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What's my REAL usable battery?

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andaconda

andaconda

Active Member
Apr 3, 2021
1,118
739
S.W. Montana
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#1
OK, figure this out for me.
Model Y long range AWD -March 2021 build.
Live in SW Montana - lots of hills, and you need to drive the interstates at least 80~85 to keep from getting run over.
Charged to 100 percent -- drove 234 miles, down to 9 percent.
64 KW used during drive. Nagged me to plug it in when I got to 8 percent - so I did. I've never ran it below 5 percent.
So is my usable battery about 70 KW? I switched from miles to percentage to relieve my range anxiety.
 
#2
We all seem to switch from miles to %. It woks better.
Running about 70 mph seems to require about 20 kW. 75 kWh / 20 kW = 3.75 hours (units are important)
3.75 h X 70 mph = 263 miles.
You said you ran the battery to 9% and went 234 miles. Ao 100% / 91% = about 1.1 and 1.1 * 234 miles = about 260 miles.
So I'd say that's about right. An ICE drivetrain efficiency varies a lot with speed. It generally gets more efficient at higher speeds. An EV drivetrain has a much more constant efficiency so at higher speeds the range decreases due mostly to drag.

You can ride your bike all day at 10 mph. Probably 50 miles or so at 13 mph. Not very far at 20 mph unless you're in really good shape. You probably can't even reach 30. All due to drag.
 
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#3
Feathermerchan said:
We all seem to switch from miles to %. It woks better.
Running about 70 mph seems to require about 20 kW. 75 kWh / 20 kW = 3.75 hours (units are important)
3.75 h X 70 mph = 263 miles.
You said you ran the battery to 9% and went 234 miles. Ao 100% / 91% = about 1.1 and 1.1 * 234 miles = about 260 miles.
So I'd say that's about right. An ICE drivetrain efficiency varies a lot with speed. It generally gets more efficient at higher speeds. An EV drivetrain has a much more constant efficiency so at higher speeds the range decreases due mostly to drag.

You can ride your bike all day at 10 mph. Probably 50 miles or so at 13 mph. Not very far at 20 mph unless you're in really good shape. You probably can't even reach 30. All due to drag.
Click to expand...
So how many KW can I expect from my battery. I don't care so much as to the miles.
 
#5
Anaconda - "So how many KW can I expect from my battery. I don't care so much as to the miles."

I think you mean kWh. Think of kW as HP (power). 0.746kW = 1HP
Think of kWh as gallons of gasoline (energy) a gallon of gas = about 36 kWh.

Your battery has about 75 kWh of capacity when new. It declines as the battery is cycled. How much depends on a lot of factors.
There is a lot of info about this on the interweb. There are expectations your Tesla battery will last 300,000 miles or so.

evannex.com

How Long Will My Tesla Battery Last? - Updated

If you’re looking to buy an electric vehicle, or already own one, you probably have concerns over battery life. You want to know, how long is my battery going to last? It’s true that over time batteries can fail, or lose capacity from mileage or age. There are other factors, like extreme heat...
evannex.com
 
#6
Except that the pack gross capacity has changed over time, there have been 75, 78 and 82kWh packs. There is a bottom buffer of 3-4kWh that is subtracted when computing the remaining percentage or miles, but you can use it while driving past 0%... So it depends on which battery is in your particular car. There are people that have tried to graph that out...it's always difficult to tell.
Without knowing better, you can expect somewhere between 75 and 82kWh gross capacity. They typically degrade a few (5?) percent in the first year and then really slow afterwards... so maybe after a year it would be between 72 and 78? Newer batteries might degrade at a different rate though. Again, hard to tell precisely.
 
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#7
So I could have gotten at least 6 more kWH out of it? Basically, I need to know if I charge to 100 percent, can I make it home? Yes, I do use ABRP - and it tells me to go out of my way to charge. ABRP is conservative and the Tesla trip planner is a little over optimistic so I split the difference.

