Percentage or Miles/Kilometers : which do you use and why?

[Snow Drift]

Yes they do. That is because miles are not based on EPA - they are based on the energy the car thinks is available.

Because when it degrades or is imbalanced it will display a smaller number for a full charge.

The car says 310 @ 100%...but that is not necessarily how far you will travel. That 310 is based on the EPA rating provided by Tesla. 90% is an actual reading, and you can make an assumption based on it. Just like if your ICE has quarter of a tank left, you have a basic idea how far you can go, regardless of EPA.

Once you charge to 90% the software adjusts back to 310 miles.

I believe the default is to use percent and miles is only presented to help with converting ICE drivers to electric. My phone doesn't say hours, it says battery %.

 

[darth_vad3r]

So for all those who use % remaining because they feel that is more reliable....When your battery degrades do you think that the car will degrade in % when you charge? Meaning, if your car's battery has degraded 10% do you think when you do a full charge it will say 90%? If it does, then great, but if it doesn't then it is just a useless.

Would be great to hear from someone who has measurable degradation(by actual drive testing) to share what % and miles shows.

There are tons of posts about this. Set charge limit to x%, used to stop charge at y miles, now only get z miles.

 

[Snow Drift]

The degradation issue is exactly why miles is more reliable to use!

You quoted me before I edited to clarify a bit, but what’s more reliable?

(a) “155 miles remains” means half of your original capacity for the life of the car, or
(b) “50%” mean’s half of your current capacity, which could be same as above on day 1, or 45% of original capacity if you have -10% degradation.

They don’t tell you what “100%” is equivalent to unless you display miles and back-calculate from current % to extrapolate or charge to 100%. If you display miles or km, you know how much energy the pack thinks it has. If you display %, you know it ti is it has x% of some other number you don’t know.

They don't tell you bc it is different for every situation and might not equal the original quote. So if it says 155 miles and you only go 150 people will complain. If it says 50%, the driver makes an assumption as to how far that will take you.

 

[darth_vad3r]

The car says 310 @ 100%...but that is not necessarily how far you will travel. That 310 is based on the EPA rating provided by Tesla. 90% is an actual reading, and you can make an assumption based on it. Just like if your ICE has quarter of a tank left, you have a basic idea how far you can go, regardless of EPA.

Once you charge to 90% the software adjusts back to 310 miles.

I believe the default is to use percent and miles is only presented to help with converting ICE drivers to electric. My phone doesn't say hours, it says battery %.

No, no, no, you are missing that the actual “gas tank” is shrinking over time.

 

[darth_vad3r]

Let’s use numbers here.

Let’s say my SR+ has a 50kWh capacity and that is 240 EPA miles.

1) At “120 miles”, how many kWh of energy does an SR+ have “in the tank”?
Answer: 25kWh

2) At “50%” how many kWh of energy does an SR+ have “in the tank”?
Answer: trick question. Nobody knows, it depends if you have degradation or not, if the car is new it could be 25kWh, if you have severe degradation it could be only 20kWh.

Which is a more reliable way to gauge energy content in your car?

 

[Snow Drift]

Let’s use numbers here.

Let’s say my SR+ has a 50kWh capacity and that is 240 EPA miles.

1) At “120 miles”, how many kWh of energy does an SR+ have “in the tank”?
Answer: 25kWh

2) At “50%” how many kWh of energy does an SR+ have “in the tank”?
Answer: trick question. Nobody knows, it depends if you have degradation or not, if the car is new it could be 25kWh, if you have severe degradation it could be only 20kWh.

Which is a more reliable way to gauge energy content in your car?

Can anyone prove that the rated miles on the screen is adjusted down due to degradation? Or are we only seeing the miles reduced due to imbalance (which adjusts back once you go to 90% a few times).

Rated Miles Day 1 = 100% = 310 miles
Rated Miles Day X = 100% = 279 miles (after 160,000 miles -10% loss) - Does this actually show up, or will it still show 310?

 

[darth_vad3r]

Can anyone prove that the rated miles on the screen is adjusted down due to degradation? Or are we only seeing the miles reduced due to imbalance (which adjusts back once you go to 90% a few times).

Rated Miles Day 1 = 100% = 310 miles
Rated Miles Day X = 100% = 279 miles (after 160,000 miles -10% loss) - Does this actually show up, or will it still show 310?

Search.

 

[David29]

I use percentage. I learned early on in my ownership (from wiser and more experienced owners here on TMC) that the battery SOC gauge is notoriously unreliable at indicating range in miles. When I want or need to know my remaining range in miles, I use the Energy app, which reflects my driving and the current conditions.

