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How pairing at Supercharging works
- Thread starter David99
- Start date
suwaneedad
Member
Anyone have insight into this?
Situation: Tifton GA today is full, (7of8, 1 being broken), and upon plugging in (22%SOC) I immediately got 48kw. Within two minutes I was at 51kw where it has held steady for the duration of the SC event (ended at 80%SOC).
If I've followed OP correctly, the paired car was drawing in the neighborhood of 84kw since I was not receiving more than 60kw (but was receiving more than 48kw). I think this all implies that for some reason my car wasn't able to receive 60kw. Seems like it's either that, or perhaps the overall SC location was overdrawn, or the chargers were overworked today and too hot to provide full 144kw between the two paired vehicles? It's odd (to me) since based on OP I'd have expected to receive a multiple of 12kw...48 or 60 presumably since I was obtaining 51kw. And it is 50 degrees and cloudy today, so my pack shouldn't be anywhere near as hot as it has been in the summertime when I've used this same SC location (yet it was empty in the summertime weekday visits), so I don't see my pack being a limitation here.
Help?
When a site is full (or close to full) the power is often reduced. I have seen this many times. When I add up the power between my car and the other car on the other paired stall it doesn't add up to 120 kW. Often not even close. I believe the total power a site is able to deliver is lower than the theoretical maximum. For example a site with 8 stalls would be able to deliver 120 kW x 4 = 480 kW. In reality it often cannot. So when a site is getting full some cars will get less than they could take. But of course there is always the odd situation where a car decides it can only charge at a limited rate for no apparent reason. I have seen this several times when I was the only one at a site and still got less than the normal speed.
Today I had a warmed X P100D battery at 1% SOC, supercharging at the oldest supercharger in Japan. It went to 30kW with AC off. I was paired and I was second. Then after 10% the power went up to 90kW.
This seems to suggest that:
- in this specific case, the first car was over 80% and drawing minimum power when my car reached 10% SOC
- Old superchargers seem to have 10kW x 12 stack, rather than 12kW x 12 stack.
Can we ask Tesla to upgrade to new chargers?
This seems to suggest that:
- in this specific case, the first car was over 80% and drawing minimum power when my car reached 10% SOC
- Old superchargers seem to have 10kW x 12 stack, rather than 12kW x 12 stack.
Can we ask Tesla to upgrade to new chargers?
No, what it suggests (and is consistent with other reports) is that supercharging is slower at very low states of charge, until you get up to 10%.Today I had a warmed X P100D battery at 1% SOC, supercharging at the oldest supercharger in Japan. It went to 30kW with AC off. I was paired and I was second. Then after 10% the power went up to 90kW.
This seems to suggest that:
- in this specific case, the first car was over 80% and drawing minimum power when my car reached 10% SOC
- Old superchargers seem to have 10kW x 12 stack, rather than 12kW x 12 stack.
Can we ask Tesla to upgrade to new chargers?
Yes, that is a behavior that has been observed for quite a while in the newer types of batteries. The battery chemistry Tesla used to use in the really old 60kWh and 85kWh battery packs, like up until about 2014-2015 was a bit different. It was like the lower the better, and the fastest charge rate was from low single digit %. Since the 90 and 100 packs, they do have that different behavior, where they stay cautiously slow up to 10%-ish before ramping up fast.
Yeah I know - my bad. I meant they happened at the same time; under 10% and the other car being up 80%. If the other car was pulling more power, my power after 10% wouldn't be 90kW.
A pair of stalls under perfect conditions should deliver ~145kW between the two. The problem is as we all know, it's never perfect conditions outside of commissioning day maybe.
For urban's this is split evenly. For older style V2 superchargers this is dynamic with a max of 120kW to one car, and leftover power to the second car. (V1 superchargers were limited to 90kW, but they have all been replaced at this point I think at least in North America.)
Factors that influence the pairs can be any of, or any combination of the following: Car battery state of charge, car battery temp, car battery wear, "outside the site" power supply issues, failed chargers inside the supercharger stack (remember they have 12 per pair and continue to work with reduced output if individual ones fail), poor connection at the charge port, charger handle wear, charger handle hot from previous use, a sensor failure in the handle, wear in the wiring between the handle and the pedestal, battery revision, some wiring issue between the pedestal and the main cabinets, overall cabinets overheating from fan failure, car just asking for less power then it can actually take for some reason due to software issues, & probably some other things I can't think of at the moment.
The point is, it's almost impossible for those of us who aren't Tesla supercharger technicians with proper testing equipment to figure out one of these possible issues, much less multiple failures/degradation points happening at the same time. There's billions of possible combinations of factors that can influence charging speeds. I wish it was a simple diagnosis, but it's just not.
This might be at certain sites, but I've had the fortune of plugging in with under 5% SoC, and then having another person plug in immediately next to me and pairing the stalls, also under 15%. We added up the power output and it was close to 142kW between our cars. So maybe some locations might be limited to 135, but I've personally seen 145kW. This was at Barstow, CA in Nov of 2017. Also I should add I was getting ~110kW as first to plug in, and the second car was only getting ~30kW.