FWIW - I'm still trying to get over a little range anxiety. One of my trips take me 101 miles, but the nearest supercharger is 20 miles out of my way in the wrong direction, and it limits all charges to 80 percent - which makes it a poor choice -- 4 chargers for a county of 100,000. And I have pulled in there with 2 of the 4 chargers inoperable.
 
#8
I suggest that you stop worrying about how many kWh you have. Range is influenced by so many factors, that you can enter in ABetterRoutePlanner to get a great estimate. Play with abrp to see how different routes would play. Adjust settings like speed and wind to understand how they affect consumption. It's a tool, don't be afraid to simulate trips. That plus a few trips will reduce anxiety.

If you find abrp conservative, it's either because you feed it bad parameters or you do not drive in the conditions you gave it. It is otherwise fairly accurate. A handful of percent points is very precise.
I found the tesla planner optimistic because i drive over the limit, it doesn't know about wind etc. Abrp is your friend.
 
#9
Oh, and about anxiety and charging. There are options. There are probably level 2 chargers where you're going? You can plug there and gain a few percent, wait longer if you have to. Worst case a 120V plug works and there are billions of those everywhere. Do not just think of superchargers. Maybe abrp won't tell you but you know...
I'm saying you won't be stranded unless you do it on purpose. It might simply be slower than you'd want.
 
#11
The easiest way to estimate your battery size is by using the data on your energy screen and the current SOC%.
(Wh/mi*estimated remaining range)/SOC%. For example I currently am at 79% SOC with usage of 235 wh/mi and 247m estimated range left
So (235*247)/0.79 = 73.5 KWh. I have a Feb 2021 MY so I assume I have a 78 Kwh battery pack and the range estimate holds approximately
(78000-73500)/235 = 19 miles of emergency range in reserve.
 
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#12
Geech72 said:
The easiest way to estimate your battery size is by using the data on your energy screen and the current SOC%.
(Wh/mi*estimated remaining range)/SOC%. For example I currently am at 79% SOC with usage of 235 wh/mi and 247m estimated range left
So (235*247)/0.79 = 73.5 KWh. I have a Feb 2021 MY so I assume I have a 78 Kwh battery pack and the range estimate holds approximately
(78000-73500)/235 = 19 miles of emergency range in reserve.
Click to expand...
However, I would not recommend testing that reserve range hypothesis in the real world
 
#15
andaconda said:
So I could have gotten at least 6 more kWH out of it? Basically, I need to know if I charge to 100 percent, can I make it home? Yes, I do use ABRP - and it tells me to go out of my way to charge. ABRP is conservative and the Tesla trip planner is a little over optimistic so I split the difference.

FWIW - I'm still trying to get over a little range anxiety. One of my trips take me 101 miles, but the nearest supercharger is 20 miles out of my way in the wrong direction, and it limits all charges to 80 percent - which makes it a poor choice -- 4 chargers for a county of 100,000. And I have pulled in there with 2 of the 4 chargers inoperable.
Click to expand...
It only limits you if you don’t do anything. Plug in, once charging starts move the slider over to 90 or 100.
 
#17
andaconda said:
OK, figure this out for me.
Model Y long range AWD -March 2021 build.
Live in SW Montana - lots of hills, and you need to drive the interstates at least 80~85 to keep from getting run over.
Charged to 100 percent -- drove 234 miles, down to 9 percent.
64 KW used during drive. Nagged me to plug it in when I got to 8 percent - so I did. I've never ran it below 5 percent.
So is my usable battery about 70 KW? I switched from miles to percentage to relieve my range anxiety.
Click to expand...

Calculate the capacity yourself:

teslamotorsclub.com

Calculating Your Battery's Estimated Capacity Using the Car's Energy Screen

Re posting here and making this a sticky post so it doesnt get lost. @AlanSubie4Life originally posted: =========================================== (originally posted by @AlanSubie4Life. Original thread this appeared in can be found here: ( 2021 model Y scan my Tesla battery size)...
teslamotorsclub.com teslamotorsclub.com
 
#18
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