Charging in RV parks

[Dreamer Ryan]

My wife and I have put down a deposit on a CT. It’ll be our first EV. We live year round in RV parks (Summer in Alberta, winter in Yuma). I am very unknowledgeable about electrical. Both parks have a plug for 50 amp, 30 amp, and 20 amp. Will we be able to charge the CT , but still use power for our RV ? ( as long as not doing laundry or a/c).
thanks

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[Fabville]

Do you typically use the NEMA 14-50 for your RV or the TT-30? Are you at the same site for several months? Tesla used to include the 14-50 adapter for the mobile connector with the Model S and X, but now you have to buy it separately.
https://shop.tesla.com/product/gen-2-nema-adapters

There’s also various splitters for a 14-50, this one gives you two 14-50 females, it could save you from unplugging, but you’d need to make sure you’re not charging the CT while running anything in your RV.

https://www.amazon.com/RV-Power-Spl...&linkCode=w00&linkId=&creativeASIN=B07D4PT7T6

Campgrounds can vary quite a bit on what they offer for power, even from one site to another at the same location. I’ve been to one where I only had access to a TT-30. I bought this third party adapter, it was quite slow since it’s only 110 volts.
https://www.evseadapters.com/products/tt-30-adapter-for-tesla-model-s-x-3-gen-2/

I’ve also been to a campground with a pair of Tesla destination chargers onsite. Just parked our Model X near their main building to charge which was only a short distance from our campsite.

 

[ajdelange]

Will we be able to charge the CT , but still use power for our RV ? (as long as not doing laundry or a/c).

Yes. If you use the Universal Charger that comes with the truck it will only take 32 A (7.7 kW) from an 14-50R leaving 18 A (4.3 kW) for the RV assuming you are using a splitter. Thus you could run the RV and charger at the same time as long as you are sure that the RV load is less than 4.3 kW as you could do, for example, by setting the CT charge time to start after you go to bed. You can also set the charger to charge at a lower rate, say 20 A, so that there are 30A (7.2 kW) available to the RV. Of course charging time will go up. A more expensive approach is the Electric Range Buddy which is a fancy splitter that feeds the CT unless any load is presented by the RV in which case it shuts the CT off until the RV load goes away. https://www.bsaelectronics.com/prod...-50-cable-to-two-14-50-outlets-with-kwh-meter.

I think the first approach is probably more sensible as it will save you $$ and I suspect the Buddy has a non adjustable low threshold such that even if the refrigerator came on it might shut charging down.
[Edit]It switches over at 3.5 amps draw by the RV. I should be a simple matter to modify that switchover threshold but I would have to see the design before stating that it can be done as established fact.

If each campsite has 50A and 30A receptacles then another alternative is to put the RV on the 14-50R and charge from the 30A circuit (there is an adapter). But be aware that 30A outlets at RV parks are 30A @ 120 so that you would only have 3..6 kW available to the charger if you do this.

In any case the answer is not only yes, even with laundry or A/C on, (I wouldn't stretch it to both) but that you have quite a bit of flexibility in how you go about it.

I guess what I would do is hook up the RV at home and measure the consumption. It's not going to be 50A except perhaps when running the clothes dryer with the A/C on but probably not even then. Subtract the measured load from 50 A and set the charger to use that number when at the campground. Don't charge when you need to dry laundry. Do the same for other times i.e. at night with A/C, at night without etc. and set the truck to take whatever is left over. You will figure it out pretty quickly.



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[Fabville]

In case you ever need faster charging to go somewhere, there’s a supercharger in Yuma too.

 

[ajdelange]

We should probably talk a bit about what 32A, the maximum available from a 14-50R, implies. Before doing that I'll mention that it is possible to get 48A (the maximum the truck will take) from a 14-50R but I'm not going to go into that as someone who admits he is not knowledgeable about electricity shouldn't do it which is why the Tesla charger will only take 32A ( 7.68 kW) from a 14-50R. As the charger is not 100 % efficient that means about 7 kW delivered to the battery from a 14-50R . The CT is going to require about half a kW hour to travel 1 mile unloaded (no trailer). That means the 7 kWh delivered by a 7 kW charging rate in one hour will add about 14 miles of range to the truck. But if you are concerned about a RV that plugs into a 14-50R with A/C and clothes dryer you are talking a hefty towing load and the range added in an hour of charging will be more like 5 - 7 miles and even less than that if your trip home is uphill (but better than that if it is downhill). This not only implies long charging times at lower charging rates but makes it clear that the CT you got all excited about because it has 500 miles EPA range may only deliver 100 - 200 when towing a trailer.

