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Tesla’s Liquid-Cooled Supercharger Cable – (w/video)
JUL 9 2015 BY MIKE ANTHONY 52
One of many thermal imagery shots of the new liquid cooled Superchargers.
KmanAuto tests out the first liquid-cooled (cable) Tesla Superchargers and provides thermal imagery.
This Supercharger is in Mountain View, California, which is home of the first liquid-cooled version.
It is claimed that these new Superchargers will cut down charging times. If they stay a little cooler than a non-liquid cooled Supercharger, it could theoretically charge a bit quicker, right?
Elon Musk comments that liquid-coiling “also has the potential for increased power of the Supercharger long-term.”
The video below briefly discusses these new Superchargers at the 24-minute mark, at Tesla’s annual stockholder meeting:
Source: ChargedEVs
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52 Comments on "Tesla’s Liquid-Cooled Supercharger Cable – (w/video)"
There is a Supercharger in Mountain View?
Hmm . . . perhaps installed at the Googleplex for the benefit of Google folks? Perhaps Google is paying for the juice.
No, I was wrong. It is at the Computer History Museum. It is a 12 stall Supercharger! Big.
I’m surprised they installed one there . . . it is probably ripe for abuse by a LOT of locals with Model S cars.
But then again, it is right off 101 so it is useful for people traveling on 101.
“It is claimed that these new Superchargers will cut down charging times. If they stay a little cooler than a non-liquid cooled Supercharger, it could theoretically charge a bit quicker, right?”
No. The real limit is in how fast the battery cells can be charged without overheating, not any limitation in the charger. Superchargers can always be upgraded for more current and faster charging by using cables with a larger cross-section, which both reduces resistance and increases the thermal mass; both will reduce any heating of the cables.
Seems to me that liquid cooled cables are probably just a “kewl tech” advertising ploy on the part of Tesla, not anything practical. But I’m not an electrical engineer, so I’m willing to be told I’m wrong here.
If the resistance of the cable increased with an increase in temperature, then cooling would reduce the resistance, allowing more energy to be delivered to the battery.
Whether this is a fact I don’t know either and if the change is significant enough to matter.
I can say that the SC cables do get hot when used so cooling the cables would be helpful. It might also be a that a cooled cable can be used to deliver more energy without getting too hot to the touch.
I wrote:
“…likely that was because the charging cable was using a large number of small wires bundled together.”
Clarification: A large number of small individually insulated wires bundled together. Every charging cable is composed of small wires bundled together, but all the insulation should be on the outside of the cable, not the inside.
“but likely that was because the charging cable was using a large number of small wires bundled together.”
Multiple strand solves the stiff problem to a point but it doesn’t solve the weight problem.
Eventually, as the diameter gets large enough, the outer strands won’t have enough flexibility to handle the bending of the cable either (outer diameter strands have to be stretched/compressed farther during bending).
Using the thinnest cable possible is the best solution to the problem. That would require some kind of cooling. You can always operate copper cable at higher current load if you can manage its temperature. Of course, one can switch to silver cable as well but that would certainly cost a lot more and potentially subject to theft…
Correct. Small strands = higher flex. I don’t know how much the cooling jacket adds to weight/stiffness, but if the cables get too thick that will cause issues. Smaller AWG is the way to go if possible.
Maybe the cable is the weak link in the Supercharger system.
Since MikeG said “I can say that the SC cables do get hot when used…”, it appears you are correct.
No, the cable is _an_ issue. But battery charging speed is limited by state of charge. If it weren’t, you could charge a 90% full battery at 120kW.
Tesla’s aim is 100% electric and to achieve that they need to increase charging speed. To do that without having multiple ports or fat cables they’d need something like this.
“No, the cable is _an_ issue. But battery charging speed is limited by state of charge. If it weren’t, you could charge a 90% full battery at 120kW.”
True, but no improvement to the Supercharger (including the charging cable) will help that situation. The limit to how fast the battery cells can be charged, including the need to reduce charging current as they approach full charge (to prevent overheating within the battery cells), can only be changed by improving the characteristics of the cells themselves.
My guess is since cable is hottest, at ~30 minutes, the taper at that moment may be a cable issue.
I am an electrical engineer and the maths behind it aren’t really hard. You have copper wire with a specific resistance of 1.68 * 10^-8 a length of the cable and the radius. With R=1.68*10^-8*A/l you can work out the resistance and with P=R*I^2 the power loss over the cable. You can try some different numbers, but as far as I tried, even with a 1mm cable the losses of charging with twice the speed of today, are below 1%. The problem is that copper gets very hot, very fast and isolators don’t let a lot of heat out. So if you don’t want to burn the isolation, you need cooling. (For todays charging you need 300Amps)
1% of 120kW is 1.2kW =)
That is about the electric hot plate rating.
That is why heat is the problem even when the loss is very small..
