Charging in RV parks

[ajdelange]

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.

Yes I know what it is. I did it for 30 years. You can look it up in Wikipedia but if you don't know what those words mean you are not qualified to draw conclusions and publish them as facts. Based on your last post I would have to conclude that you think I can't do an estimate on any CT parameter unless I have made a measurements on a CT. Not so. As long as I have a model (and it doesn't have to be perfect nor in fact is it in general perfect) I can compute estimates. In this case the model comes for other Tesla vehicles.

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

Statements like this only show that you do not have even the most fundamental understanding of electrical energy and should probably refrain from presenting yourself as someone who does. Energy is measured in Joules or Watt-seconds or watt-hpurs. (3600 Joules). Power is the rare of flow of energy and is measured in Joules per second. (Watts) or Watt-hours per hour (Watts). 680 watts per hour means that the power draw is increasing or decreasing 11.3 watts per minute. If 32 A is being drawn from a 240V supply the power drawn is not increasing or decreasing. It is constant. I expect what you are trying to say is that if you are drawing 7680 from the mains and I say only 7000 are going to the battery then 680 are going elsewhere to heat and that's true. But it is 680 watts - same units as the units of power drawn from the mains. In one hour that loss amounts to 680 WATT HOURS. Not watts per hour.

Instead of reading what I said you presume to educate me on the calculation.

You made it clear that you needed it. Let's have a look at what you wrote:

How energy is converted to power is huge.

I read and reread that. My language is English. That sentence means nothing to me in English.

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

This is dead wrong demonstrating that you needed education on how to calculate power from motor speed, torque and power. So I showed you how to make that calculation. I doubt I educated you though.

I also don't care what you did for living, how you were educated

Well you should if you don't want to continue to look the fool. You are trying to assert yourself as an authority on something you clearly know very little about. You have demonstrated this time and time again. The smart man would say "Gee, this guy did electrical engineering for 50 years. Maybe he knows something about it. Maybe I should look up "Watt per hour" on the web before I challenge him on this" (you wouldn't find it - that should be a clue).

or how far you can pee.

Well I'm 75 so afraid I'm not going to be very impressive in that department.

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[Dids]

Yes I know what it is. I did it for 30 years. You can look it up in Wikipedia but if you don't know what those words mean you are not qualified to draw conclusions and publish them as facts. Based on your last post I would have to conclude that you think I can't do an estimate on any CT parameter unless I have made a measurements on a CT. Not so. As long as I have a model (and it doesn't have to be perfect nor in fact is it in general perfect) I can compute estimates. In this case the model comes for other Tesla vehicles.

Statements like this only show that you do not have even the most fundamental understanding of electrical energy and should probably refrain from presenting yourself as someone who does. Energy is measured in Joules or Watt-seconds or watt-hpurs. (3600 Joules). Power is the rare of flow of energy and is measured in Joules per second. (Watts) or Watt-hours per hour (Watts). 680 watts per hour means that the power draw is increasing or decreasing 11.3 watts per minute. If 32 A is being drawn from a 240V supply the power drawn is not increasing or decreasing. It is constant. I expect what you are trying to say is that if you are drawing 7680 from the mains and I say only 7000 are going to the battery then 680 are going elsewhere to heat and that's true. But it is 680 watts - same units as the units of power drawn from the mains. In one hour that loss amounts to 680 WATT HOURS. Not watts per hour.


You made it clear that you needed it. Let's have a look at what you wrote:
I read and reread that. My language is English. That sentence means nothing to me in English.

This is dead wrong demonstrating that you needed education on how to calculate power from motor speed, torque and power. So I showed you how to make that calculation. I doubt I educated you though.


Well you should if you don't want to continue to look the fool. You are trying to assert yourself as an authority on something you clearly know very little about. You have demonstrated this time and time again. The smart man would say "Gee, this guy did electrical engineering for 50 years. Maybe he knows something about it. Maybe I should look up "Watt per hour" on the web before I challenge him on this" (you wouldn't find it - that should be a clue).


Well I'm 75 so afraid I'm not going to be very impres

sive in that department.

 

[Cyber_Dav]

Let's rename this thread to "aj and Dids go at it. Again." /s

 

[ajdelange]

Now he wants us all to know that he doesn't understand the difference between watt-hour and watts per hour. Sorry guys. I put him on "ignore" status.

 

[Dids]

? that's because it's the same thing, no let me use the exact word " equivalent ".