/edit. I should add my paired stall story from above was before the software change that slowed down supercharging when you are at very low states of charge. I've noticed this personally as well, where you do not get fast charge rates when under ~5% SoC but once you go past a certain threshold it will jump up in charge rate, regardless of being paired or not.
My previous was a P85+, and I did notice the change in supercharging speeds when at very low (under 5%) states of charge. They changed that power delivery curve for everyone I believe, not just for specific packs.
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A couple of refinements:
It's very close to that. It's not just leftovers to the secondary car. They do have it set so the secondary car will get at least 30kW minimum. So in certain circumstances that can reduce the primary car's speed just a little.
Yes, all of the 90kW ones have been upgraded.
All of the new ones being put in are the 145kW type. But there are still many of the older ones that are still 120kW and 135kW.
gnuarm
Model X 100 with 72 amp chargers
I see this as a problem with Tesla charging which is similar to learning about the car as well, not enough information. I don't care if there is a ton of info in the user guide, there should be context information available for everything on the user interface and in this case the charging interface should explain why you are getting this rate. Is the limitation the charger? Is it that you are the "other" car on the pair? Is it that your battery is cold and this is as fast as it will charge until it warms? Etc.
I think a small percentage of owners read anything here or online in general. It's a car. People don't expect to need to study at Tesla U. to learn how to charge it. Most people have no idea that the battery cares about temperature and have no idea that every charger is not independent. I think out of the couple of dozen people I've met at chargers only one or two knew that the highway chargers are paired and the charging implication of that.
gnuarm
Model X 100 with 72 amp chargers
I think your analysis is flawed. If the charging is done by 12 kW units as the OP stated, then the paired car may be charging at 73 kW which than must use 7 of the available 12 chargers, wasting 11 kW.
TexasEV says, "Superchargers have max output of 135 kW" which is 9 kW shy of the 144 kW others have said. I don't know where this comes from and I can't see a particular reason for it. But if true, it would be a noticeable limitation.
I do rather doubt they limit the total site power. I can't see a reason to do that. I expect they designed the installation to work with 100% load given the already noted limitation of pairs. Adding a further limit to the site would make for more complication of the design and provide little in the way of utility. Sites can have 6, 8, 10, 12 and 16 chargers that I have seen. Given that they size the number of chargers for the expected use, it doesn't make sense they would add a limitation to the overall site that would further reduce the average charging limit per car when most heavily used. I hope they wouldn't be that limited in their vision.
gnuarm
Model X 100 with 72 amp chargers
Today I had a warmed X P100D battery at 1% SOC, supercharging at the oldest supercharger in Japan. It went to 30kW with AC off. I was paired and I was second. Then after 10% the power went up to 90kW.
This seems to suggest that:
- in this specific case, the first car was over 80% and drawing minimum power when my car reached 10% SOC
- Old superchargers seem to have 10kW x 12 stack, rather than 12kW x 12 stack.
Can we ask Tesla to upgrade to new chargers?
I know at 1% (well, 2% actually) the charge rate is limited because of the state of charge. I don't know the number at which it reaches max charge rate, but it is not below 5% I seem to recall.
To go from a 30 kW charge rate to 90 kW in one jump says to me the other car charging rate was high and then ended. If the charging rate was limited by your battery SoC I believe it should have gone up in very small steps as your SoC increases. I've seen this before on my car.
It is 72 kW, not 73. 72 / 12 = 6.
Supercharger sites are fed by 3 phase power. Three chargers always act as a group to ensure all three phases are used equally. the max total of 144 kW comes from 4 groups (of each 3 chargers). 4 x 3 x 12 kW = 144 kW. 120 is the maximum per stall probably limited by switches / wire / breaker size. Urban chargers are 72 kW per stall. Again, two stalls are fed from one cabinet so the total is 144 kW.
It's sometimes the limitations found at a specific site and a matter of cost to avoid hefty peak demand charges. As mentioned, it is much better to divide the total power up to more stalls. 12 car charging at a slightly reduced rate is better than 8 car charging and 4 waiting in line getting frustrated and posting about it on social media. It is much preferable to be able to plug in and getting a coffee rather than having to wait in line. Even when all stalls are in use, there is a chance all of them combined are not reaching the max power. Two cars at a pair could be at a high SoC and thus not use the full power available. By having more stalls this extra power could charge more cars even if they are not getting the full power they could take. Also keep in mind, if you wait in line and then charge faster, you spend just as much time overall, than when you plug in and charge at a slower rate. Except it is much better to be able to plug in and do other things.
I wonder if V3 superchargers will not just feature updated power output, but also updated pairing... Perhaps even beyond just pairs.
Double, triple, perhaps even 4 times the output, but at the same time also the power is split amongst 4, 6 maybe even 8 pedestals. Similar to what we have now but on steroids.
