CyberBeast Battery size Can’t be 122KWH

[cybercricket]

Also another thing... do we know how the energy tracker works ? Is it really total energy used per mile traveled, or is it energy used in the traction subsystem only ? In other words if you sit in a parking lot with AC on for an hour, does it count it towards the current trip or not ?

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[henchman24]

There are a few factors here. There is an unusable buffer where Tesla locks out a few percent (varies by model and battery chemistry, but 3-4% is normal for Tesla... 0.5-1% top and 2-3% bottom). This is to keep the pack from bricking and there isn't an overcharge event. Then, displayed 0% isn't actually 0%. There is about 3% of the battery that can be used below 0%. I think they do this so people don't get stranded as most won't test how far they can go below zero.

So even on a fresh, fresh battery... 0-100% indicated is really more 6% to 99% or over ~114 kWh. With about 119-120 usable.

Then you get into degradation. Within the first few thousand miles, you'll lose 2-3% and then the degradation will start to slow... though still within the first ~30-40k mi, you should expect to lose 5%. There are a ton of factors and variations here, but this would be normal. So with that, fairly early on, the 0-100% indication would really be around 110 kWh.

Temp also plays a role here. If the pack goes from 90 degrees to say 50 degrees... the percentage will go down a percent or two due to the voltage drop from that (and you can't use as much batter at 50 vs 90). Now when you run consistently the pack temps tend to level, but over the course o a week if it was 90 degrees and you hit a cold spell... some displayed percentage will be lost due to the voltage drop (and it really isn't lost).

Additionally, the energy monitoring of wh/mi is when the vehicle is on. It does not count any vampire drain from being off. Or parked on a hot day where battery cooling happens while you're in a store. Dog mode, keep, etc are not counted in this efficiency. Sitting in the vehicle with climate on though is counted.

Lastly... BMS sway. The monitoring of percentage in Teslas is really quite good compared to the larger ev market, but it isn't perfect. It is based on voltage, balanced cells with tracking the flow of power each way. If you never charge above 93-94%, you'll start to see some sway. Where 8% could mean 11%, it could mean 6% as the voltage is close enough that it could be either. This doesn't really hurt anything and you shouldn't go out of your way to charge >95%, but is makes the percentage displayed vary a bit.

Anecdotally, I've pulled 118 kWh out of my pack before on one long drive and had 1% indicated remaining. There are manufacturing variances so not all packs will be exactly 122.4 kWh, but that size (or slightly more) fits with what I pulled out of my pack.

 

[henchman24]

Reserve is at least 10%, but possibly 15%. Can't say if that's how it's done in CT, but in the industry the common practice is to leave 10% at the bottom and 5% at the top, so the actual cycling of the battery is 10-95%.

It used to be common to have higher buffers, but that is really lessening throughout the auto industry. Batteries have proven to be reliable enough that they have opened up the buffers.

Tesla has never really had much of a buffer though. They used to do ~6-7% at the bottom with nothing at the top (early Model S days), but have switched to a ~3-4% bottom and 0.5-1% top. LFP chemistry vehicles have nothing at top and ~2% bottom.

Also another thing... do we know how the energy tracker works ? Is it really total energy used per mile traveled, or is it energy used in the traction subsystem only ? In other words if you sit in a parking lot with AC on for an hour, does it count it towards the current trip or not ?

Rule of thumb, you are in gear or can shift into gear, it is counted. If you can't shift into gear, it is not counted.

 

[webspeedracer]

There are a few factors here. There is an unusable buffer where Tesla locks out a few percent (varies by model and battery chemistry, but 3-4% is normal for Tesla... 0.5-1% top and 2-3% bottom). This is to keep the pack from bricking and there isn't an overcharge event. Then, displayed 0% isn't actually 0%. There is about 3% of the battery that can be used below 0%. I think they do this so people don't get stranded as most won't test how far they can go below zero.

So even on a fresh, fresh battery... 0-100% indicated is really more 6% to 99% or over ~114 kWh. With about 119-120 usable.

Then you get into degradation. Within the first few thousand miles, you'll lose 2-3% and then the degradation will start to slow... though still within the first ~30-40k mi, you should expect to lose 5%. There are a ton of factors and variations here, but this would be normal. So with that, fairly early on, the 0-100% indication would really be around 110 kWh.

