLAY SAYS 1 MILE LESS TODAY THAN YESTERDAY OMGOMGOMG", which seems to be half of what's on the facebook groups any more.

Btw, the drops will be much less in summer.
 

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I don't - I plug in every 2-3 days for a couple of hours on 11kW, and keep the battery in the 30-80% range typically. I keep the display on % and not going nuts over "OMG MY DISPLAY SAYS 1 MILE LESS TODAY THAN YESTERDAY OMGOMGOMG", which seems to be half of what's on the facebook groups any more.
LOL.

I think people need to realise they haven’t bought a car, they’ve bought a sentient being that needs to be kept alive.
 

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I think one thing that you might usefully do is look at it after a couple of hours. I think that the vast majority of what you're seeing is the initial idle (my car doesn't go to deep sleep for about 30 minutes after driving) and the battery going cold (2-3 hours, depending on weather conditions and previous drive). In other words, your "8.5 miles" (which I guess to be about 2%) drop all happens in the first 2-3 hours and then it settles down to a very low rate.



Yup.

I don't - I plug in every 2-3 days for a couple of hours on 11kW, and keep the battery in the 30-80% range typically. I keep the display on % and not going nuts over "OMG MY DISPLAY SAYS 1 MILE LESS TODAY THAN YESTERDAY OMGOMGOMG", which seems to be half of what's on the facebook groups any more.

Btw, the drops will be much less in summer.
Your probably right, it's just took by surprise, I keep forgetting it has to feed the super computer inside for a little bit.
 

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YMMV may vary but I found that having the climate system left in manual, not auto, with AC button off, has made a substantial difference to vampire drain. I have zero explanation for this but may be worth a go?
 

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Lol.

Just given me visions of Trapdoor, and The Thing Upstairs. "Feeeeeeed Meeeee"

This may make sense only to those in a certain age bracket.
Gonna rename mine Tamagochi ??. ?
 

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I have just checked my Model 3 stats from birth..... pretty good?

5442 miles covered
1783 kWh used
3.05 kWh per mile

:D
 

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hi not sure if its the weather being bit warmer but mine went down one % from 55 too 54 but then in morning was back up too 54 and this morning noticed its lost nothing over night
 
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