Estimate cost of charging a Dual Motor

[Chris9702L]

If my electrical company charges 11 cents per kWh can anyone take a rough guess on how much it will take to charge up a Dual Motor version?

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[HaulingAss]

A 250 mile range Dual Motor probably entails a 110 kWh pack (give or take). Most people don't run them all the way down or charge them to 100% but a full charge of a 110 kWh battery (from 0% to 100%) would take 110 kWh plus around 10% for inefficiencies so 121 kWh or about $13.30 at $0.11/kWh.

A more common charge would be 40%-80% which would cost about $5.32. With normal driving in normal weather that would be enough to get you about 100 miles. Of course, no oil changes.

 

[Ogre]

It's likely to cost somewhere between $0.04-0.05 per mile to charge your truck at home.

As @HaulingAss suggests, "Filling Up" your Cybertruck will rarely be a thing. Most of the time EVs bounce around between 30% charge and 70% charge. You would only "fill up" if you got home with the range exhausted and needed to travel your full range the next day. I don't think that's ever happened to me.

 

[ajdelange]

If my electrical company charges 11 cents per kWh can anyone take a rough guess on how much it will take to charge up a Dual Motor version?

All 3 of the models will use around .45 kWh to go 1 mile in nominal driving so the nominal cost per mile where the cost of electricity is 11¢/kWh is simply 0.45*11/.9 = 5.5¢/mi. The 0.9 is in there because Level 2 charging is about 90% efficient.

The cost of a charge depends on how many miles you are replacing at the particular charging session. If you drive 40 miles round trip to work and charge at night to the same level each evening, as most of us do, then you will need to replace the 40 miles plus 5 - 10 miles phantom drain for a total of 50. The cost for this would be 50*.0495 = $2.75.

You will find it really helpful to think in terms of % SoC. If the dual has rated range of 250 mi then each percent SoC is 2.5 mi and costs 2.5*5.5 = 5.5/.4 = 13.75¢ and 2.5*.45* 28 = 31.5¢ at a supercharger. It's clear from this that a full charge (not that one would ever do it except as an experiment) is $13.75 at home and $31.50 at a Supercharger.

For daily driving you typically charge your BEV to 70% each night and leave with 0.7*250 = 155 miles range on board in the morning. If you do 40 miles of nominal (mix of in town and highway driving) with 5 phantom you will have used about 45/250 = 18% of the battery and the gauge will read about 52% when you get home. You know another 5 miles phantom will be incurred overnight which is another 5/250 = 2% so you will need to replace 20% to be back at 70% next morning. At 13.75¢/% the cost will be $2.75 as before.

A situation frequently arises in this household where you find that you are going to drive further than your nominal that day and want to arrive at some destination or back home with a healthy margin. You decide to add 20% and depart with 90% SoC. You easily calculate the cost of the extra 20% but in this case you are probably more concerned about the cost in the time required. This is calculated in the same way as the cost in $. A 40 Amp charger delivers 0.9*240*40 = 8640 W (again considering the 90% charging efficiency). With consumption of 450 Wh/mi the charging rate is 0.9*240*40/450 = 19.2 mph. That's 7.68% of the rated range per hour. As the goal here is simplicity we'll round that to 8% per hour or .125 hour per percent so that you can easily calculate that the extra 20% will take 2.5 hours. For a 48 A charger the rate is 9.2% per hour. That's .1085 hour per percent. Round it to .11 and the calculation is easy. Adding 20% would require 2.2 hr additional charging.

The point of all this is that it relies only on rated range and rated consumption. Battery size has not even been mentioned. It all applies equally to the TriMotor except that its rated range is 5 miles/% (and, consequently, has a battery twice as big).

As you drive your truck it accumulates data on consumption and miles driven and thus on your actual consumption which will not be the rated consumption. For some it is quite close to the rated consumption but for others (those who drive primarily on freeways with speed limits above 65, those who can't resist coming out of every stop sign and traffic light as if they are race car drivers..) it will be higher. What I have given here is a set of nominal numbers. If your actual consumption is more or less you will learn how to adjust from nominal if you care to make the effort.

 

[Throwcomputer]

All 3 of the models will use around .45 kWh to go 1 mile in nominal driving so the nominal cost per mile where the cost of electricity is 11¢/kWh is simply 0.45*11/.9 = 5.5¢/mi. The 0.9 is in there because Level 2 charging is about 90% efficient.

The cost of a charge depends on how many miles you are replacing at the particular charging session. If you drive 40 miles round trip to work and charge at night to the same level each evening, as most of us do, then you will need to replace the 40 miles plus 5 - 10 miles phantom drain for a total of 50. The cost for this would be 50*.0495 = $2.75.

You will find it really helpful to think in terms of % SoC. If the dual has rated range of 250 mi then each percent SoC is 2.5 mi and costs 2.5*5.5 = 5.5/.4 = 13.75¢ and 2.5*.45* 28 = 31.5¢ at a supercharger. It's clear from this that a full charge (not that one would ever do it except as an experiment) is $13.75 at home and $31.50 at a Supercharger.

