(warning: contrarian opinion ahead)
I'm not sure if I agree with his assessment of what's happening, though I did notice some interesting behaviours later in the video. I'll explain with what my 2019 Model 3 LR AWD does. This is the first data I've seen from a heat pump Tesla, so I have a big thought dump!
On a long trip (which he was clearly on), the waste heat from the motors being dumped into the battery will maintain about a 24C difference compared to ambient (assuming no other measures are taken, like cooling via the radiator or applying heat via the motors). So for example, when it's 5C outside on a long drive, I expect to see about 29C on the batteries. If I just came off a Supercharger and the pack is closer to 60C, I expect it to drop down to about 29C eventually as well in those same conditions. This isn't my car using the battery as a "store" of heat though - it's just keeping the motors cool and the battery warm. In both summer and winter I'd say the average "passive target" temp for the battery seems to be about 35C.
So I find it interesting Tesla is happy to run the batteries much cooler now, 15-18C as Bjorn mentioned, just to suck some heat from the system. There is noticeably less extractable energy at this temp (about 1%) and more regen limitation (will vary based on SoC, but could be very significant at higher SoC). The colder battery will also tend to imbalance itself under discharge easier.
Now, regarding the points in his video:
- Sitting at 24C with 5C outside, it's clear to me that some heat was probably drawn out of the battery, yes. Cool.
- It's unclear if the battery is actively heated (motors intentionally generating heat) or passively heated (just normal waste heat from driving the motors) to that 25C point before it draws heat out, down to 15-18C. Both are possible in that 5C outdoor temp based on what I've observed in my 2019 model. It would be noticeable with the cycle time on this behaviour - longer likely means passive, which is likely also more efficient (depending how it generates heat when not scavenging from the pack).
- He's guessing it's not using the battery as a heat source at that 8 minute mark, and is "saving it for later". It lacks the data and forecasting to make that bet - I think it's more likely that it's using the air like he mentioned but temporarily, as it likely cycles between a few different modes. He was also parked, which could change its behaviour (since it can't expect passive waste heat is coming from the motors anymore, unless it actively does so). To me, this is indication that it is probably depending on passive waste heat in the point above.
- Unless I interpreted it wrong, he seemed to claim that previous Model 3s didn't precondition to around 25C at low SoC for Supercharging. That's absolutely and demonstrably false with my own Model 3. I'm guessing he just didn't have an equivalent scenario, or that his battery was already warm enough from driving and he simply didn't make a note of it (highly likely). Before heat pumps, it was easier to still have leftover heat from the previous Supercharger session, so preconditioning is less likely on long trips like he does. However with the heat pump system drawing it down to 15C, it will need to actively heat for more Supercharging sessions than the older models. Yes, that does mean the 2021 model has a scenario where it's using more power than the older models. Weird eh? It might balance out.
- He didn't mention it, but his overnight sleep it was clearly using the motors as a n actively powered heat source while parked (they're above 40C while everything else is cold, including the battery). This is strange - it would be less efficient than a PTC element like on the older Model 3s. I guessed this would be the case around and below freezing temps (it was at freezing at that point in the video), but this isn't how I thought it would work. Interesting. It's also possible that it was using this heat for something else (e.g. the battery).
I kind of wonder what a freezing cold 2021 Model 3 will do. My 2019 will actively heat the pack to about 0C, then just with waste heat from the motors after that (which takes a long time). I already think this is a massive waste of energy for short hops - I drive 4km/day right now, using 30-50km of range to do so (a large chunk of which is actively heating the darn battery just to 0C). I really, really hope the 2021 ones do not try to actively heat the pack to 15+C on similar trips just to use as a heat source - that would be a
gargantuan waste of energy for short commutes.
It's worth mentioning that I disagree with a lot of Bjorn's observations, so I have a bias already. He has a large following and has made some very false suggestions/observations (
not claims) regarding Model 3 - nothing super detrimental, but mildly annoying given his very large following that takes his word on most things.
His takeaway that the trip meter says 172Wh/km so it's done better than the previous models is seriously flawed. The trip meter does not count usage while parked. I don't doubt that it is more efficient in mild winter temps (which it seemed like he was in - heavy snow, wet roads, 0C when he woke up near noon) and
especially on long trips with lots of DC fast charging (which dumps tons of heat in the battery to scavenge). Basically, this trip of his was the best case scenario for the heat pump system.
I'd put a huge "To Be Determined" label on how it compares in daily commuter scenarios in colder temperatures.
And this concludes my wall of text / thought dump. Excited to see more data with the heat pump behaviour!