Supercharging: Chill Mode

apacheguy · Jul 28, 2015

As everyone whose experienced SpC very well knows, the taper is the killer. Very rarely is a rate of 100 kW maintained after 45% and after 50% the rate drops like a hot potato. Seeing a lot of variation as to when the taper begins on different cars under different conditions has me thinking as to what the best explanation for this variability is.

I'm pretty certain it all boils down to pack temperature. Some cars cross over 90 kW before 40%, others maintain it to nearly 50%. I guess those who sustain higher current draws later into the charge cycle must have cooler pack temps.

So now to "chill mode." As I'm approaching a SpC, let's say 5 miles out, I'd like to issue a command to pre-chill the battery and redirect cabin resources to the main battery if necessary. My thinking is that this increases the thermal buffer and would thus allow the pack to better handle the initial burst of 90/120 kW supercharging.

Any thoughts? Would this improve SpC measurably? Would anyone like to see chill-mode in a future release?

Electric700 · Jul 28, 2015

It could be worthwhile. I thought the charge rate tapering was due to the threshold cell voltage when approaching a 50% state of charge?

FlasherZ · Jul 28, 2015

In my experience, the crossover point for my car doesn't seem to vary with ambient temperature, I've crossed 90 kW nearly every time between 41-44%, regardless of ambient temperature (35 degF or 100 degF). Even when the wind is roaring across the car with winter temps, it has been consistent.

I would rather see them put a "turbo" button on there when you *need* a fast supercharge, it would push the taper a bit and be aggressive. They could keep track of the use of that button and handle warranty differences based on how you use that button, etc.

apacheguy · Jul 28, 2015

Electric700 said:
It could be worthwhile. I thought the charge rate tapering was due to the threshold cell voltage when approaching a 50% state of charge?

Sort of. But Tesla doesn't go anywhere near approaching those limits. Their taper is very conservative.

FlasherZ said:
In my experience, the crossover point for my car doesn't seem to vary with ambient temperature, I've crossed 90 kW nearly every time between 41-44%, regardless of ambient temperature (35 degF or 100 degF). Even when the wind is roaring across the car with winter temps, it has been consistent.

Has your car always hit the full 120 kW when < 30% right off the bat? Chill mode could also be used to ensure your car is ready to withstand the initial blast instead of having to back off early while the pack conditions itself.

Also, check out these posts of folks getting over 100 kW after 40%:

Drove a lot today, just so I could Supercharge for the 1st time! (geek info inside) (see mobile app screen grab)

Supercharging Taper Curve for D+ Pack (see cosmacelf post 8)

If you are crossing 90 between 41-44%, then that seems to suggest improvements are possible.

Oba · Jul 28, 2015

As should be apparent, when you guys start throwing around data, you might want to specify what the data is for:

90
85A, B, C, D
70
60

FlasherZ · Jul 28, 2015

apacheguy said:
Has your car always hit the full 120 kW when < 30% right off the bat? Chill mode could also be used to ensure your car is ready to withstand the initial blast instead of having to back off early while the pack conditions itself.

Generally, it jumps right to 116-118 kW.

Also, check out these posts of folks getting over 100 kW after 40%:

Supercharging Taper Curve for D+ Pack (see cosmacelf post 8)

See my post #13 in that thread. 104 miles is 39.2%.

Here's my curve from post 13:

15% - 122.9 kW
20% - 122.9 kW
25% - 118.9 kW
30% - 114.9 kW
35% - 104.7 kW
40% - 97.4 kW
45% - 86.8 kW
50% - 78.9 kW
55% - 71.2 kW
60% - 61.7 kW

If you use my curve, at 39% you'll be getting roughly 99 kW, which is close to the 101 kW he shows at that SOC. I'm willing to bet that if we saw his entire curve, it would drop below 90 within another 5% SOC.

- - - Updated - - -

On the other case you have, 108 mi is 40.7%; the screen shot shows 102 kW at that point.

If you take my curve fall-off, you lose an average of 2.1 kW over each %age of SOC between 40-45%. So at 45%, you'd be seeing about 92 kW or so.

I'm using 265 mi as the divisor, it's very possible that his battery pack thinks the voltage is lower than normal so it's allowing a higher rate.

apacheguy · Jul 28, 2015

Good to know. So this seems to indicate that the coolant system has no trouble keeping up with the heat generated from high charging currents. I wonder if the 120 kW cap is removed in the future, Tesla may introduce something similar to chill mode to condition the pack especially on hot days.

whttiger25 · Nov 14, 2016

I've noticed the battery cooling fans seem to only come on after about 5+ mins of charging, presumably after battery has already heated up. Perhaps the moment you plug in the supercharger the cooling systems should immediately turn on full blast, thus the system would be a bit more proactive than reactive.