 

[Dids]

We should probably talk a bit about what 32A, the maximum available from a 14-50R, implies. Before doing that I'll mention that it is possible to get 48A (the maximum the truck will take) from a 14-50R but I'm not going to go into that as someone who admits he is not knowledgeable about electricity shouldn't do it which is why the Tesla charger will only take 32A ( 7.68 kW) from a 14-50R. As the charger is not 100 % efficient that means about 7 kW delivered to the battery from a 14-50R . The CT is going to require about half a kW hour to travel 1 mile unloaded (no trailer). That means the 7 kWh delivered by a 7 kW charging rate in one hour will add about 14 miles of range to the truck. But if you are concerned about a RV that plugs into a 14-50R with A/C and clothes dryer you are talking a hefty towing load and the range added in an hour of charging will be more like 5 - 7 miles and even less than that if your trip home is uphill (but better than that if it is downhill). This not only implies long charging times at lower charging rates but makes it clear that the CT you got all excited about because it has 500 miles EPA range may only deliver 100 - 200 when towing a trailer.

The actual size of the battery in CT is unknown as is the motor set up they will use. You should preface your conjecture with extrapolating from model 3.... besides the guys question was can he run his RV while charging. And the answer is can you find out what your RV load is? Then if your plug has 50 Amp rating subtract that load from the 50 amps and set CT charge rate no higher than that. Was that so hard?

 

[ajdelange]

The actual size of the battery in CT is unknown as is the motor set up they will use. You should preface your conjecture with extrapolating from model 3...

The actual size or the battery doesn't matter (much). This is an important concept people need to grasp. At the level of knowledge we have about CT consumption the best we can say is that they are going to pull about half a kWh per mile. I hope it's somewhat less than that. ABRP thinks it will be more. It isn't going to be half that and it isn't going to be double that.

You have clearly missed the essential concept which is, in words so you don't get a headache from having to deal with nasty numbers, that with a 14-50R set for maxium you are only going to pick up only about 14 miles (perhaps a bit more and perhaps a bit less) of range and that with a large trailer its going to be half or less than this.

. besides the guys question was can he run his RV while charging. And the answer is can you find out what your RV load is? Then if your plug has 50 Amp rating subtract that load from the 50 amps and set CT charge rate no higher than that. Was that so hard?

Before commenting on a thread I always encourage reading the posts in the thread. Saves the space wasted by repeating the same information in multiple posts.

 

[ajdelange]

I've written to the guy that makes the Electric Range Buddy suggesting that he modify it (trivial to do but he'd probably have to redo lab certification) to make it a load shedding device. Were he to do that he could probably sell them like hotcakes for various applications including this one. Were he to do this one would then plug the Buddy into the 14-50R and then plug the CT and RV into the Buddy's outlets and the vehicle would charge full bore until such time as the RV wants more than 50 A minus whatever charge level is set in the truck.

 

[Dids]

The actual size or the battery doesn't matter (much). This is an important concept people need to grasp. At the level of knowledge we have about CT consumption the best we can say is that they are going to pull about half a kWh per mile. I hope it's somewhat less than that. ABRP thinks it will be more. It isn't going to be half that and it isn't going to be double that.

You have clearly missed the essential concept which is, in words so you don't get a headache from having to deal with nasty numbers, that with a 14-50R set for maxium you are only going to pick up only about 14 miles (perhaps a bit more and perhaps a bit less) of range and that with a large trailer its going to be half or less than this.

Before commenting on a thread I always encourage reading the posts in the thread. Saves the space wasted by repeating the same information in multiple posts.

The only "facts" we have from Tesla is the mileage range projection.... and those aren't hard numbers. Since everything derives from those numbers it makes the size of the battery the driver in the estimations. I agree with you it is probably going to take ~500W/mile but it's a huge difference if it takes 400W or 600W. The difference between 140 miles vs 93 in 8 hrs of charging.

 

[ajdelange]

The only "facts" we have from Tesla is the mileage range projection.... and those aren't hard numbers.

That''s the story for now and from the advertised range and what we know about how Tesla builds cars we estimate about 500 wh/mi which, is an estimate of what the EPA rated consumption might be which charged at a 32A rate, comes out to a nominal 14 mi per hour.

it is probably going to take ~500W/mile but it's a huge difference if it takes 400W or 600W.