Pretend 4 cars all with low SoC plug into a "new" 8 stall octo-group served by one new 576kW max V3 cabinet. Those 4 are "classic" supercharger enabled vehicles and each start sucking up 120kW max happily. (So there's 480kW taken up).
Then a new Roadster 2020 shows up with its fancy V3 enabled supercharging, and it plugs in (low SoC also). At this point there's only 96kW left over, so the roadster owner grumbles but goes to get coffee. The thing is, the OG supercharging cars are now rapidly starting to taper, so they all drop down to 60kW range, and suddenly there's ~280kW extra now available to get dumped into the Roadster, so it ramps up quickly and everyone is happy.
Even in California where entire sites are frequently full, there's still plenty of power to go around if it's split 8 ways. 8 cars plugged in will all be at different taper points, so dynamic load shifting will be much smoother when compared to just the simple pairing we have now.
In fact, I bet the Megachargers for the Semi program will probably just use the same V3 cabinets, but configured to output a ton of power to only 1 or 2 megacharger pedestals for big trucks. Converting those for use at car supercharger sites (like I mentioned above) would be pretty simple (pump power dynamically to 8 cars, vs 2 trucks). The only potential downside is that this brings up the possibility that if there's a failure at that one V3 cabinet, a large chunk of pedestals will go down vs the current setup where we only lose a pair.
Double, triple, perhaps even 4 times the output, but at the same time also the power is split amongst 4, 6 maybe even 8 pedestals. Similar to what we have now but on steroids.
Pretend 4 cars all with low SoC plug into a "new" 8 stall octo-group served by one new 576kW max V3 cabinet. Those 4 are "classic" supercharger enabled vehicles and each start sucking up 120kW max happily. (So there's 480kW taken up).
Then a new Roadster 2020 shows up with its fancy V3 enabled supercharging, and it plugs in (low SoC also). At this point there's only 96kW left over, so the roadster owner grumbles but goes to get coffee. The thing is, the OG supercharging cars are now rapidly starting to taper, so they all drop down to 60kW range, and suddenly there's ~280kW extra now available to get dumped into the Roadster, so it ramps up quickly and everyone is happy.
Even in California where entire sites are frequently full, there's still plenty of power to go around if it's split 8 ways. 8 cars plugged in will all be at different taper points, so dynamic load shifting will be much smoother when compared to just the simple pairing we have now.
In fact, I bet the Megachargers for the Semi program will probably just use the same V3 cabinets, but configured to output a ton of power to only 1 or 2 megacharger pedestals for big trucks. Converting those for use at car supercharger sites (like I mentioned above) would be pretty simple (pump power dynamically to 8 cars, vs 2 trucks). The only potential downside is that this brings up the possibility that if there's a failure at that one V3 cabinet, a large chunk of pedestals will go down vs the current setup where we only lose a pair.
I don't know how expensive those switches are compared to just adding more chargers. Tesla came up with a reasonable compromise between cost and available charge rate. Pairing made sense in the early days when the battery packs would taper down quickly. My old 85 only accepts 58 kW at 50% SoC. Today is different. A Model 3 or S/X 100 charges at around 100 kW up to 70%. There just isn't much power left the entire time a Model 3 or S/X 100 charges on the other side of the pair. Ideally a supercharger site would have all stalls connected to one big charger that can divert to all stalls individually. Every car would get the maximum rate all the way up to the limit of the site. It would not matter where you pull in. I guess that would be a wiring nightmare, though.
As for upgrading existing sites. From what I have learned, the wires from the cabinets to the actual stalls are pretty much at their limit. They are not able to sustain much more power, especially not over a longer period of time. Those are down in the concrete so they would be very difficult to upgrade. The only way to get significantly more power is higher voltage. That would require a new pack. Maybe with the Model Y and Model S refresh it will come. I believe the Tesla plug is also at the limit of what it can handle in terms of Ampere. So again, only higher voltage would enable a higher rate.
As for upgrading existing sites. From what I have learned, the wires from the cabinets to the actual stalls are pretty much at their limit. They are not able to sustain much more power, especially not over a longer period of time. Those are down in the concrete so they would be very difficult to upgrade. The only way to get significantly more power is higher voltage. That would require a new pack. Maybe with the Model Y and Model S refresh it will come. I believe the Tesla plug is also at the limit of what it can handle in terms of Ampere. So again, only higher voltage would enable a higher rate.
On the higher power front perhaps this is where CCS comes into play. I agree a larger power source and smarter routing would help a lot often. Instead of the chunk system we have now (see post 1) instead provide actual dynamic power, a more even spit when multiple cars plug in. Although that would suck for car 1 as it would drop down, but would be helpful for car 2 as it wouldn't be stuck waiting on car 1's taper.
On the contrary, other owners will love you for occupying those less favorable stalls. Please keep up the good work.
HankLloydRight
No Roads
You were only frustrating yourself. If you pull into a paired stall, plugging in won't affect the other car that was there first. You'll only be limiting your charge rate.
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