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LR battery charging capacity 73.5 kWh (TeslaFi)

LR battery charging capacity 73.5 kWh (TeslaFi)

Update: using TeslaFi I determined that there is a difference between charging energy to the battery and charging energy used. I am measuring 78.5 kWh charging capacity to the charger but only 73.5 kWh actual battery charging capacity.

After updating to 2019.5.15 and observing a range increase from 307.5 to 314.5 miles on my LR RWD Aug 2018 M3, I decided to make an accurate measurement of the usable (effective) battery size based on the amount of energy needed to charge battery. If someone has good data on the previous size or can run the same measurement pre 2019.5.15 upgrade, then we will know if Tesla unlocked some battery capacity (in addition to any possible efficiency or multiplier increase).

Result: 78.5 kWh battery charging capacity = 7.85 kWh energy into battery / 10.0% SOC change

I charged from exactly 60.0% SOC to exactly 70.0% SOC, I know this because I used Tesla's energy app to make sure I stopped and started at those levels. You cannot just use the main SOC display, resolution is only 1%. Tesla rounds the number so 60% could be as low as 59.5%). For example, when I set the SOC charge target to 90.0% it is typically 89.6% when I measure it using the energy app right after charging.

I know exactly how much energy I put into the battery because I measured the charging power at the battery in 5 min increments (e.g. 240 V * 32 A = 7.68 kW) using Tesla's charging app, and recorded the time to charge from 60.0 to 70.0% using a stopwatch (00:60:25).

I tried to validate this result by measuring accurately the energy used to drive 10% SOC, but I don't have the TeslaFi app and using the energy meter is inaccurate. If someone can do this, i.e. capture kWh used in x.xx kWh resolution to drive 70.0-60.0% that would be awesome. I measured 75 kWh effective usable battery based on using 3.0 kWh to drive 4.0% SOC change, but I think it is not precise, I was eyeballing the SOC using the energy app.

Neomaxizoomdweebie | 13/03/2019

After charging to exactly 70%, take the car for a drive. Measure how much charge is required to get back to 70%. Divide by miles.

beaver | 13/03/2019

@Neo yes I tried that, but I cannot accurately measure the energy (kWh) required to drive the 10.0% SOC down, Tesla's trip feature only gives kWh in whole numbers, and I think they do weird rounding stuff. If I get an app maybe I will have enough resolution.

Bighorn | 13/03/2019

I explained in TexasBob’s thread why replenishment is not the same as extraction. TeslaFi with granularity to tenths of kWh to calculate Wh/RM achieved is ideal. To date 73.2 KWh have been available, but it takes more than that to replenish. Battery capacity is 80.5 though it doesn’t fully charge.

beaver | 13/03/2019

@bighorn perhaps my measurement of 75 kWh discharging (driving) is fairly accurate then, 75.0-73.2 = 1.8 kWh --> * 4.1 miles/ kWh = 7.4 miles range added, which is what I observe (307.5 --> 314.5 miles at 100% SOC).

Bighorn | 13/03/2019

@epostby
It’s easier in Model S because kWhs are in tenths. The whole numbers force you to drive 90% nonstop to get a reasonable figure, which is how I’ve derived it. Bjorn has a video driving the 310 mile range with a brief stop. His data yielded 234 and mine 236 Wh/RM so driving capacity of 72.5 to 73.2 kWh.

As a Model S corollary, usable capacity was 73.7 kWh, but it takes 79.5 kWh to replenish.

Bighorn | 13/03/2019

75 kWh would be a record high, but I think the error bar is too large from such a short drive. If you have tenths granularity, go out and burn at least 30 or 30% SOC and see what you get.

Bighorn | 13/03/2019

20 or 30

hokiegir1 | 13/03/2019

I have a feeling TeslaFi is using formulas to calculate theirs and may need to be updated, but I need more than 1 night to confirm.

1) I had my display set to % this morning. TeslaFi showed the 90% and 284.05 miles upon charging completion, but I think it may have been a bit higher (changed the display this morning and will be charging tonight).
2) Last night's charge was from 48%-90%. TF is noting 31.29kwh added, 34.8 kwh used (line losses).
3) In January, I had one charge from 47-90% that was 32.04 added, 33.4 used and one from 49-90% with 30.44 added, 32.0 used.
4) all of those essentially come out to 74.5+/- a little rounding

beaver | 13/03/2019

I just signed up for TeslaFi, I hope the trip data gives me the kWh and SOC granularity that I need.

beaver | 18/03/2019

@Bighorn I did a longer continuous drive at highway speeds today, I estimate discharge capacity as 72.6 kWh.

Range @ 100% = 314.3 miles (using TeslaFi after night charge)
111.37 miles driven, 118.12 miles range used
231 wH/mile

estimated 100% discharge capacity = 72.6 kWh = (111.37*231)/(118.12/314.3)

It's weird that TeslaFi shows my used kWh as 28.22, but multiplying miles driven * wH/mile gives a higher number (29.67 kWh). I don't understand the difference yet.

roger.klurfeld | 18/03/2019

The battery on the LR Model 3 has always been 78.3 kWh. That is what Tesla reported to the government when the Model 3 was first produced. Tesla chose to round down to 75 kWhs. And the range was always higher than 310 miles.Tesla chose to round dwon to 310 miles in the BMS. The company has now chosen to start the range more accurately.