The thing is that it will take 400 somtimes and it will take 600 sometimes. If normal level terrain consumption is 500 nothing more than rain will take it up to 650 and even a wet road will take it up close to 600.

I agree with you it is probably going to take ~500W/mile but it's a huge difference if it takes 400W or 600W. The difference between 140 miles vs 93 in 8 hrs of charging.

Yes there is potential to get more or less range in 10 hours but while a 47 mile difference in possible range may seem like a "huge" difference to you it really isn't if you have a 150 mile run to the nearest supercharger before you on the morn.

Now this is without the trailer. A 14,000 lbs trailer is going to consume at least 500 Wh/mi on level terrain. Thus the mileage that can be added by charging at 7 kW is going to be less than 7000/ (500 + 500 ± 100) = 7 ± 1 miles per hour. In a 10 hour charging period that means as few as 60 miles and as many as 70 miles. I don't call that a huge range as it means you can't add enough charge in 10 hours to get to a SC 150 miles away.

Since everything derives from those numbers it makes the size of the battery the driver in the estimations.

As we have just gone through a set of calculations with regard to charging over night at a camp ground with out a single reference to the battery size it is pretty clear that the battery size has nothing to do with the question of the rate at which you can take on charge. Where battery size comes into play is where we look at how much battery we need to make the trip to the SC. If we assume the nominal 500 Wh/mi for the battery and 500 Wh/mi for the trailer that's 1 kWh/mi total and it's clear that to reach a SC 150 mi from the camp ground we are going to need 150 kWh. It should be clear that you will need a battery of at least 150 kWh capacity AND, whatever its capacity, it needs to be charged to at least 150 kWh. If you can charge for 10 hrs at 7 kw then you can add 70 kW hr and your battery had better have at least 80 kWh already in it IOW you must arrive at camp with 70 kWh charge on board. Note that even at this point we have not considered how big the battery actually is - only that it needs to be bigger than a certain size to tow a trailer that takes 500 wH/mi with a tractor that thales 500 Wh/mi.

Since we don't know what the actual consumption numbers will be for tractor or trailer the best we can do for now is use the nominal numbers. Our first job when we take delivery of the CT is to find out what our actual Wh/mi are. for various driving conditions. For most people it will be less than the EPA rated value but for some it will be greater. The next job is to find out what the consumption for the trailer is. Only then can we compute actual trips and charging rates. Until then the best we can do is the nominal numbers. If you understand what they are telling you you can gain a lot of insight. If you are hopeless with numbers then take some assurance in the fact that Tesla vehicles are equipped with software that tries to give you answers without your having to understand them.

 

[Dids]

That''s the story for now and from the advertised range and what we know about how Tesla builds cars we estimate about 500 wh/mi which, is an estimate of what the EPA rated consumption might be which charged at a 32A rate, comes out to a nominal 14 mi per hour.

The thing is that it will take 400 somtimes and it will take 600 sometimes. If normal level terrain consumption is 500 nothing more than rain will take it up to 650 and even a wet road will take it up close to 600.


Yes there is potential to get more or less range in 10 hours but while a 47 mile difference in possible range may seem like a "huge" difference to you it really isn't if you have a 150 mile run to the nearest supercharger before you on the morn.

Now this is without the trailer. A 14,000 lbs trailer is going to consume at least 500 Wh/mi on level terrain. Thus the mileage that can be added by charging at 7 kW is going to be less than 7000/ (500 + 500 ± 100) = 7 ± 1 miles per hour. In a 10 hour charging period that means as few as 60 miles and as many as 70 miles. I don't call that a huge range as it means you can't add enough charge in 10 hours to get to a SC 150 miles away.


As we have just gone through a set of calculations with regard to charging over night at a camp ground with out a single reference to the battery size it is pretty clear that the battery size has nothing to do with the question of the rate at which you can take on charge. Where battery size comes into play is where we look at how much battery we need to make the trip to the SC. If we assume the nominal 500 Wh/mi for the battery and 500 Wh/mi for the trailer that's 1 kWh/mi total and it's clear that to reach a SC 150 mi from the camp ground we are going to need 150 kWh. It should be clear that you will need a battery of at least 150 kWh capacity AND, whatever its capacity, it needs to be charged to at least 150 kWh. If you can charge for 10 hrs at 7 kw then you can add 70 kW hr and your battery had better have at least 80 kWh already in it IOW you must arrive at camp with 70 kWh charge on board. Note that even at this point we have not considered how big the battery actually is - only that it needs to be bigger than a certain size to tow a trailer that takes 500 wH/mi with a tractor that thales 500 Wh/mi.

