Supercharger Charge Rate vs. Time

StatsApp

I wanted to know how charge rate (kW) varies with time as I use a supercharger to charge my car. So, I added a new graph to my app (Stats: https://appsto.re/i6df7y9) to plot Charge Rate vs time or SoC.

Here is an example of the graph:
https://www.dropbox.com/s/qwsg37ibgl2c08k/charge_rate.png?dl=0


Other features of the app:

o A graph that shows miles driven per day/week/month
o A graph that shows stats related to your charging sessions
o A graph that shows your driving efficiency history
o A graph that shows you phantom drain stats per day/week/month and location of each phantom drain
o Set schedule for heat/cool
o Export your stats to a spreadsheet to analyze on your desktop computer
o Sends notification if you arrive somewhere and leave one of the doors or trunk(s) open (which prevents the car to lock itself)
o Send addresses from your iOS device to your car
o Charging reminder notifies you if the car's battery level is low and it is parked at home and it is unplugged

- Use the Widget to do all this without launching any apps:
o check status of all doors
o battery level
o time to complete charge (when charging)

o App reminds you if the battery level is low (user specified) and the car is at home (user specified location) and it's not plugged in. Of course, the feature is optional and can be disabled, if desired.

melburstein_98043376

And the name of your App is: ???

Blastum_455303

name of app from link above

Stats: For Model S/X/3 cars

Bighorn

Taper curve is dependent on battery size.

StatsApp

@ melburstein Name of the app is Stats and the link to App Store is: Stats: https://appsto.re/i6df7y9

StatsApp

@Bighorn I thought charge rate vs. SoC would be independent of the battery size (if SoC is presented as percentage). If you end up using the app, I'd be interested unseeing your graph. The one that I shared is for my Model-S 75.

Bighorn

My 85 has a charge curve that approximates SOC + kW = 125 +/-7
The 100s are closer to 165. Peak kWs are affected by whether you have a 350V or 400V battery.

StatsApp

@Bighorn I often get a non-linear curve where the charge rate increases at the beginning and then decreases almost linearly (e.g., the sample plot that I shared above). I guess it makes sense that higher capacity batteries charge faster.

The maximum charging rate that I have measured so far has been 95kW. When the supercharger station is crowded, the peak can be reduced to ~65kW. What's the actual peak rate that you have seen?

Bighorn

Early on (2013)I saw low 120 kWs but 115 is typical now when I roll in low. I never see a ramp up, always a steady decrease of approx 1:1 kW/SOC. Only exception on a ramp up is a cold soaked battery which might take up to an hour to see any charging action. Your lower numbers suggest a 350V battery or not ever charging at low SOCs ie 10%.

This faster charging is borne out with the faster cross country times we're seeing with bigger batteries and more efficient cars. A 100D can travel about 10% quicker ie average 55MPH vs 50MPH for an 85 over long distances.

StatsApp

@Bighorn If I add SoC and kW, I get ~125 which is as you mentioned above, so it all makes sense now.
Isn't the charge rate also affected by the occupancy of the charging station and especially if another car is charging next to you from the same station?

I almost always see a quick ramp-up in the first 5 minutes. I live in Souther California which is typically warm.

Flash

Maybe you should change the title to “I want people to buy my app so I made up a reason to create a post”

luckyj

When looking at rate vs time/soc, just keep in mind that it's not a static thing. Also keep in mind that simple linear formulas are an approximation and depending on circumstances can be way off.

Not promoting this app, but being able to collect and review the data will help you learn about what's going on. There are several factors that can affect the rate. Your specific battery pack is just one of them. Battery (and ambient) temperature is another. And if the stall has been recently used (warm/hot equipment or wires slows the rate). Or if you're paired with someone else who is charging.

On my P100D with the battery in ideal charging conditions, it will charge at 100+kW (max around 118-120kW) up to about 63%. So that soc range is pretty flat. Then it tapers off non-linearly. 73% is about 73kW. 80% will be about 50kW. 90% will be around 35kW. 95% about 22kW.

