Max usable Kwh you've seen on TeslaFi

[gilscales]

For me personally, I have never seen 69 Kwh's used on my TeslaFi, I recently made a 249 mile drive starting at what TeslaFi had seen as 100% leaving Harris Ranch but my Tesla app showed 5 min remaining on the charge and approx. 2 miles or more short of what I had seen when leaving my home when I last charged to 100%

I had to keep slowing my speed at the end to get to my destination and about 1/2 Mile before arriving my gauge went to 0 for the first time in over 30k miles on the car, honestly if I thought I was going to cut it this close then I would have stopped for a 10 min charge in Sacramento.

So this is the only drive I have ever made from 100% to 0% and TeslaFi shows 68.24 Kwh's used, how accurate this is I have no idea?

 

[cypho]

It is not accurate. The Wh/Mile shown on telsafi is always very different than what is shown on the trip computer.

Best I can tell teslafi polls the instantaneous power usage once a minute and assumes the previous 59 seconds were the same.

 

[gilscales]

It is not accurate. The Wh/Mile shown on telsafi is always very different than what is shown on the trip computer.

Best I can tell teslafi polls the instantaneous power usage once a minute and assumes the previous 59 seconds were the same.

Damn, I did not even think to look at my trip computer!

 

[AlanSubie4Life]

Damn, I did not even think to look at my trip computer!

The trip computer also reads low (in my opinion).

On a brand new car, battery available energy is ~78kWh. That is for sure because it is from the EPA Tesla-provided discharge event.

If you fully recharge from 0 miles, you’ll add about 76kWh (this is extrapolated from many partial charges). Obviously there is some available energy below 0 miles for a new battery with a BMS and SoC that are all clear on the exact status.

If you fully discharge from 310 to 0, you’ll get about 71.3kWh displayed on the trip meter (this is extrapolated from many partial discharges over a wide range of SoC)

The constants I’m using here are for all trim level AWD Model 3s. It’s ~230Wh/rmi for discharge and 245Wh/rmi for charging.

They are different for the other vehicles. (The LR RWD will end up with similar capacities though.)

So your results look fairly consistent. I have no idea exactly what TeslaFi reports - the above discharge number is from the trip meter.

It looks like they are using a constant of 222Wh/rmi. You have an LR RWD? That pretty much checks out since 325rmi*222Wh/rmi is 72kWh.

 

[darth_vad3r]

Damn, I did not even think to look at my trip computer!

Noooooooooo... this would have been key. Repeat the test!

 

[darth_vad3r]

It is not accurate. The Wh/Mile shown on telsafi is always very different than what is shown on the trip computer.

Best I can tell teslafi polls the instantaneous power usage once a minute and assumes the previous 59 seconds were the same.

It could also just take rated miles used (now minus start) and multiply that by a consumption constant for your trim.

 

[cypho]

Here is a recent drive showing the difference between teslafi and the trip computer.

Trip computer:212 wh/mi
Teslafi: 198 wh/mi

 

[darth_vad3r]

Here is a recent drive showing the difference between teslafi and the trip computer.

Trip computer:212 wh/mi
Teslafi: 198 wh/mi

LR RWD, AWD, or Performance?

 

[cypho]

LR RWD, AWD, or Performance?

AWD

 

[AlanSubie4Life]

Here is a recent drive showing the difference between teslafi and the trip computer.

Trip computer:212 wh/mi
Teslafi: 198 wh/mi

Looks almost like you have an LR RWD with those ridiculous stats...that's insanely good for an AWD at those speeds (65mph average or so). Off-topic: Were you drafting or do you run special tires...maybe just a stiff tailwind???

Yeah, I can't make sense of that. I don't use TeslaFi, I use Stats, and I'm not sure what number/API call TeslaFi is using (someone here could probably explain - or your explanation could be correct).

The trip meter suggests you used 54.16kWh @ 212Wh/mi (255.5mi)

While TeslaFi suggests 50.47kWh @ 198Wh/mi (254.8mi)

At least the division checks out...