When set to distance, the SOC indicator simply shows battery charge in % times the Wh/mile (or Wh/km) number derived form the EPA range. So it is no more accurate for miles than the % is, and is not reflective of temperature, driving style, etc. In short, it is not only unreliable as an indicator of range, it is actually misleading. (As someone else said above, it might be accurate if you live in a climate where you can always achieve the EPA rated miles, and don't encounter extreme weather or drive in any extreme way.)

I see countless questions on this topic here and on other forums from newbies worried about their battery degradation, why their car used X miles of range to go Y miles, etc. So using distance as the indicator causes stress, and is mostly wrong to boot. Use the Energy app and be better informed.

 

[derotam]

There are tons of posts about this. Set charge limit to x%, used to stop charge at y miles, now only get z miles.

But those all those posts where people say they "only get z miles" are saying that they car only SHOWS z miles. They aren't drive testing the vehicle.

Let’s use numbers here.

Let’s say my SR+ has a 50kWh capacity and that is 240 EPA miles.

1) At “120 miles”, how many kWh of energy does an SR+ have “in the tank”?
Answer: 25kWh

Ahh yes I love this one...so you have two variations here...
1) If rated miles actually changes with battery degradation(and SOC stays at 100% for full charge) then "120 miles" would be accurate(IAW EPA testing cycle), and SOC % would be BS

2) If rated miles still shows 310(or 325) at 100% SOC with battery degradation then both rated miles, and SOC are BS

So basically we don't know which is true BECAUSE I haven't seen the people who show less than 310(or325) at 100%, prove that they have actual degradation.

I argue against the SOC % until someone can show me that they car with battery degradation only charges to less tan 100%.

I'm not saying rated miles is perfectly accurate but it gives a better immediate value. Also, if at 100% SOC you show 310 miles, and at 50% you show 155 miles, and 25% it shows 77 or 78 miles, then it is being just as accurate as SOC%.

 

[AlanSubie4Life]

battery SOC gauge is notoriously unreliable at indicating range in miles.

It is not surprising that it is bad at indicating range in miles, because it is a display of energy. It happens to be have units of "miles", but in this case, it's rated miles, which are effectively a unit of energy. So yes, it does a very bad job at indicating miles available, since that is not what it is displaying! It is understandably confusing, since usually people think of "miles" as a unit of distance...but it's not in this case.

When set to distance, the SOC indicator simply shows battery charge in % times the Wh/mile (or Wh/km) number derived form the EPA range

I'm not sure what you mean here (you are discussing the distance setting so % doesn't play into this statement). I would rephrase that "it shows battery energy equal to the displayed rated miles times the Wh/rmi constant derived roughly from EPA testing." I think that's what you meant.

I see countless questions on this topic here and on other forums from newbies worried about their battery degradation, why their car used X miles of range to go Y miles, etc. So using distance as the indicator causes stress, and is mostly wrong to boot.

Yes, it is confusing. The root cause of this is the confusion over what the gauge is showing when set to miles:

Miles - it is showing the remaining energy left in the pack (best estimate of the BMS system)
Percentage - it is showing the % of the energy left relative to a full pack for that specific pack (whatever that may be).

I like to know how much energy I have left, so I use miles.

 

[derotam]

Can anyone prove that the rated miles on the screen is adjusted down due to degradation? Or are we only seeing the miles reduced due to imbalance (which adjusts back once you go to 90% a few times).

Rated Miles Day 1 = 100% = 310 miles
Rated Miles Day X = 100% = 279 miles (after 160,000 miles -10% loss) - Does this actually show up, or will it still show 310?

Need someone with actual degradation to say anything... And that has to be determined by drive testing.

Search.

That is a cop out...it is insane to think someone could quickly search this topic and actually find an appropriate answer. If you have a specific source, post it please.

 

[AlanSubie4Life]

So basically we don't know which is true BECAUSE I haven't seen the people who show less than 310(or325) at 100%, prove that they have actual degradation.

Agreed we may not know for Model 3, but presumably we know how Tesla treats this for Model S/X and presumably they will be consistent. That's my assumption here.

I argue against the SOC % until someone can show me that they car with battery degradation only charges to less tan 100%.

My understanding is that with Model S/X, degraded batteries will show 100% or close to it (as you would expect). But I guess I don't 100% know since I have no personal experience.

I'm definitely making what I think are reasonable assumptions about how degradation will be treated (I would expect it to be treated similarly to a battery imbalance).

