8. March 2019 by Dr. Maximilian Holland
On Wednesday night, the eagerly anticipated Tesla Supercharger Version 3 (V3) technology was unveiled, allowing the Model 3 Long Range to receive 250 kW top-charge power! It is far beyond the power levels expected by experienced Tesla tech analysts (including myself). What does this all mean? Let's dive in and discuss this new Supercharger technology.
In this article I will outline some initial analyzes of V3 and discuss some of the implications. I will see each other in a forthcoming article on what it means in practice for charging times on the way and the like. In short – Tesla obviously gives us EV technology that removes residual friction for fossil drivers who are considering making the jump into an electrifying transport life.
Estimated Load Curve
Let's dive first with a little modeling of what the load curve to model 3 long range on the Supercharger V3 might look like (and compare it to the maximum charge strength recorded on the Supercharger V2):
Let me first notice that I have called this a estimated charging curve and called the current Supercharger parameters "Beta." There are a few reasons for this: Tesla's blog article on V3 makes it clear that the company is considering current hardware and software settings to be a public beta, and it seems to "consider and evaluate" the early results before rolling more hardware and potentially customize the software and parameters next month. The other reason for sticking to "Beta" and "Estimated" labels is that the advertised (and third-party) Supercharger V3 parameters have come as a great surprise to me and to other Tesla hardware experts. A well-known and highly regarded Tesla social sector and detective (whose name we do not want to speculate on) told me "how is it possible?" Personally, I predicted top charge on Model 3 of not much over 160 kW, and "Never" more than 175 kW! I have to keep a little bit of printing on my Tesla hardware prospects from now on. 😉
The charging curve I've modeled above is based on what we know so far:
- Maximum peak power is 250 kW on model 3 long range.
- This equates to a peak of "up to" 1000 miles added per hour charge.
- 5 minute (sweet spot) charge provides up to "75 miles" of "peak efficiency" range (likely EPA city range), which is slightly less than achieved from 5 min @ 250 kW and "1000" speed (above) .
- Thus, we can deduce that 250 kW is a short peak that lasts just under 5 minutes.
- Videos (including video clips from third parties) indicate that 250 kW peak power starts somewhere before 10% charging status and 5 minute duration points to likely conical start not much over 20%.
- Videos show that the Model 3 screen estimates that charging from low levels to 80% still takes around "27 minutes" and 90% takes "35 minutes."
- Thus, we know that after the short top there is still considerable power at higher state
The curve is a decent fit for all these parameters (I have run the numbers in the nerd level detail on the spreadsheet that generated this curve). This curve (in addition to Tesla's over factoids) clearly indicates top performance ("up to") under ideal conditions. You will rarely beat all the conditions in the real world for perfect optimal charging – but if you do, the result may be something like this curve.
As mentioned above, Tesla can still adjust the parameters so far specified, based on the results of the beta testing. There are also alternative mild variants of the above curve which can provide a similar proximity to the parameters. I should add that charging from the typical 10% baseline to a high of 80% can take just under 25 minutes – significantly faster than on V2 (around 33-35 minutes). Note that the maximum recording load values on V2, as indicated in the orange dotted curve, come from the data collection and survey of our friends over to A Better Route Planner (ABRP).
As a final note on the waveform, apart from the unprecedented power level, the profile properties (especially the very early peak) take precedence over a Tesla. Check out the charging profile of the older model S 70 kWh battery pack (again from ABRP data collection):
What does everything mean?
Designing an early high peak of charging power is a smart strategy by Tesla for several reasons. Most importantly, it is the safest way to recharge quickly while protecting the battery – the power constantly returns to well-established power levels after 50% charging status to prevent battery overload.
We know model 3 Long range battery is good for 330 kW high voltage, so 250 kW (for a short period of less than 5 minutes) is within reason. Tesla now has extensive data and knowledge on the performance of these batteries over long periods of time and in various conditions and usage cases. The early peak power is more efficient, as a good deal of owners often only need a given amount of extra reach to complete the journey, and do not need to charge up to 70% or 80% or more when 40 or 50% can be sufficient .
Abandoned charging power and extra range in this way are more efficient than delivering peak current at 60-80% charging status so many other EVs are doing. This is mainly because most non-Tesla EV devices use the majority of the charge cycles on power levels that are actually limited by the maximum (amps) of the charger, and the packing voltage – which cannot be adjusted gradually – is gradual climbing throughout the load session. Battery Charging is by definition lifted its voltage back to maximum potential difference (volts). As a result, on a charger whose current is maximum for most of the charging current, it is necessarily somewhere in the second half of this session, when the voltage closes at the top. Newer and more powerful public chargers improve this by moving to much higher levels of power (ampere) delivery, up to 500 amps in many cases. This can allow some EVs to change the shape of the charging curve. Tesla designs both the vehicles and the chargers, so a more coordinated approach to this optimization task than any other EV maker can.