I believe the cooling systems at max power use a decent amount of energy so it might not be worth forcing them on so early prior to charging, also in general the car shouldn't require a manual step like this to "work".

And just to note my post here isn't in reference to the taper as much as it is a reference to throttling, assuming throttling is due to battery heat and not other factors.

TR5642 · Nov 14, 2016

Oba said:
As should be apparent, when you guys start throwing around data, you might want to specify what the data is for:

90
85A, B, C, D
70
60

Silly question: How to ID 85 submodel? And what differences are there?

apacheguy · Nov 15, 2016

TR5642 said:
Silly question: How to ID 85 submodel? And what differences are there?

Battery revision. Take a pic under the front passenger wheel well facing the battery enclosure.

Nietschy · Nov 17, 2016

The battery needs not to be cold as norway, but in a specific temperature window.
As where I live, it it pretty cold already. 28°F as example: trying to supercharge will start very slow because the car is heating up the battery first before it can take all the oompf from the supercharger. So it starts for about 30kW for a few minutes (SOC is at about 10%) and pulls up as the battery warms up. If at a certain point after this, the BMS realizes that the pack gets to hot, it starts to chill the battery even at 28°C outside.

If I were you, I would forget about this and let the car handle the temperature management.

apacheguy · Nov 17, 2016

Right. There is a lower bound whereby charge rate will be reduced.

However, I've seen the battery run as hot as 44 C while freeway driving in the summer. Chill mode could help bring this down to 30 C and still be within optimal conditions for charging.

No2DinosaurFuel · Nov 17, 2016

I get over 100Kw up until around 60%. I have an S90D. I never seen 120KW though. The most was 112KW.

apacheguy · Nov 17, 2016

No2DinosaurFuel said:
I get over 100Kw up until around 60%. I have an S90D. I never seen 120KW though. The most was 112KW.

Yeah the 90s are different. Can you confirm that you saw this behavior on 8.0? @islandbayy reports that supercharging is much slower with his 90D on 8.0 compared to 7.1

islandbayy · Nov 17, 2016

Firmware 7, original release with car. Max was around 105kW, for only a short time and quick taper.
Firmware 7.xx update during beginning of summer. Supercharging speeds up to 112kW. Could hold 100kW charge rates until ~58-60%
Firmware 8.0, Instant drop in charge rate. MAX rate I can achieve is 100kW. Taper happens earlier (sorry don't remember exact % of taper). To go from ~2% to 80% takes about 15 minutes longer then updated 7.xx firmware. To go from 80% to 100% takes about 20 minutes longer than before. Total about 35 minutes longer to go from ~2% to 100% than previously.

I have Non-Refresh S90D. Almost 20,000 miles.

islandbayy · Nov 17, 2016

Should note. I have NEVER seen 120kW charge rate EVER on any Trim of Tesla Vehicle. My old 60kW First gen 2013 topped out at 115 after firmware updates (Originally 70kW when delivered), all 85's I've seen max was 118 or less. The New Chemistry batteries (Your Autopilot 60's-75's, and 90's-100's) using the Silicone based anode, The most I've seen was 112kW. Considerably slower then first gen batteries. Though, I find/found (Pre Firmware 8.0) that the taper would last longer, which made up the charge time difference.

No2DinosaurFuel · Nov 17, 2016

apacheguy said:
Yeah the 90s are different. Can you confirm that you saw this behavior on 8.0? @islandbayy reports that supercharging is much slower with his 90D on 8.0 compared to 7.1

I don't know about 7.1 because I only charged in CA when 7.1. And we know most if not all CA supercharger have issues.

The number you asked about is on the latest 8.0 update charging in Yuma and casa grande.

apacheguy · Nov 17, 2016

@No2DinosaurFuel thats interesting even more so because I believe you have a pre refresh 90D just like @islandbayy. Doesn't explain the discrepancy he observes.

No2DinosaurFuel · Nov 17, 2016

apacheguy said:
@No2DinosaurFuel thats interesting even more so because I believe you have a pre refresh 90D just like @islandbayy. Doesn't explain the discrepancy he observes.

Yup I have the old fascia s90d. Build around April time frame as far as I can tell.

islandbayy · Nov 17, 2016

My build was Late June early Feb.

Supercharging: Chill Mode

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