Why aren’t our Model 3s Supercharging faster?

[Yonki]

Was monitoring my Supercharging today. Started at 120kW as expected. A while later I noticed that it had dropped to 60kW by the time it had 150 miles of range. “That’s normal”, I thought, “Superchargers taper off as the battery gets full.” And I started wishing we would get V3 Superchargers soon, since we’ve all heard that the TM3’s new battery chemistry allows for faster charging.

Then I thought: if the TM3 can charge faster than the S or X, why is the current still tapering off so early? Yes, we can't supercharge faster than 120kW near 0 miles, but surely our batteries could continue charging at 120kW longer.

Please discuss.

 

[Kardax]

Even with 500 kw superchargers, it's still limited by the battery's ability to absorb the charge, so it will follow the same tapering off slope. This is probably why Tesla hasn't been in a big hurry to update the chargers... the upgrade would only be apparent at the very start of charging for a couple minutes at most.

Higher battery pack voltages (800+) would enable faster charging at the same amps (so same cable thickness), but I think Tesla is still using ~400 volt battery packs.

Bigger batteries (Semi/next-gen Roadster) have more cells to absorb more power, so you'll get proportionally higher KW there, but overall full recharge time would be the same as Model 3 if the voltage is the same.

 

[Kardax]

Follow-up: my previous post assumes Tesla continues to use a similar battery tech going forward. There are other battery chemistries available today that able to receive or release power at higher rates, but they sacrifice capacity to get there. Tesla has always strongly emphasized energy density in their packs, and achieve the needed power output simply by using larger packs, which is why their cars with bigger batteries accelerate faster than ones with smaller ones despite the added weight.

 

[GregRF]

source

 

[Nocturnal]

Was monitoring my Supercharging today. Started at 120kW as expected. A while later I noticed that it had dropped to 60kW by the time it had 150 miles of range. “That’s normal”, I thought, “Superchargers taper off as the battery gets full.” And I started wishing we would get V3 Superchargers soon, since we’ve all heard that the TM3’s new battery chemistry allows for faster charging.

Then I thought: if the TM3 can charge faster than the S or X, why is the current still tapering off so early? Yes, we can't supercharge faster than 120kW near 0 miles, but surely our batteries could continue charging at 120kW longer.

Please discuss.

I feel like I see the big slowdown at maybe 70% SoC or so.

 

[ewoodrick]

Why can't it charge faster? That's because the batteries can't handle it. Same as the battery in your phone and every other rechargeable battery. Charge rates will roll off as battery voltage increases.

It's physics.

 

[David99]

I don't understand the dismissive comments towards Yonki. He said the charge rate dropped to 60 kW at 150 miles. That's 45% state of charge. At 45% the Model 3 should still charge at much higher rate than 60 kW. I think his point and concern is valid.

 

[garrett5688]

Not all superchargers are equal - try different stall, or different location. Get more data.

 

[Lloyd]

Normal for 3 IMO

 

[David99]

Normal for 3 IMO

Look at the graph that was posted a few messages up. At 45% a Model 3 should charge at well over 100 kW.

 

[EVDRVN]

The other day I plugged in at 60% and could only get 30kw. Seems pretty darn slow even for a M3 pack. No shared stalls no other conditions to impact the pack.

 

[Matt L]

Seems fine to me

 

[Yonki]

OK, so my initial query wasn't as clear as I wanted it to be (I was on my phone). A picture is worth 1000 words, so:

Since I'd read that the Model 3's 2170s could safely charge at higher rates, I was thinking that maybe the superchargers might just be using a "standard" S & X current curve, in which case it would be possible to extend the 120kW period for the 2170s and charge faster overall (2). Thanks to the plot and link that GregRF posted, it's very clear that the supercharger curve is different (and presumably optimized) for each different battery pack. Also, I now see that since the Model 3 has a lower kWh/mile than the S and X (and therefore fewer parallel cells for similar ranges), at 120kW the current into each 2170 cell would be more than the current into each 18650 in an S or X pack. So what I was suggesting (charging the 2170s at a higher current than the 18650s) is already being done. (Not surprising - Tesla's hardware design is rarely less than stellar.)

So when we talk about faster charging with the V3 Supercharger, it will only be at the beginning of the curve, as Kardax pointed out above and I tried to illustrate in (3).

Appreciate the feedback from all the people that were able to use their words (vs the significantly less helpful disagree button).

(Made a few edits for clarification)

 

[dhrivnak]

I hear the stalls are paired. So if you are on 2A and someone plugs into 2B then the two of you share 130 kWh. So if someone pulled beside you that could easily explain it. Personally I have been impressed with how fast mine charges. 45 minutes will take me from nearly empty to nearly full.

 

[Kermee]

Was monitoring my Supercharging today. Started at 120kW as expected. A while later I noticed that it had dropped to 60kW by the time it had 150 miles of range.

It tapered much faster than I would expect. Charging speed is handled by the BMS and it sounds like the BMS halved your charging rate much sooner. Next time this happens, reach out to Tesla to pull the logs to see why.

The old threads over the summer have floated away from recent memory here on TMC, but Tesla did admit that SC rates "may" be reduced on the Model 3 after many successive SC's within a short period of time. They never gave concrete information on when the BMS would determine this would occur.

Other than someone else showing up and charging on your paired stall, not sure what would cause your charging rate to drop to 60kW at around 50% SoC when you were at 120kW earlier.

 

[Candleflame]

Even with 500 kw superchargers, it's still limited by the battery's ability to absorb the charge, so it will follow the same tapering off slope. This is probably why Tesla hasn't been in a big hurry to update the chargers... the upgrade would only be apparent at the very start of charging for a couple minutes at most.

Higher battery pack voltages (800+) would enable faster charging at the same amps (so same cable thickness), but I think Tesla is still using ~400 volt battery packs.

Bigger batteries (Semi/next-gen Roadster) have more cells to absorb more power, so you'll get proportionally higher KW there, but overall full recharge time would be the same as Model 3 if the voltage is the same.

even with 800V you are still limited by how many Cs the batteries can take. The whole dabate on 800V vs 400V batteries only becomes relevant once you have batteries above 100kwh.

At the moment the biggest issue is the taper.