Amp It Up!
While we are on the subject, this is the question of current amplifiers) is the main reason for the surprise of Supercharger V3. Let me explain. The model 3 battery pack has a nominal voltage of about 355 volts. Rated battery voltage is usually somewhere near the center of full charged voltage (high) and fully depleted voltage (low). For lithium ion chemistry cells, this often varies between about 4.2 volts when full and about 3.0 volts at discharge, with a nominal value around 3.6-3.7 volts (i.e., the entire voltage range is about 15-20%). above or below the nominal value). For the Tesla Model 3's total package of 355 volts nominal, this suggests that when the voltage is exhausted, the voltage voltage is likely to be around 300 volts and when full, around 410 volts.
If this is correct, then 250 kW Power is delivered to an almost empty package whose voltage is likely to be in the range of 310-320 volts. Since the watt is a function of volt * amps, to achieve 250 kW at ~ 315 volts, the peak current must be somewhere close to 800 amps, which is unmatched for EV charge! The geek forecasts were under pressure (based on solid evidence) that Model 3 had hardware limitations of around 525 amps. Something approaching 800 amps (even for a very short peak) was far beyond expectations. Keep in mind that the designed CCS 2.0 charging specification (as model 3 in Europe is compatible with) currently drains with 500 amps. 800 is a big number and a big surprise.
Supercharger V3 hardware is apparently also capable of delivering up to 500 volts (but probably not simultaneously at 800 amps). This gives good results for future Tesla EV, which can increase package yields by 20% or so. If you are interested in the possibility of Tesla raising package voltage, I discussed this in another recent article that looks at Supercharger V3 (much of which now looks hopelessly low ball, given what has happened)! The Audi e-tron and the Jaguar I-PACE have nominal packing voltages of around 425 volts.
What more can we say about this elevated peak force? In V3, peak power is assured because system design delivers dedicated power to each stall, not kilowatts at risk of being split (and reduced) by the rear energy cabinets that need to double-duty over two stalls. Model 3 will also have a package preconditioning feature that will attempt to get the package close to the ideal high power charge temperature when the vehicle knows you are heading for a Supercharging session. This allows the package to receive higher power levels than would otherwise be reasonable (for package health and longevity).
Tesla has said it expects the average Supercharger session duration to be reduced by about half. This leads us to another reason why early peak power is a smart strategy by Tesla. The expectation of halving the average charging time is not because the average charging volume has doubled over the entire charging period (it is only double for the first 20% to 30% or so, and then gradually approaching the V2 charge regime and is not much different from V2 from 50% charge status and above). No, the prediction of average charge time is halved, because, unlike V2, early power means significant enough reach for a decent forward drive can now be achieved in 15 minutes (and then achieved again for another 15 minute break at next rest stop). In fact, on V3, longer stays are not the fastest charging strategy for drivers, compared to getting back on the road, and taking a short break later. How much range is added in 15 minutes? If the above curve is roughly correct, the model 3 long range, when starting from 10%, can add over 54% of the battery charge in 15 minutes under primary conditions. 54% translates to 176 miles of range around the city (EPA city rating) and even on the highway 54% is close to 160 miles of range (EPA highway rating) in decent driving conditions.
Front-loading of peak power is therefore not only better for the package and for trip planning efficiency, but it will also encourage people to move relatively quickly. After all, it's the finest juice in the first 15 minutes or so. Much beyond that, and you might as well go and have another quick rest for 2 to 3 hours. For people to be happy to move forward fast, it gives much more use out of each Supercharger and serves many more customers. Smart and efficient.
Supercharger V3 is more than many of us expected. With great power (amps) ability and a good development of excitement, I am genuinely very impressed with it. The power levels that Tesla has managed to push the Model 3 Long Range to, are even more surprising. We do not yet know what power the other model 3 package sizes could be charged, but there is every reason to expect that they will at least recover equivalent percentages of their total packet energy for similar charging time, if not the same absolute amounts of energy as the Long Range package. We also do not know the power levels S and X will be pushed on the Supercharger V3 (the limitation is obviously not in the V3 charging hardware, but it may be in the S and X battery packs).
Personally, I am optimistic that the batteries of 100 kWh will see a much increased charge rate on V3 (I have discussed this earlier), but perhaps not as dramatically an increase as model 3 looks. Given the latest events that exceed some of my previous predictions about V3, I'm not going to make any more forecasts right now. Let's see what more we can learn. Tesla will no doubt find a way to surprise us again.
If you see something here that does not add, or you have any thoughts about all of this, please jump into the comments.