 

[Bathbunny]

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.



.

 

[Bathbunny]

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 14-50 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.

Why are we assuming that the CT will have the same old charger on board as the current Teslas? The trimotor is likely to have twice the battery capacity. Even if Tesla revived the dual chargers used on older LR Model S (and the 1st-gen HPWC), we would get 96A at 240V and so take at least 10hrs to charge the trimotor (assuming a 200KWh battery) from near empty to full.
Moreover, if the CT will feature V2G, it is likely to have something more sophisticated on board and Tesla will have some type of new wall charger/controller for it.
None of that will affect calculations for campgrounds, but I'd guess that the mobility charger included with the vehicle should be able to use at least the full power of a 14/50 outlet, i.e., 40A, not just 32A as in all models to date.

 

[ajdelange]

As to the chargers: 24 A modules are very convenient in that one can be used for each phase. Thus the latest charger, that in the Y, has 3 of these modules in cars destined for Europe and 2 for cars destined for the US. It is, therefore, probable that the CT will use that same charger philosophy. While there is no guarantee that Tesla will continue with this 24 A modue approach in the future it does seem more likely that they will rather than come up with a new one. If they want to increase the charging rate of the TriMotor it seems likely that they would install a second port connected to a second 2 module charger as this is the approach they have apparently taken with the Semi.

The CT will not have V2G in all liklihood but that doesn't mean that the internal architecture of the current charger is not capable of being used as an inverter as well as a rectifier. 240 VAC in the bed has been promised and the model Y charger architecture could be be used to supply it.

The full "power" of a NEMA 14-50 is 50 A. Code requires that EVSE be derated to 80% so the maximum EVSE can draw from a 50 A circuit is 40A. But there is an exception in the code that says that a 14-50R can be wired to a 40 A circuit as well as a 50 A one. The maximum that EVSE can take from a 40 A circuit is 32. Thus the lawyers have told the engineers that they need to limit the current the UMC can allow to 32 A. That's where that limitation comes from and I think we can be pretty sure that the UMC that comes with the CT will have it too.

 

[ajdelange]

Did you mean "adding an EV charger" ? If so I doubt it as the campgrounds already have good charging for BEVs via the 14-50R's. OTOH Tesla used to (and for all I know still does) supply free HPWC to businesses and gives them an allowance for installation.

 

[Dids]

Which part of the 3 motor CT specs is 1/2 ton? They look more in line 3/4 ton trucks.

 

[ajdelange]

Roger that. Obviously I thought it was a Spoonerism of the fingers. I guess I think it would be entirely fair to charge for that electricity. Of course not charging for it would put the operator who doesn't at a competitive advantage. Quite a few hotels/motels etc. provide destination charging for their BEV driving guests. Places with destination chargers get listed on Plug Share. Very few charge for their use and the ones that do get flagged in the comments with things like "Don't stop here. $5 charge". The market will work it out.


That's a decision you will have to make for yourself. It's not designed to pull more that 14,000 lbs so if you are contemplating a trailer bigger than that then clearly no, the CT isn't for you. But it is interesting to look at what it can do at the 14,000 design limit.

The time it takes a vehicle to reach a given speed is proportional to its mass. The CT does 0 - 60 in 2.9 sec. Assuming its weight to be 2700 kg then the 0 - 60 time while towing a 14000 pound trailer is
2.9*(2700+ 14000/2.2)/2700 = 9.7 seconds. That's pretty impressive as far as I am concerned.

A 0 - 60 time of 2.9 seconds assuming uniform acceleration (at the torque limit) up to that speed implies that the motors can deliver 666 kW (893 HP). Were all that power being used to increase the rigs gravitational potential energy the vertical speed would be
666000/(9.8*((2700+ 14000/2.2)) = 7.5 m/s. Sixty mph is 28.8 m/s so 7.5 m/s at 60 mph corresponds to a 26% grade! The potential energy load going up a hill isn't the only load, of course, but clearly grades of 5 to 10% should be a breeze,

Now of course the dead horse in the room is range. You may be able to accelerate fast and go up hills like the wind but both of those activities use energy and you don't get it all back. So your proactical range which starts at 400 miles with no trailer may wind up at 200 or less. Were I considering such things (I'm not - my towing is limited to a half mile tow from boat shed to ramp in the spring and the return trip in the fall) it is the range that would drive my decision. Other than that I'm guessing, without any first hand experience) that the CT will stand up pretty well next to the big ice trucks.

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