But not entirely. I just got back from a several hundred mile trip. My battery symbol showed I has 107 miles left. However, when I opened the energy app in the car, it predicted a remaining range of 145 miles. They just use different information to report the remaining range. So which is correct?

beaver | 18/03/2019

@roger.klurfeld it's still not clear to me if Tesla just updated the total range (i.e. multiplier of % SOC), or opened up more battery for usage. It seems not to be on the top-end, so hypothesis is that Tesla is letting users run down the battery more. Yes the EPA range is higher, 332 miles, but that is for a 78.5 kWh battery, Tesla doesn't let us use all of it.

Since my wH/mile average has not changed meaningfully yet I have 7 more miles max range, this leads me to believe I have more battery available for usage. I am trying to confirm this by testing.

Bighorn | 18/03/2019

A bit tired after 2000 miles driving, but your 72.6 kWh matches my original capacity experiment. I think true capacity total is 80.5. I’ve seen CAN data differ from empiric data and can’t explain it, but empiric data is all that matters on a desert highway:) Whether the 234 Wh/RM changes or if you had less available capacity before now or if Tesla did something we’ll have trouble deciphering remains a mystery for a bit longer.

beaver | 18/03/2019

What an epic drive BH, get some rest.

Yes this is still a mystery, if rated wH/mi stays and discharge capacity is not higher (should be 76.1 kwH for 325 mi @ 234 Wh/mi) yet range goes up 5% then where is it coming from? I will keep measuring my drives, as of now it looks like 0% SOC is not the same 0% as before, i.e. we will hit 0% before 0 miles.

CarlEngel | 18/03/2019

I had this same thought after they announced the range increase and before I got the firmware update, so I recorded the data for a direct comparison.

Instead of measuring kWh added for 10% SOC, I did it for 50%+ SOC to reduce rounding errors, and I also tried to take out other factors, like battery temp, for example (heating/cooling the pack uses energy from your charger that doesn't go into your battery). Short story is I found that there's no appreciable capacity difference; my result was 0.5kWh difference total battery capacity, and the repeatability of my method was 0.4 kWh, so no change within measurement error.

beaver | 18/03/2019

@carlengel what capacity did you get for your 50% SOC charge? I got 78.5 and will check again tonight now that I have TeslaFi

czamara | 18/03/2019

78.5 kW battery capacity at 325 miles rated range is 241.5 rated Wh/mile. This matches closely to the rated Wh/mile shown on the energy graph. But there seems to be little agreement on any of this. I wish Tesla would just report the real numbers!

Bighorn | 18/03/2019

@cz
Stop living in your fantasy world. Like a dog with a bone:)

jdcollins5 | 18/03/2019

2019.5.15. I arrived at a Supercharger with 8% (25 miles) remaining. I charged to 100% and displayed 319 miles. It showed 69 kWH and 294 miles added.

If you ratio this 69 kWH/ 0.92 (1.0-0.08). = 75 kWH.

CarlEngel | 18/03/2019

Before range increase (2019.5.4)
41%-->90% SOC: 78.6 kWh total "battery capacity"

After range increase (2019.5.15)
32%-->70% SOC: 78.8 kWh total "battery capacity"
24%-->90% SOC: 79.2 kWh total "battery capacity"

Note I said "battery capacity", since this is based on energy into the car; real battery capacity is slightly lower than this due to charging losses (both charger itself and battery electrochemical losses) and any auxiliary power draw while charging, which will vary with conditions (active battery heating/cooling, HVAC, etc).

Bighorn | 18/03/2019

I’ll repeat myself, but adding energy is different than extracting, as suggested. On the 85 kWh Model S, you add 79.5 kWh to get 73.7 kWh to use to drive. Better to know what you have to use than what it took to fill it up.

JAD | 18/03/2019

Bighorn, are you saying the S85 has about 73.7 kWh usable and the 3LR has 73.2 kWh? So basically the same size usable? That would seem to match my range between my S and 3, I just always thought the S had a 10% bigger battery.

CarlEngel | 18/03/2019

@Bighorn, this is why I said "battery capacity", and included points on charging not being 100% efficient. The point of the test isn't to measure the actual battery capacity, it's to compare before and after the range-increasing firmware update to see if the accessible capacity has been increased. As long as I'm doing the test and measuring things in the same way, the before/after comparison is valid (within the ability to control for external factors).

Bighorn | 19/03/2019

@JAD
My Model S was 265 rated miles times 278 Wh/m or 73.7 kWh and the 3 is 310 rated miles times 234 Wh/m or 72.6 kWh. So essentially the same capacity, but the 3 is more efficient and charges faster. And much faster, soon...

@Carl
My “as suggested” phrase was acknowledging your awareness of the issue. I just never thought that we’d see an increase in absolute top end charging plus it confuses the convention we’ve used for 5 years now. There is validity that the replenishment number would increase if more energy could be extracted from a priorly unavailable buffer, but that wasn’t a common number to derive. In the grand scheme, there’s no bad data, but we really need more folks calculating usable capacity to divine what changed.

beaver | 20/03/2019

Update: using TeslaFi I measured 73.5 kWh charging capacity last night since it took 30 kWh actual energy to the battery to charge from 29 to 90%. This matches the highest diacharge capacity I have measured recently (since the 2019.5.15 update).

beaver | 20/03/2019

Correction : 45.12 kWh added to battery to charge 61%

syclone | 21/03/2019

Is this string the plot for a new episode of Twilight Zone?

beaver | 21/03/2019

@syclone yes how did you know? I can email you the full script. It’s called “don’t charge me bro”

syclone | 21/03/2019

@beaver: I knew it! But, that's OK, I saved the entire episode on 300 8" floppies.