Actually if you want to reduce the heating and can’t increase the cable section you need to increase the voltage. Somehow Tesla will have to increase the 96 cells in a row. They could for instance divide the 74 in parallel to 2 times 37 in parallel and increase the 6 in a row to 12 in a row. Those two actions would fourfold the voltage while still keeping the present voltage possible as well. They would allow that 1670,4 Volt only through automatic special secured contacts under the front of the car using an on bumper supercharger. (Present pack is 16 series of 74 parallel 6 serried cells)
ModernMarvelFan, thank you for your detailed response, and for sharing your knowledge. I learned something today!
Some can charge at 90 KW (85 KWh A battery pack, near 1.06C charge rate)
some can charge at 105 KW (60 KWh with older battery pack, 1.75C charge rate)
some can charge at 111 KW (60 KWh with newer battery pack, 1.85C charge rate)
some can charge at 120 KW (85 KWh B or D battery pack, near 1.41C charge rate)
notice that the 85kWh cars aren’t charging at as high a rate compared to capacity as the 60 kWh are charging.
If the cable were the limiting factor it may be that newer battery packs on the 85 kWh size could handle the higher rate, imagine:
85 kWh at 1.75C is 148.75 KW
85 kWH at 1.85C is 157.25 KW
Since no car has been charging at higher than 120KW rates with the current 135KW superchargers it makes sense that something other than the battery packs was a limiting factor.
oh and btw the S70D has been seen charging just above 111 KW but we aren’t sure if the limit is higher and no one has documented the max charge rate or if it shares the max charge rate of the S60.
Tesla packs have a single letter denoting which version of the pack it is.
http://www.teslarati.com/decoding-tesla-battery-pack-version/
I understand that C was only used for 60kWh and that since that article I linked, they’ve gone to at least E.
“For a smaller battery, you eventually reach the limit due to battery. But for larger battery, the current 120kW is certainly NOT the limit.”
We know that 120 kW is the limit for the Tesla Model S’s 85 kWh battery pack, at least when it passes the 60% charge level, because at that point the charger slows down charging to avoid overheating the batteries. You may be correct to say that when initially charging a mostly-empty 85 kWh battery pack, it could be charge faster than 120 kW.
But as I understand it, it’s not just the size of the pack; another factor is that the individual Panasonic/Tesla cells have a high power rating, which allows the Tesla Model S to be charged so much faster than any other plug-in EV.
Yes, 120kW is the current limit due to the SC system which I am guessing is primarily the cables and connectors.
The 85kWh battery pack can certainly handles more.
You are right about the tappering effect of the battery which applies to all Lithium ion battery pack regardless of size (because it is based on the % of the capacity).
But assuming the battery is close to empty, then the higher capacity battery can potentially handle much higher charging rate than the smaller capacity one up to about 70% and then all of them tappering down.
That is why the difference in charging time various very little (few minutes) on a 60kWh pack between a 50kW, 80kW and 100kW charger.. But on a larger pack such as 85kWh, then the difference between 50kW, 80kW and 100kW would have been much bigger…
If Tesla is aimed at higher capacity packs such as 100kWh, then the need for 150kW or even 200kW SC would be greater. At those rate, the cable would certainly need cooling or becomes much heavier/bulkier/less appealing.
Charging rate must slow at greater SOC to avoid Lithium Plating. Lithium plating occurs more easily in cold temperatures, which is why charging rate can be reduced when the car is too cold. Thermal considerations may also come into play as well.
If anything Tesla uses cells optimised for energy rather than power. That means lower charging rate per unit of capacity (disregarding thermal and cooling considerations) compared to for example, the Chevy Volt.
I thought we already saw this thermal view of the new cable here? Or am I thinking of another website? *confused*
What was the temperature before or on the non-liquid cooled version?
The cable is skinny but it is still somewhat stiff. What is really cool about this has little to do with the supercharging station, it is the Computer History Museum, a must see destination 🙂
What a waste of energy.
Well, fast charging in general waste more energy due to excessive heat build up.
But if time is important, then the added cooling will potentially reduce charging time.
Lower temperature can also potentially reduce resistance.
“but since aluminum isn’t as good a conductor as copper, that would necessitate an even larger, heavier, and stiffer cable… which apparently is already a problem.”
I think aluminum cable is actually lighter than copper cables. I could be wrong.
The main issue with aluminium cables is corrosion and compatibility with other metal connector which can lead to contact or wire lead overheating over time…
Aluminum also expands much more when heated.
That is true which leads to the connection loosening over time…
ModernMarvelFan said:
“I think aluminum cable is actually lighter than copper cables. I could be wrong.”
You’re probably right. I wasn’t thinking about how much lighter aluminum is than copper, by volume. Mea culpa.
Would a white jacket help instead of the black? Would it save energy not having to cool the cable that is baking in the summer sun?