I know on the defective Model 3 packs reported so far (there was one over the winter that got a battery replacement, posted about here), they don't show the full rated range! That much I do know. That one was was about half the original rated range. So that supports one of the assumptions. I don't know what it displayed in %, though.

 

[derotam]

Agreed we may not know for Model 3, but presumably we know how Tesla treats this for Model S/X and presumably they will be consistent. That's my assumption here.



My understanding is that with Model S/X, degraded batteries will show 100% or close to it (as you would expect). But I guess I don't 100% know since I have no personal experience.

If that is true then SOC% is worthless to use for the driver for an appropriate distance gauge. I do not recall Model S/X owners complaining about the rated miles fluctuating like some people are seeing in the Model 3...I could easily be wrong though since I don't really monitor the S/X side.

 

[AlanSubie4Life]

SOC% is worthless to use for the driver for an appropriate distance gauge

*energy

Neither quantity has any relation to distance. Rated miles is a unit of energy, and % is a dimensionless quantity. (That much we DO know...no assumptions needed.)

But agreed, if that is true, SOC% is less useful. I wouldn't call it worthless since most of the time it would be fine, and you can always briefly swap and see where your battery is at, to "recalibrate".

 

[derotam]

*energy

Neither quantity has any relation to distance. Rated miles is a unit of energy, and % is a dimensionless quantity. (That much we DO know...no assumptions needed.)

But agreed, if that is true, SOC% is less useful. I wouldn't call it worthless since most of the time it would be fine, and you can always briefly swap and see where your battery is at, to "recalibrate".

True, but gasoline has an energy rating also so they could have said joules per mile based on energy content of gasoline and efficiency of the vehicle.

It's all energy. People think in miles though, not "yeah I'm traveling 25kWh today" haha

 

[tesatx]

Why not displaying both all the time?

Yeah, wish we could do that...

 

[jerry33]

*energy

Neither quantity has any relation to distance. Rated miles is a unit of energy, and % is a dimensionless quantity. (That much we DO know...no assumptions needed.)

But agreed, if that is true, SOC% is less useful. I wouldn't call it worthless since most of the time it would be fine, and you can always briefly swap and see where your battery is at, to "recalibrate".

From what I can tell, there are four ways to figure this out:
1. Ideal miles: Tesla appears to mess with this less than with Rated miles, so its what I use to determine degradation. It's also what I use for normal driving because my driving matches close to Ideal miles.
2. Rated miles: This is closer to most folk's driving. I started using it but it was so conservative, I started using Ideal miles. This is basically EPA energy usage based on how much energy is the system thinks the battery has.
3. Percentage. Mostly useful for a degradation calculation. Note that the only real way is to fill and drain the battery a couple of times, but that's hard on the battery.
4. Percentage on the Nav. This is the best way for trips. Set a destination and charge until there is a comfortable percentage. In nice weather this might be 5% (for me), in very bad weather it might be 30%. Watch the percentage as you drive and adjust driving so that the percentage remains the same or increases. It's not uncommon for the percentage to increase 10-20% during the trip. YMMV

 

[jerry33]

Yeah, wish we could do that...

You used to be able to do that, but it was changed early on.

 

[darth_vad3r]

Need someone with actual degradation to say anything... And that has to be determined by drive testing.



That is a cop out...it is insane to think someone could quickly search this topic and actually find an appropriate answer. If you have a specific source, post it please.

You don’t trust the canbus data? You want a test drive to prove anything? Then you won’t trust the test either?

Your theory [Edit: maybe not your theory, the “other theory”] goes against common knowledge on the forum so IMO you have to disprove it with testing. I have nothing to prove. You can believe your theory if you wish.

It’s clear that displayed miles and displayed % diverge, for whatever reason (degradation, imbalance, etc). If they diverge, how do you explain it?

% is “percent of what the car thinks its max current capacity is” (current energy content E divided by max M)
miles is “current energy content multiplied by a constant” (E * C)

How do you think the numbers are calculated if that is wrong?

 

[darth_vad3r]

True, but gasoline has an energy rating also so they could have said joules per mile based on energy content of gasoline and efficiency of the vehicle.

It's all energy. People think in miles though, not "yeah I'm traveling 25kWh today" haha

I don’t think in miles (or kilometres). I think in energy because it’s used when I’m not driving too, like keeping the AC on for an hour while parked in the sun, or leaving Sentry mode on, etc. I use the km display as a gauge of energy content in my battery. One “km” is one “energy unit”. It should be the same today and 10 years from now.