Temp also plays a role here. If the pack goes from 90 degrees to say 50 degrees... the percentage will go down a percent or two due to the voltage drop from that (and you can't use as much batter at 50 vs 90). Now when you run consistently the pack temps tend to level, but over the course o a week if it was 90 degrees and you hit a cold spell... some displayed percentage will be lost due to the voltage drop (and it really isn't lost).

Additionally, the energy monitoring of wh/mi is when the vehicle is on. It does not count any vampire drain from being off. Or parked on a hot day where battery cooling happens while you're in a store. Dog mode, keep, etc are not counted in this efficiency. Sitting in the vehicle with climate on though is counted.

Lastly... BMS sway. The monitoring of percentage in Teslas is really quite good compared to the larger ev market, but it isn't perfect. It is based on voltage, balanced cells with tracking the flow of power each way. If you never charge above 93-94%, you'll start to see some sway. Where 8% could mean 11%, it could mean 6% as the voltage is close enough that it could be either. This doesn't really hurt anything and you shouldn't go out of your way to charge >95%, but is makes the percentage displayed vary a bit.

Anecdotally, I've pulled 118 kWh out of my pack before on one long drive and had 1% indicated remaining. There are manufacturing variances so not all packs will be exactly 122.4 kWh, but that size (or slightly more) fits with what I pulled out of my pack.

Kyle’s Out of Spec 70mph test 100%-0% used an indicated 124kWh, discussed at 39:39 here in his summary of the test:

 

[henchman24]

Kyle’s Out of Spec 70mph test 100%-0% used an indicated 124kWh, discussed at 39:39 here in his summary of the test:

Yup... that fits. Most manufacturing variation on batteries would have them slightly above the rating and 124 is easily in that variation. Especially on a very, very fresh pack.

 

[TyPope]

You're missing all the charge lost when the truck is not moving. Look at the Park screen under Energy. That amount, 10.6% needs to be added to get your full amount used since last charged.

If you want to see what the truck's BMS is calculating for your battery size, go to the Energy Consumption screen. Multiply the efficiency over the last 200mi, 285.0Wh/mi, times the projected range, 175mi, then divide the total by the remaining SOC, 41%, and you get: 121.6kWh:

Wow. This was very well written and explained. I didn't have questions but still learned from this. Kudos, kind sir.

 

[Beetlebug62]

I don't know what the pack size is when new, nor what the Cybertruck's top or bottom buffers are; but, this is the data from my 2018 Model 3 LR-AWD. I have an OBDII connector and the ScanMyTesla app, which gives me the raw data.

So, there's variation for a full pack, as different mfrs make the cells, so some packs have 77.8kWh and some later ones had ~81kWh. But, the EPA rated amount was the same, so anything above that was considered the top buffer. So, while your battery was degrading in the top buffer, it showed 100% EPA rated range. Mine did for 6 full years, before starting to drop below 75kWh. Now about 6% deg.

And the 3.48kWh showing for the Energy buffer, was the bottom buffer.

 

[CWiley]

Can someone please help me understand this? 370 wh/mi is awesome efficiency but this doesn’t add up to a 122kwh battery. At 405wh/mile a 122kwh battery should give the stated range of 300 miles. At 370 wh/mile it should be a lot more. Battery seems to be a lot smaller than 122.
----------------------
Below should be 123kwh battery: (123000kw)
-----------------------

 

[henchman24]

Can someone please help me understand this? 370 wh/mi is awesome efficiency but this doesn’t add up to a 122kwh battery. At 405wh/mile a 122kwh battery should give the stated range of 300 miles. At 370 wh/mile it should be a lot more. Battery seems to be a lot smaller than 122.
----------------------
Below should be 123kwh battery: (123000kw)
-----------------------

What are you trying to figure out here?

 

[Cirrus SR22]

I’m gonna guess you started at 80-81% SoC. Did a similar trip last Sat; 225 miles round trip, ~380wh/mile avg, and ended at ~15% SoC. However, I started with ~85% SoC.

