I recently did a trip from Bay Area to Bend, OR and back. If I timed the arrival at the V3 SC’s right, with about 10-15% SOC upon arrival, I could hit the 250KW and 1070mph charge rate no problem each time. Yes, it only lasted about 10-12 minutes for charging time and then went down to about 670mph for the rest of my session, but I didn’t stay till full. The last one I did, I arrived at the SC with 48 miles on the battery (2018 LR M3) and it held for 10 minutes, then tapered. I don’t recall the car doing it’s normal pre-conditioning on the nav, but the OUTSIDE temp was 105 at the time anyway, so there might not have been a need to pre-condition. In 16 minutes the car added 197 miles which was all I need to easily get to home. I find that a pretty good charging rate and totally acceptable for our travel needs.
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250kW supercharger disaapointment
- Thread starter T3SF
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masotime
Member
Do you know how much time you spent charging overall? If you use TeslaFi it should have the stats.
masotime
Member
I mean across the entire trip from Bay Area to Bend, OR. Or are you saying you charged only once, for 17 minutes? How much % gain did you get over 17 mins?
Thanks for the answers! This is useful to figure out the optimal fast charging strategy for the shortest trip time.
sperkin
Active Member
It depends on what's around the charger too. When a charger is rated 250kw it doesn't mean it will hit it all the time. When a concert or sporting event nearby that uses a lot of power the charging rate drops. Kind of like your home wifi.i get 250 some time and some times only 150-200.
Same charger, but different days.
Same charger, but different days.
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It's my understanding that local load can cause a few percent voltage sag, but certainly not 20-40%. The battery charge rate is very sensitive to the battery temperature. I think you're experiencing lower charge rates due to your battery not being hot enough.
There's a misperception that highway driving and/or preconditioning is all that is needed to heat the battery so that it will reach 250kW. That is most definitely not the case. The ambient temperature is a key component. Mild and colder days will make it hard for the car to heat the battery sufficiently. Remember, it's heating ~1000 lb battery to over 100 F. That requires a lot of energy when it's not hot outside.
Not sure it's external events. The site transformer has a capacity and I'm not sure it has regulators. There's a misconception that V3s are not shared... The transformer for 4 stalls cannot provide 250kW to all 4. There's often a battery involved, and a bus to redistribute power between stalls, so that it doesn't happen often that you are limited. But it can happen, if the site has been very busy and the battery is depleted. From what I've read around...
There is defintely a total SC site capacity that depending on the site could certainly be LESS than # of SC’s x 250kWh. At kettleman for example I know we’ve seen ppl showing up there when the site is very full and not getting the 250kWh for more than a couple minutes, even with very low SOC due to overall electricity load being throttled or spread across the entire SC. With a smaller V3 location, this MAY be less of an issue, but probably even though the load between two SC towers isn’t balanced or spread, across all SC units at one station it certainly seems like it could be.
One should never expect to get more than 250 kW (not kWh) for more than a brief period of time. The longest I’ve seen 250 kW is just shy of two full minutes, which added 7 kWh to the pack.
As battery sizes increase and cell designs improve (Cybertruck, new Model S & X), maximum speeds will be realized for longer periods of time.
This is the fact most people are missing. Tesla, like Gretzky, skates to where the puck will be, not where it is. The V3 Superchargers are a clear example.
Today, we can enjoy the lack of sharing as being the best benefit of the V3 Superchargers. The high-speed is more of a party trick for now.
So basically when you get over 70% charged, it doesn’t matter if you are at a 250kW, 150kW, or 75kW. They all would charge according to the curve at the same decreasing rate.
I hope so, but doesn't that mean Tesla will have to aggressively cool battery cells, even more so than they do now?
Yeah they’ll probably have to increase the size of the air conditioning compressor to deal with the additional heat from faster charging.
Yeah, I'm not too concerned about the power consumption but the system has to be engineered to handle it. I'm not questioning Tesla's engineering abilities, but IMO it'll be more difficult to cool the 4680 batteries due to the longer path the heat has to travel. Maybe I've missed something.
Don't forget, however, that LiFe batteries have much lower internal resistance and can charge at faster rate longer than many other chemistries. We'll probably see less aggressive charge tapering with them than we do with the current chemistries.
Also, when the Cybertruck comes out with its huge battery, it will be able to charge at 250KW for as long as the current batteries charge at 150 kW, before tapering off.
Its all part of the growth from great, asymptotically toward perfection.
Per Tesla's presentation at battery day, the tabless electrodes in the 4680 cell design facilitate heat conduction to the ends of the cell which allow a 4680 cell to charge as fast as a 2160 cell (see graph below). So while many people mistakingly think 4680 cells will inherently allow faster charging, that should not be expected at the same pack size.
However, the 4680 cells in a structural pack will allow higher pack energy density (more kWh's per volume). So if or when Tesla increases the pack sizes, that should also allow higher charge power at a given State of Charge.
Thanks. I guess it all boils down to charging amps. My understanding is that the pack voltage is 350 nominal, which puts charging amps around 700. The amps are spread more or less evenly over all the cells, and since the Cybertruck will have a larger battery, the actual charging amps per cell will be lower than 2170. So the 250kW rate (700 amps) can be maintained longer for the 4680 since each cell isn't charging as fast as 2170 and therefore doesn't produce as much heat. I think that means charging times will be the same as if the battery were 2170 even though the 4680 will maintain 250kW longer. Does that sound correct?
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