Since we don't know what the actual consumption numbers will be for tractor or trailer the best we can do for now is use the nominal numbers. Our first job when we take delivery of the CT is to find out what our actual Wh/mi are. for various driving conditions. For most people it will be less than the EPA rated value but for some it will be greater. The next job is to find out what the consumption for the trailer is. Only then can we compute actual trips and charging rates. Until then the best we can do is the nominal numbers. If you understand what they are telling you you can gain a lot of insight. If you are hopeless with numbers then take some assurance in the fact that Tesla vehicles are equipped with software that tries to give you answers without your having to understand them.

You are still using the precise language of math to come to a guess. The problem I'm having isn't with the guessing or with the math. It's the misleading combination. The truth is you don't know what the average wattage per mile is for CT and yet you present your arguments as fact and make statements

The actual size or the battery doesn't matter (much)

Completely forgetting that the guess at the size of the battery and the projected range is how you came up with the guessed energy requirement.
People are using your responses to make decisions and from listening to you I have learned that CT will not be able to tow very far, that cameras don't work as well as mirrors, that FSD is not coming soon, and how long it will take to charge CT. Yet most of these things I learned are either misleading and in some cases just wrong.
In fact:
CT towing range will be much better than you think.
Properly implement cameras are much better than mirrors.
FSD 18 wheelers are already driving on public roads with no driver in vehicle.

 

[ajdelange]

You are still using the precise language of math to come to a guess.

Yes!!!

The problem I'm having isn't with the guessing or with the math. It's the misleading combination.

The problem you are having is that you are unaware of the existence of estimation theory, its interpretation and implications.

The truth is you don't know what the average wattage per mile is for CT and yet you present your arguments as fact and make statements.

I'm not presenting any arguments; just facts. If the battery charge at 7 kW and the Wh/mi is 500 then the rate is 7000/500 = 14. That's a statement of fact. If there is normally distributed uncertainty in the consumption of 50 (that means that the actual consumption is between 350 and 630) then there is a normally distributed uncertainty of 1.4 in the number of miles added per hour (meaning that the actual miles added are between 9.8 and 18.2 with 99.7% probability. That's a statment of fact. Precise mathematics is being used to estimate the chargning rate AND to quantify the uncertainty in that estimate. I wouldn't expect you to understand this unless you were trained in one of the sciences or engineering disciplines but I would hope that you would be able to comprehend that there are hundreds of thousands of people that use these techniques (some of which are hundreds of years old) every day. You might also be able to reason that since I used these techniques for an entire career without getting fired I probably know whereof I speak.

Completely forgetting that the guess at the size of the battery and the projected range is how you came up with the guessed energy requirement.

No, that is not how I came up with the consumption numbers. They were based on what I have observed from driving BEV and what ABRP thinks they might be. - more of the latter really.

People are using your responses to make decisions

Good! I hope I can help people to better understand what to expect. That's really what I am here for.

and from listening to you I have learned that CT will not be able to tow very far,

Great! You have learned something!

that cameras don't work as well as mirrors,

Your misunderstanding in that thread was based on your conception that light follows curved paths. What you should have learned from that thread was that light rays are not curved.

that FSD is not coming soon,

Yeah, I wouldn't hold my breath on that one.

and how long it will take to charge CT.

I hope so because the numbers I have given are pretty reasonable. Yet somehow I doubt you have really learned anything.

In fact:
CT towing range will be much better than you think.

What I would really like to know is why you think that. To make such an assertion you would have to reasoned differently than I have done and come up with more optimistic answers, PLEASE, PLEASE tell me how you got to that conclusion. Then we might have a meaningful dialogue.

Properly implement cameras are much better than mirrors.

As good as perhaps. Good enough that manufacturers want to use them. Close enough that regulatory agencies will permit them? Much better - no. Not at the level we could afford them in a car/truck and the user interface is a problem.

FSD 18 wheelers are already driving on public roads with no driver in vehicle.

Yes, there are some experimental driverless vehicles being tested under carefully restricted conditions. But there is no true (Level 5) FSD licensed for use in passenger vehicles on public roads and won't be for quite a while.

 

[Dids]

If

you are unaware of the existence of estimation theory

your conception that light follows curved paths

the numbers I have given are pretty reasonable.