Assuming they actually accurately report the rated miles use, though, your trip meter constant is 54.16kWh/229rmi = 236Wh/rmi, which is pretty close to what I would expect (230Wh/rmi), but not quite. It might well be more accurate than my 230Wh/mi number due to the number of sig figs available to you vs. the multiple measurements I have done (which have maxed out at about 100 miles). But honestly I don't quite trust the TeslaFi source, since I've never used it and other data here is apparently way off (as you say, it just may be undersampled).

 

[darth_vad3r]

AWD

@gilscales what about you, RWD, AWD, or Performance?

Using the kWh used divided by rated miles used theory, you two have slightly different ‘constants’ of:
222.4 Wh/mi vs 220.1 Wh/mi

 

[AlanSubie4Life]

ake rated miles used (now minus start) and multiply that by a consumption constant for your trim

It could. But it definitely would have to misidentify the trim in this case. 229.26rmi*220Wh/rmi = 50.4kWh....that would be wrong though. The constant is definitely not that low (at least last time I checked!) for the Performance/AWD.

Or maybe I'm wrong and I need to check my constant again. So much fun.

 

[cypho]

Looks almost like you have an LR RWD with those ridiculous stats...that's insanely good for an AWD at those speeds (65mph average or so). Off-topic: Were you drafting or do you run special tires...maybe just a stiff tailwind???

Aero wheels & factory tires. Pressure a bit higher than normal at 45 cold psi. Cruising on Autopilot the whole drive with distance setting = 7.

 

[AlanSubie4Life]

Aero wheels & factory tires. Pressure a bit higher than normal at 45 cold psi. Cruising on Autopilot the whole drive with distance setting = 7.

Impressive. What software version was this on, and what day was the drive done?

 

[cypho]

Impressive. What software version was this on, and what day was the drive done?

Drive was on August 11, 2019
Software 2019.24.4

 

[AlanSubie4Life]

Drive was on August 11, 2019
Software 2019.24.4

Cool. Looks like you had a fairly consistent general 5-10mph tailwind too. Anyway, end of off-topic. TeslaFi remains a mystery to me.

 

[AlanSubie4Life]

Damn, I did not even think to look at my trip computer!

I too, am very sad that you did not look at this. As suggested, time to repeat the experiment!

 

[animorph]

Also go back in TeslaFI and see how many kWh it took to replace that drive energy. That's a better indicator of battery capacity since rate of discharge affects how much energy is available from the battery.

 

[gilscales]

@gilscales what about you, RWD, AWD, or Performance?

Using the kWh used divided by rated miles used theory, you two have slightly different ‘constants’ of:
222.4 Wh/mi vs 220.1 Wh/mi

RWD LR from 4/18 when it was the only choice available.
I did sacrifice some range with the sport wheels and set of 255/40/19 Conti DWS06 (currently have about 12k miles on them so the range has been improving vs. when they were new.

 

[darth_vad3r]

Also go back in TeslaFI and see how many kWh it took to replace that drive energy.

I don't disagree with this, but...

That's a better indicator of battery capacity since rate of discharge affects how much energy is available from the battery.

Are you sure you aren't thinking about capacity in mAh, not kWh (energy)?

I've seen charts where discharge at 0.1C, 0.2C, 0.5C, 1C all extract different mAh out of a battery, but I thought the kWh you'd end up with would be the same? As long as you are measuring accurately? Maybe that's the issue, you can't measure accuratley due to voltage drops under load?

Hmm, I dunno... the voltage DROPS under higher C rate discharge ... so ... yar, hmm, heat loss in the battery at higher C-rates ... so ya, usable energy delivered by the battery is lower.

Carry on, I think I'm following it all now

@AlanSubie4Life that makes quoting the EPA 'capacities' not necessarily comparable to real-life even at the same average consumption because unless you follow the EPA test cycle exactly, your drive to average X Wh/mi won't have the same discharge profile as the test cycle drive to average X Wh/mi.