I started at 97 SOC, that’s why I believe the battery is not 122kwh

Did you start at 100% or was your last charge to 80% or something?

started at 97%

 

[henchman24]

I started at 97 SOC, that’s why I believe the battery is not 122kwh

started at 97%

At >7k miles, your battery is likely under 122kWh. It is probably ~120kWh now, but reasonably could be 118/119 in in the normal of degradation. Additionally the 0-100% is not the actual 0-100% you can't use all the battery AND there is battery available under 0%. It is more like 6-99% in reality. Then you have BMS sway where that indication can be 2-4% off very easily. You may have used as little as 82-83% in that period in actuality. Then you get into other things like keep climate, dog mode, cabin overheat, general vampire drain that is not counted in that figure.

There are two ways to really test the battery. The test mode (which may have already been taken out of service mode on the customer facing side), or to go on one long, continuous drive with no breaks or massive changes in speed until you completely run out of battery. Anything else is a pure guess.

If you are really worried about it, simply have Tesla test it. It is possible you have a bad pack. It is well verified that the CT battery is 122.4 kWh (within manufacturing tolerances where companies error on the conservative side... so most see 123-124). This is EPA (and other foreign agency) rated and Tesla has to provide the backup for that. We also have enough public data to support that number too (even a tad bit above).

 

[Beetlebug62]

Can someone please help me understand this? 370 wh/mi is awesome efficiency but this doesn’t add up to a 122kwh battery. At 405wh/mile a 122kwh battery should give the stated range of 300 miles. At 370 wh/mile it should be a lot more. Battery seems to be a lot smaller than 122.
----------------------
Below should be 123kwh battery: (123000kw)
-----------------------

No clue as to what was written above. You need the current SOC to calculate how large the battery is, according to the BMS. Think of what this is showing you. It's the BMS' calculation of remains range, based upon what it thinks your battery capacity is, and your last 200mi of driving efficiency.

Based upon that, the BMS thinks you can go an additional 230mi. I will bet your SOC was ~80%.

Basically, you have 2 of the 3 pieces of info you need to figure out what the BMS is calculating. There's no need to do all the math you did above. The truck is showing you all the data for you to figure out what the BMS thinks is your pack size.

 

[CyberGus]

Reverse the problem: look at your charging. If charging from 50% to 100% takes 61kWh, then you can extrapolate a 122kWh total capacity.

 

[CWiley]

No clue as to what was written above. You need the current SOC to calculate how large the battery is, according to the BMS. Think of what this is showing you. It's the BMS' calculation of remains range, based upon what it thinks your battery capacity is, and your last 200mi of driving efficiency.

Based upon that, the BMS thinks you can go an additional 230mi. I will bet your SOC was ~80%.

Basically, you have 2 of the 3 pieces of info you need to figure out what the BMS is calculating. There's no need to do all the math you did above. The truck is showing you all the data for you to figure out what the BMS thinks is your pack size.

Agreed, lot of unnecessary math. I was attempting to illustrate to @Cirrus SR22 how the battery size is approx. 122-123kwh. And how hard you drive the vehicle plays a large part on the range you get.

Also,
«Think of what this is showing you. It's the BMS' calculation of remains range, based upon what it thinks your battery capacity is, and your last 200mi of driving efficiency."

That page is actually showing your estimated range remaining based on the present % of battery, in conjunction with your driving habits over the past 200 miles respectively.

The baseline (Rated) is approx. 406 Wh/mi (for tri-motor) Which is why it can tell you that you have used more or less than what was "Rated."

 

[CWiley]

No clue as to what was written above. You need the current SOC to calculate how large the battery is, according to the BMS. Think of what this is showing you. It's the BMS' calculation of remains range, based upon what it thinks your battery capacity is, and your last 200mi of driving efficiency.

Based upon that, the BMS thinks you can go an additional 230mi. I will bet your SOC was ~80%.

Basically, you have 2 of the 3 pieces of info you need to figure out what the BMS is calculating. There's no need to do all the math you did above. The truck is showing you all the data for you to figure out what the BMS thinks is your pack size.

Long winded way of saying:
A 123Kwh battery with an estimated 406.9 Wh/mi "Rated" baseline will give you the estimated 302 (give or take) mile range estimated for the Cyberbeast.

However, how hard or how efficiently you drive is a large factor in achieving that range.

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