For daily driving you typically charge your BEV to 70% each night and leave with 0.7*250 = 155 miles range on board. If you do 40 miles of nominal (mix of in town and highway driving) with 5 phantom you will have used about 45/250 = 18% of the battery and the gauge will read about 52% when you get home. You know another 5 miles phantom will be incurred overnight which is another 5/250 = 2% so you will need to replace 20% to be back at 70% next morning. At 13.75¢/% the cost will be $2.75 as before.

A situation frequently arises in this household where you find that you are going to drive further than your nominal that day and want to arrive at some destination or back home with a healthy margin. Do you decide to add 20% and depart with 90% SoC. You easily calculate the cost of the extra 20% but in this case you are probably more concerned about the cost in the time required. This is calculated in the same way as the cost in $. A 40 Amp charger delivers 0.9*240*40 = 8640 W (again considering the 90% charging efficiency). With consumption of 450 Wh/mi the charging rate is 0.9*240*40/450 = 19.2 mph. That's 7.68% of the rated range per hour. As the goal here is simplicity we'll round that to 8% per hour or .125 hour per percent so that you can easily calculate that the extra 20% will take 2.5 hours. For 48 A charger the rate is 9.2% per hour. That's .1085 hour per percent. Round it to .11 and the calculation is easy. Adding 20% would require 2.2 hr additional charging.

The point of all this is that it relies only on rated range and rated consumption. Battery size has not even been mentioned. It all applies equally to the TriMotor except that its rated range is 5 miles/% (and, consequently, has a battery twice as big).

As you drive your truck it accumulates data on consumption and miles driven and thus on your actual consumption which will not be the rated consumption. For some it is quite close to the rated consumption but for others (those who drive primarily on freeways with speed limits above 65, those who can't resist coming out of every stop sign and traffic light as if they are race car drivers..) it will be higher. What I have given here is a set of nominal numbers. If your actual consumption is more or less you will learn how to adjust what the nominal numbers tell you if you care to make the effort.

So you can set in app/car/charger where you want the charge to stop overnight instead of just let it charge till full or wherever it gets to by the time you unplug?

 

[Ogre]

So you can set in app/car/charger where you want the charge to stop overnight instead of just let it charge till full or wherever it gets to by the time you unplug?

Yep.

You just drag the little caret under the battery and it moved the line. When the charge hits that line, it stops charging and notifies you. Most of the time mine sites around 200-250 miles max charge.

There is a similar control on the console.

 

[Throwcomputer]

Is there a battery longevity reason for this, or a charging cost savings reason for this?

Does it reduce the battery life if you always charge to full, like most modern electronics or does it just waste electricity because it cost exponentially more power to charge that last 20% or so?

 

[ajdelange]

So you can set in app/car/charger where you want the charge to stop overnight instead of just let it charge till full or wherever it gets to by the time you unplug?

Yes. That's how it works. And yes you can do that via the car's charging screen, via the Tesla App or via third party apps such as TeslaFi and Stats.

You rarely want to set a charge level greater than 90%. In fact if you do that the car will admonish you not to.

 

[ajdelange]

It's a battery longevity issue. Charging isn't less efficient at higher levels.

While we're on the subject I'll mention that you can tell the car when you want to leave in the AM. It will start charging in order to complete at the specified time. This is helpful in cold climates as the battery is warm when you depart.

 

[Throwcomputer]

It's a battery longevity issue. Charging isn't less efficient at higher levels.

That's what i figured. So when you map a long distance route and it charts all the charging spots for you, the reason it gives different charging times at each stop is because it's figured the optimum amount of charge at each stop for gaps in charging locations/overall distance traveling AND what's best for battery life. And I'm guessing if you follow that planned route, it automatically sets the charging stop point for you at each stop based on what was planned in the route? So you don't have to do anything but set your end point at the beginning of trip, and make sure you pull over and plug in when it tells you to?

 

[ajdelange]

Essentially, yes. The main component of the planner's optimality criterion is minimization of time on the road. You have probably heard about the infamous "taper". Batteries can withstand high charge rates at low SoC but the charge rate at higher SoC must be limited. At high SoC the anode pockets are fuller and an arriving lithium ion is more likely to react irreversibly with some other part of the battery structure (SEI) and be lost. Thus quickest (highest miles added per minute) charging is realized at low charge level. The algorithm thus has you stop frequently for small charges in the lower part of the battery range to the extent possible and recognizing that each stop requires getting off the road and into and out of the charging station. It's pretty cool.

There is an application you should get now and start playing with called A Better Route Planner which was written originally to give a better alternative to the Tesla in car planner. They succeeded. It is pretty spiffy. For example it lets you modify your optimality criterion to minimize time or minimize the number of stops as you wish. Beyond that it will teach you a great deal about how your truck will operate along the routes you plan to travel.