As an example about conditions affecting rate, last night I hit the supercharger arriving with 44%. Charging started at 70kW, 5 minutes later went down to 60, then 10 minutes after that up to 90. I never got much above that because at that point the soc was too high. That was all due to the battery being cold, but then warming up with charging + battery heat on.

Bighorn

If you are sharing a supercharger ie same number pedestal, the capacity (either 120 or 135kW) is shared with up to 75% going to the early bird, and adjusting stepwise as the priority stall requires fewer kWs due to their taper. You can also see power reductions in very hot weather as superchargers heat up--changing stalls can circumvent this to some degree.

StatsApp

This @Teslatap article also shows a slight increase at the beginning followed by a nonlinear decrease. Still, the decrease is very close to linear.

https://teslatap.com/articles/supercharger-superguide/#tapered

PCMc

Bighorn - on my MS90D, I do see a little bit of a ramp up in the kW vs. SOC curve if I'm at the very low end of the battery range. It's then pretty flat in the 30-50% SOC range with the taper really kicking in from there based upon the data I log from VisibleTesla. That's where the taper on the 85 packs like yours seems to start a little earlier than what I see on mine.

MaDoTaa - Are you basing your kW plot off the actual kW value being reported over the API or via calculation based upon reported volts and amps? Part of my question is I'm curious if you still get a amp value when on a supercharger. I use VisibleTesla to log and seemed to be a change at some point last year, I think around possibly 8.1 release, where I no longer get amps reported when I'm at a supercharger.

Bighorn

There is a rather brief ramp at arrival, a handshake of sorts--usually going from 0 to about 10kW then it starts again at 0 and steadily climbs to ~114.

StatsApp

@p.c.mcavoy Tesla API used to report both current and power (in addition to voltage), but several months ago, it stopped reporting current. So, the app now reports power as reported by Tesla and computes current by dividing it by voltage.

luckyj

The current API returns charger voltage and power when supercharging. The battery current has been gone for a while like you mentioned. Here's an example output while supercharging with 50.3:

{"response": {"user_charge_enable_request": null, "time_to_full_charge": 0.08, "charge_current_request": 72, "charge_enable_request": true, "charge_to_max_range": true, "charger_phases": null, "battery_heater_on": false, "battery_range": 307.37, "charger_power": 9, "charge_limit_soc": 100, "max_range_charge_counter": 2, "charge_port_latch": "Engaged", "charger_actual_current": 0, "scheduled_charging_pending": false, "fast_charger_brand": "<invalid>", "fast_charger_type": "Tesla", "usable_battery_level": 99, "charge_limit_soc_std": 90, "managed_charging_start_time": null, "battery_level": 99, "charge_energy_added": 53.55, "charge_port_door_open": true, "charger_pilot_current": 72, "timestamp": 1516415522034, "not_enough_power_to_heat": false, "charge_limit_soc_max": 100, "ideal_battery_range": 384.21, "managed_charging_active": false, "conn_charge_cable": "SAE", "charging_state": "Charging", "fast_charger_present": true, "trip_charging": false, "managed_charging_user_canceled": false, "scheduled_charging_start_time": null, "est_battery_range": 208.21, "charge_rate": 156.2, "charger_voltage": 405, "charge_current_request_max": 72, "charge_miles_added_ideal": 216.0, "charge_limit_soc_min": 50, "charge_miles_added_rated": 172.5}}

Tropopause

I saw a youtube video showing 75, 85, 90 and 100 kWh batteries being Supercharged from near empty to 100%. Not sure if all the vehicles had identical firmware updates but one thing I noticed was the fact the 85 kWh battery was the only one in the group that didn't have a measurable ramp-up time to max charging rate. This gave the 85 a considerable head-start over the others that lasted well into the tapering phase.

Tropopause

StatsApp

Are 85 batteries constructed differently? I thought they just have more cells.

dnfh9581_98180084

Nice app. Can it be set to show Miles instead of km?
Also the screen on my iPhone is indecent to your example: yours has an extra icon between Battery and Graphs and doesn't have the Charge line graph displayed (maybe I haven't had it long enough?)
Any thoughts?