If you assume a lot about someone else and don't read what they said then you can feel safe misleading people.
Estimation theory is based in empirical evidence. What empirical evidence do you have for CT? Did you even see one much less drive one? While it is possible that CT will require 500W/mi it is just as likely it will require 400w/mi average. I dont know and you don't either.
When you tell someone the will have a charge rate of 7kW you are being very generous to lose 680 watts per hour that's a lot of heat!
When you discuss towing you think energy = power. It does not. How energy is converted to power is huge. For instance if it takes 100 watts to spin a motor at 100rpm with 1 ft/lbs of torque.
100w=100x1
And another motor
100w=50rpm×2 ft/lbs
and then you add another pound to the load
100x2=200w
50x3=150w wow that's a 50 watt difference. It not magic yes the second motor top speed is slower but no one drives at 130 miles per hr in CT. What I'm trying to say is without Tesla giving us more information on the choice of power plant no one can know.

 

[ajdelange]

Estimation theory is based in empirical evidence.

In a word NO.

What empirical evidence do you have for CT?

I listed that in my last post.

Did you even see one much less drive one?

Yes, in the reveal video where I heard Elon say that it will weigh 3181 kg. I can put this together with observed data from another Tesla vehicle to come up with estimated Wh/mi consumption.

lWhile it is possible that CT will require 500W/mi it is just as likely it will require 400w/mi average.

Sure. That would be nice. It would only need a 200 kWh battery were that the case.

I dont know and you don't either.

Nope, and it doesn't matter as I have given you mean and standard deviation for the rate estimate. IOW the uncertainty has been accounted for. You ought to be able to figure out the implications of 400 vs 500 if you prefer 400.

When you tell someone the will have a charge rate of 7kW you are being very generous to lose 680 watts per hour that's a lot of heat!

Its not 680 watts per hour. The rate is constant at about 10% of what you take from the mains. That's not really a lot of heat at the 14-50R level. It's only 2320 BTU/h (0.2 ton). I gather you think that's an unreasonable number. In the last year in VA I've taken 1.95 MWh from the utility. 258 kWh went to heat and the rest to charge the battery, That's about 88% efficiency.

When you discuss towing you think energy = power.

Just use your head for a minute! I've had a commercial radio operators license since I was 12 and practiced electrical engineering for 50 years. What flight of fancy suggests to you that I would equate energy and power? You don't seem to understand the difference as evidenced by your conflation of an acceleration in energy consumption (watts per hour) with power (watts) above.

How energy is converted to power is huge.

What does that mean? Power is simply the first derivative of energy with respect to time. Or, if you plot energy vs time it is the slope of the line. If your electric meter reads 1000 kWh at the end of this month and 3000 kWh at the end of next you have used 1000 kWh of energy that month. A month of 30 days contains 30*24 hours so your average power consumption is 1000/(30*24) = 1.38 kW.

For instance if it takes 100 watts to spin a motor at 100rpm with 1 ft/lbs of torque.
100w=100x1

Nope again. One ft-lb of torque means that a lever 1 foot long would supply a force of 1 pound. In describing one rotation the end of that lever would travel 2*pi feet and thus deliver 1*2*pi foot pounds of work. At 100 rpm that 100*1*2*pi foot pounds per minute. A foot pound is 1.3358 joules and there are 60 seconds in a minute so the pwer delivered by the motor is 100*1.3558*1*2*pi/60 = 14.1979 Watts. If you had to feed the motor 100W to get that you would have an electric motor less efficient than a steam engine.

It not magic yes the second motor top speed is slower but no one drives at 130 miles per hr in CT. What I'm trying to say is without Tesla giving us more information on the choice of power plant no one can know.

I'm afraid that I have no idea what you are trying to say about motors. But we can draw several conclusions about them based on what we know. For example we know that the vehicle is going to use 24 kWh to go 60 mi if consumption turns out to be 400 wH/mi and 30 kWh if it takes 500 wH/mi. As it takes 1 hour to go 60 miles the power consumption will be 24 - 30 kW divided over 1, 2 or 3 motors. Now we can branch off into various interesting speculations as to the mix of motors as the PMSRM is more efficient than the IM.

 

[Dids]

In a word NO

Estimation theory is a branch of statistics that deals with estimating the values of parameters based on measured empirical data that has a random component. That's from wikipedia.

Its not 680 watts per hour.

32 A @ 240 V is 7680 W and in 1 hr it is exactly 680 Watts per hr.

Nope again

Instead of reading what I said you presume to educate me on the calculation. I bet its really hard for you to see a forest...
I also don't care what you did for living, how you were educated or how far you can pee.