 

[Throwcomputer]

I wasn't entirely clear... Just to clarify, the route planned maps out at x stop, charge to y, and the next stop after that, charge to different y. You literally don't have to pay attention to when to stop charging at each charge point cause it's in your planned route and it automatically charges to the planned amount "y" at each stop? I literally don't want to think about it after i create a route!

Good tip about that app. I'll check it out. I've been playing with Tesla's route planner website with the closest model to my expected model range.

 

[ajdelange]

I wasn't entirely clear... Just to clarify, the route planned maps out at x stop, charge to y, and the next stop after that, charge to different y. You literally don't have to pay attention to when to stop charging at each charge point cause it's in your planned route and it automatically charges to the planned amount "y" at each stop?

Yes. That's how it works with a couple of twists. If something happens such that the original plan isn't going to work out it will suggest modifications. The thing that really throws a monkey wrench into the works is rain. A an example It will take my nominal consumption of 280 Wh/mi up to 380 Wh/mi. If the car estimates that this extra will leave me shy at the next stop it will display a message saying that I should slow down to a specified speed or suggest an additional charging stop. OTOH you sometimes get lucky and a tail wind springs up which means you can skip a charging stop.

Also at a charging stop even though you have reached y and the truck has announced "Charging is sufficient to continue your trip" (or whatever the exact words are) you may choose to continue charging beyond y either to give you some extra margin because it looks as if it might rain or because you want to sit there and finish your bagel. A decision to do this, naturally, changes all subsequent charges. The planner will take this into account. You need do nothing.

I literally don't want to think about it after i create a route!

You can drive that way if you prefer and many do. But then there are guys like me. You may have guessed that I get a little geeky about this kind of stuff. I'm constantly monitoring the gauges and graphs and running "what if" scenarios in my head. That's how I relieve the monotony of long drives. You will do well to keep an eye on things at first. Eventually you will get familiar with the truck, the charging network, the world of BEV driving and the routes you operate over and it won't be necessary. When you go from A to B in your ICE vehicle you probably expect to gas up at C and D but may later learn of a really good diner at E and start refueling there. It is really pretty much the same with Tesla vehicles.

Good tip about that app. I'll check it out. I've been playing with Tesla's route planner website with the closest model to my expected model range.

There are free and paid versions. Before you get your truck the free version is fine. The paid version talks to your truck, takes current traffic and weather conditions along the route into consideration and shows you how busy charging stations are all in real or near real time. Great on an actual trip but for your current learning needs un-necessary.

 

[ajdelange]

There is one other cost that some like to consider and that is the CO2 emission involved. If your utility burns natural gas it emits about 0.9 lb CO2 per kWh generated. If it burns coal it is about 2.13 lbs. From No. 4 you should be able to figure the CO2 cost per mile or per % SoC.

 

[Throwcomputer]

Yes. That's how it works with a couple of twists. If something happens such that the original plan isn't going to work out it will suggest modifications. The thing that really throws a monkey wrench into the works is rain. A an example It will take my nominal consumption of 280 Wh/mi up to 380 Wh/mi. If the car estimates that this extra will leave me shy at the next stop it will display a message saying that I should slow down to a specified speed or suggest an additional charging stop. OTOH you sometimes get lucky and a tail wind springs up which means you can skip a charging stop.

Also at a charging stop even though you have reached y and the truck has announced "Charging is sufficient to continue your trip" (or whatever the exact words are) you may choose to continue charging beyond y either to give you some extra margin because it looks as if it might rain or because you want to sit there and finish your bagel. A decision to do this, naturally, changes all subsequent charges. The planner will take this into account. You need do nothing.

You can drive that way if you prefer and many do. But then there are guys like me. You may have guessed that I get a little geeky about this kind of stuff. I'm constantly monitoring the gauges and graphs and running "what if" scenarios in my head. That's how I relieve the monotony of long drives. You will do well to keep an eye on things at first. Eventually you will get familiar with the truck, the charging network, the world of BEV driving and the routes you operate over and it won't be necessary. When you go from A to B in your ICE vehicle you probably expect to gas up at C and D but may later learn of a really good diner at E and start refueling there. It is really pretty much the same with Tesla vehicles.

There are free and paid versions. Before you get your truck the free version is fine. The paid version talks to your truck, takes current traffic and weather conditions along the route into consideration and shows you how busy charging stations are all in real or near real time. Great on an actual trip but for your current learning needs un-necessary.

This is all cool.

Last question. If you do as you say and decide you want to finish your bagel and the charging target has been met, but you don't want to keep charging.. Does it require physically unplugging to stop the charge? Or do you click stop charging in the ui? So you could potentially not get an extra charge while you finish the bagel, but not have to get out to unplug?

I realize this is a stupid thing to do, because you would start getting charged for idle time at the charger while not charging, and i would actually just keep charging until I'm ready to go. I'm just trying to understand the actual real world mechanics of the car/charging ui and functionality.

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