StatsApp

@david Thanks for using there app. yes, the app automatically displays in units that you have configured your Tesla to display and it supports mi/km and F/C.

Regarding the missing tab: you guessed it correctly; it will appear after you drive the car for a couple of days (delete and reinstall it after the car is driven if the tab doesn't show up).

You can also contact us directly using the support button in the app (under settings) for faster response (I usually respond within minutes If I'm awake)

PCMc

@MaaDoTaa - "Are 85 batteries constructed differently? I thought they just have more cells."

The packs all use cells which are referred to as 18650 format, but I believe you will find there have been some tweaks to the chemistry over time. That's why Tesla appears to manage charging rates slightly differently between say the 85 vs. 90 vs. 100 packs differently. And yes the different capacity packs use differing number of cells. This link provides some information from teardown done by an owner/master tinkerer if you are interested in more detail on how the packs are actually constructed out of individual cells.

I've not researched your app thoroughly, but I'm curious how often you ping the car and how this influences some of your statistics, such as vampire drain. My initial playing with VisibleTesla led me to quickly conclude that worrying about trying to track vampire drain well required pinging the car frequently to know accurately when trips start, which just creates more vampire drain by preventing the car going to sleep. While tracking vampire drain is an interesting curiosity, I quickly decided not really of much value.

I also find it curious that in the API it seems that Tesla quit reporting current while supercharging, but yet I still see current reported when charging on my NEMA 14-50 at home.

https://electrek.co/2017/01/24/tesla-teardown-100-kwh-battery-pack/

StatsApp

@p.c.mcavoy Thanks for the detailed and informative response related to batteries (as always)

Regarding how frequently pinging the car and its effect on vampire/phantom drain. This was a major concern for me as I didn't want to cause additional battery drain on the car or my phone just to collect some stats.

TL;DR version: The phantom drain remains unchanged (at ~0.1mi/hr) if you have installed Tesla's default app already. The iPhone battery impact is ~1%.

More details:
Apps cannot run in the background indefinitely in iOS (with the exception of some restricted categories - e.g., apps that play audio). iOS kills you app shortly after it is put in the background. You can tell iOS to launch your app in the background periodically. How often iOS will actually launch your app in the background is entirely up to iOS and Apple does not disclose their algorithm and does not guarantee any minimum period for doing so (it is not more frequent than every 20-30 minutes and probably much less frequent). iOS also optimizes battery life by collecting all requests from different apps to be launched in the background and launch them together. This is good for your iPhone and that's why iPhone/iPad battery life is good.

That's how Tesla default app and my app (Stats) work (they request iOS to wake them up in the background and give them a chance to do some work quickly before they get killed). So, in all likelihood, Stats and Tesla app are woken up at or about the same time by iOS and allowed to do their work. This is probably why my measurements show that the phantom drain is the same with and without my app if you have installed Tesla App already.

The other option is to use a server to ping the car and collect information. This makes the app design simple as you don't have to rely on iOS to give you a chance to collect data. This way, you can ping the car as frequently as you want. I tried to avoid this and rely on the iOS background mode only. One exception is the charge rate vs. SoC/time graph which naturally requires periodic measurement. Enabling this increases the frequency of collecting data and increases phantom drain. That's why the collection is disabled by default. I only enable it when I use a supercharger and want to know the charge rate vs. SoC/time. All the other functions of the app are either event-driven or use the default iOS background mode which Tesla app also uses and have virtually no impact of phantom drain rate if you use Tesla app already. I have not tried to measure the impact of Stats without the Tesla app installed because: a) I need the functionalities of Tesla app (e.g., summon, calendar sync) and b) I can live with the ~0.1 mi/hr drain rate with default Tesla app.

Re API not reporting current anymore: My guess is that given that the API provides power and voltage, they figured providing current is redundant. In the app, I report all three (and number of phases of charging)