An excellent question. I wonder if Tesla engineers considered that? That change certainly could make a significant difference in some circumstances.
That’s a great KISS solution!
In a very hot location, it might make few degrees of difference, but compared with 120kW of power thru the cables for 30 minutes at a time, it is relatively minor.
Plus, white cable coating get dirty and ugly. Why don’t we make it reflective so it is even cooler? =)
But joking aside, I think it makes little difference relative to the amount of heat generated from the heat within.
Emissivity is what’s important, and black generally has a higher emissivity then white.
+1
Its an unbelievably short run of cable to begin with (only a few feet), so I’d assume the cooling load is also relatively small.
But if they increase the power much more, they’re going to have to start water-cooling that car jack.
Maybe they should put a water cooler on that 14-50 plug that always gets hot.
Wouldn’t it be better just to increase the surface area of the plug’s connection, possibly by moving to tongue-inserted-in-slot instead of pins-inserted-in-holes? If you think about it, the surface areas of all the pins in the plug, taken as a sum total, is pretty small. Significantly increasing that surface area shouldn’t be difficult, even without increasing the size of the charge port.
http://michael.palm-motors.com/wp-content/uploads/2012/09/20120923-142007.jpg
http://evworld.com/press/tesla_ModelS_plugCU480x320.jpg
Hey its their plug, and people seem to be happy with it.
I’ve gone on record 5 years ago that I thought at the time the practical limitation for a production passenger car was a 150 kw charging rate.
It will be interesting to see how soon it is that a manufacturer puts LARGER than a 150 kw charger in a production personal vehicle.
Hey Bill,
Why do you think 150kW is the limit? Is that because of the infrastructure (grid backbone) issue or the connection port issue?
If Tesla can run cooling loop pretty close to the connectors, then I would think the connectors should be able to handle the heat generated at the contact surface since copper is actually a very good heat conductor.
This whole thing reminds me of the Desktops from 15 years ago that clocked the Processor at Ludicrous speeds and got away with it by freezing the chip with a freon refrigerator compressor in the base of the Desktop!
Hey if it works, why not?
Tesla obviously isn’t too worried about the electric bill.
It is hard to get large surface to mate with large surface in connection. Even for the typical blade surface, the designer always remember to make sure the contact surface is tight and “lightly scratched” each time they are mated.
The pressure and anti-corrosion is almost just as important as contact area. Going gold plating would help with the corrosion. To keep pressure and contact surface even and more consistent is slightly harder…
Okay, but surely this is an engineering problem which has been thoroughly addressed thru long experience. It’s not like Tesla needs to reinvent the wheel here. We’re not even talking about high voltage power systems, and surely even those have connections which need to be plugged in and unplugged on a regular basis.
Also, it wouldn’t be the end of the world if, in a future model, Tesla had to abandon the small charge port hidden behind a corner of the tail light, moving to a larger port more like a gasmobile’s gas filling hatch.
* * * * *
I am not endorsing the company, but the website below shows some commercial “high current connectors”:
http://marechal.com/en/industrial-plugs-socket-outlets-and-boxes/article/high-current
“We’re not even talking about high voltage power systems, and surely even those have connections which need to be plugged in and unplugged on a regular basis.”
Actually, not too many consumer electronics or frequently used things have that much higher current rating. Breakers can do that, but we are talking about hundreds of amps here which requires a good contact surface and you are potentially using them daily in an “uncontrolled” environment. The issue is actually harder than it seems.
It is doable, but certainly would be more costly…
Why is there so much speculation that the cable is reason the cooling is needed. A supercharger has 480VAC input and DC ouput. To do this, you need a power supply that transforms and rectifies the input power. It seems pretty obvious to me that the cooling is to protect the electronics inside the supercharger. This is the equivalent of worrying how hot your ethernet cable on your computer is getting; meanwhile you have an overclocked CPU inside.
The actual supercharger is not in the stall seen in the video, it is a large monolith with radiators and fans located in the immediate vicinity with the step-down transformer and fenced off.
The supercharger has its own cooling system.
But the reason the liquid cooling is extended to the cable is for cable cooling and somewhat connector cooling as well.
A supercharger is composed of usually 12 (they’ve apparently made a few with 9 or 6) car chargers – the allegedly ’10 kw’ jobs.
They all run on anywhere from a nominal 220 – 277 volts 50 or 60 hz.
I would like to look at a Canadian supercharger station since that voltage range in Canada isn’t instantly available.
Of course, a transformer could do it (that’s the way all the Lowe’s Stores are handled in canada), or else small buck transformers bringing the Canadian Juice within range.
But the point is, none of the superchargers’ ‘chargers’ run on 480.
Its rather like none of the light bulbs in a commercial building are 208, unless youre talking about the huge quartz things outside. Or, none of the level 1 or level 2 car EVSE’s are 480.