kWh question

[Kymandu]

Hello all,

According to google an sr+ has approximately 50 kWh, just checked my kWh after going from 90% to 10% and it shows 27kwh. I don’t know the specifics of kWh, is it factoring only the driving portion? Does hvac not factor into kWh displayed usage?

Adding in the remaining 20% would land me around 32kwh?

 

[Sklith]

Did you park the car at any time while your car's State of Charge went from 90% thru 10%? Do you use Sentry Mode? Any energy consumed while the car's parked isn't counted on the trip meter.

 

[jjrandorin]

Hello all,

According to google an sr+ has approximately 50 kWh, just checked my kWh after going from 90% to 10% and it shows 27kwh. I don’t know the specifics of kWh, is it factoring only the driving portion? Does hvac not factor into kWh displayed usage?

Adding in the remaining 20% would land me around 32kwh?

It only calculates driving,

 

[camalaio]

I'm not sure which part you looked at to get 27kWh, can you clarify? That changes the response a little bit, but not much.

The trip meters will show all usage while the car is in Drive, including any climate control usage. Any energy used while parked (including cabin preconditioning, Sentry mode, etc.) will not show up on anything you can see in the car.

Also, the math must be done carefully. To get the energy at 100%, you divide by 0.8 (80%), and 27kWH/0.8 = 33.75kWh, which is a fair bit more.

You likely have energy usage that's not being accounted for in that 27kWh while parked.

 

[Kymandu]

Ah, I just grabbed it from the energy usage on the car screen from last charge. Thanks for the replies though that answers my question.

 

[AlanSubie4Life]

Ah, I just grabbed it from the energy usage on the car screen from last charge. Thanks for the replies though that answers my question.

And as covered in other threads (but not in detail in the "Constants" thread yet because things are still settling out on the Performance) - the 2021 SR+ has about 53.6kWh capacity when new. This means 204Wh/rmi. (53.6kWh/263rmi) And it's only 0.955*204Wh/rmi = 195Wh/drmi (displayed rated mile), because of the buffer.

So that means you have 0.955*53.6kWh = 51.2kWh between 263rmi and 0rmi, due to the 4.5% buffer.

So on the trip meter the most you'll ever see (if you don't drive below 0rmi) will typically be about 99% of that, or about 50.7kWh. For whatever reason it's hard to get it to count every last drop, even if you spend the entire time in drive.

So for your 80% scenario (assuming you have an undegraded battery) you should have seen 40.6kWh. You saw 27kWh.

As others have mentioned, the meters only count energy use when you're not in Park. So you used/lost about 13.6kWh while in Park. Not unusual at all - depends on Sentry use, time between charges, use of cabin pre-heating, etc., etc.

2/3 of your energy (in this scenario) was used to move the car, 1/3 of it was used for other features.

 

[Phlier]

As others have mentioned, the meters only count energy use when you're not in Park

Hey Alan, I hope you don't mind, but I'm singling out what I consider to be a very important point that I think a lot of people don't realize. The important part is in bold, italicized, underlined text.

I also don't think that a lot of people realize how much power is lost during charging.

It's really important to look at the big picture when you're trying to nail down the numbers. But you already know this, so that's kinda directed at everyone but you.

 

[AlanSubie4Life]

I also don't think that a lot of people realize how much power is lost during charging.

Yes, that's a separate topic from this, but a good rule of thumb when using the UMC at max rate of 32A is about 88% efficient, from AC mains to battery available energy. That's what Tesla gets when they charge the car in their labs for the EPA results. But somewhat of a side issue from the original topic here (which comes up about once a month or so). You'll do a bit better at 48A, seems to be about 92-93%.

I guess we should have a sticky for how the Trip Meter works, lol.

 

[jjrandorin]

Yes, that's a separate topic from this, but a good rule of thumb when using the UMC at max rate of 32A is about 88% efficient, from AC mains to battery available energy. That's what Tesla gets when they charge the car in their labs for the EPA results. But somewhat of a side issue from the original topic here (which comes up about once a month or so). You'll do a bit better at 48A, seems to be about 92-93%.

I guess we should have a sticky for how the Trip Meter works, lol.

If you and / or @camalaio are volunteering to write it, I am game to make it a sticky.

 

[camalaio]

If you and / or @camalaio are volunteering to write it, I am game to make it a sticky.

This is a situation where a wiki makes a lot more sense. Does this forum have any sort of collaborative post feature?

 

[jjrandorin]

This is a situation where a wiki makes a lot more sense. Does this forum have any sort of collaborative post feature?

(moderator note
I am not sure... i think there is a way to make a post a wiki but am looking into it.

EDIT:... there definitely is a way to make a new post a wiki, but I am looking into possible mechanics to creating such a post and having, say @camalaio and @AlanSubie4Life for example be able to edit it.)