What Wall Charger to Buy???

ajdelange

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I think you are misrepresenting the meaning of the word "average" as actually used in this discussion.
"Average" has a very specific meaning. It is one measure of the central value of a set of numbers. There is no disagreement about this. It is clear from this thread, however, that some people do not know how to interpret it and indeed one cannot really interpret it without also having a measure of central tendency (variance, standard deviation) or better yet, knowing the distribution or knowing that the populations being compared are at least similar.

Thus, for example, it might be reasonable to assume that drive length is Weibull distributed and use the mean to determine what percentage of the time charging would exceed x hours as a function of charge rate.
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HaulingAss

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I think it is less efficient, I’m just not sold on the magnitude here.

Would love to see some more solid numbers on this with someone measuring the actual wattage consumed.

Are you thinking like 5% less efficient? I could buy that, but it’s not saving me much money.
It's not always just about you. Transportation consumes around 30% of all our energy. If everyone is being told 120V charging works just fine for most people, that would add up to a lot of extra pollution or require a lot more solar panels and wind turbines be installed and maintained. Generally, it's best to just use the right tool for the job.

As to the magnitude of inefficiency of charging at 120 volts, it depends upon the specific temperature of the battery and how fast it's losing that heat to the ambient air. Neglecting temperature considerations, the average difference in efficiency is likely greater than 5% due to greatly increased vampire drain. A charging car never sleeps. On the otherhand, a car charged at 240 volts will likely only charge for an hour or two and immediately go to sleep when it's done charging instead of all night long while the temperature drops.

And in cooler weather the battery must be kept warm to charge to avoid slow, cumulative battery degradation. In non-tropical climates during the cooler months the higher charge current (like the 30-48 amps of most 240V charging) actually helps keep the battery at optimum temperature to avoid battery degradation over the life of the vehicle. Thi is because the DC current being supplied to the battery is only about 99% efficient and the other ~1% (or a little less) ends up as heat in the battery. This heat is beneficial when the ambient temperature during charging drops below 65 degrees F but at 120V and only 15 amps there is not enough of it to overcome heat loss to ambient.

The ideal battery temperature to avoid slow and cumulative degradation is around 70-80 degrees F although 10 or 15 degrees on either side is fine too.

If all the vehicle has is 120V @ 15 amps, you can have the situation where the car is circulating heat scavenged from the on-board electronics by the glycol solution and pumped through the battery to help it build a little heat. While charging at 120 volts, this pump will be running for hours (albeit at a slow speed). This is how the charging efficiencies accumulate to be significant, because 120 volt charging is so slow the inefficiencies happen over most of the time the car is parked. It's thousands of unnecessary hours per year. It's MUCH better to just let the damn car go to sleep.
 
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ajdelange

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The cost and difficulty differential between a 30a outlet and a 50a is astronomical.
I suppose that depends on one's definition of astronomical. The difference is in the wire. A 14-30 and 14-50 receptacle are going to cost nearly the same (as they are the same except for the ground pin) and a 50A breaker is typically about $4 more than a 30A breaker. 6 AWG THHN is $1.06/ft or so and 10 AWG is $0.38 and you'll need 3 pieces of each so a 50' run will be about $159 in #6 and $57 in #10. So $102 is astronomical?

Now when I pull No. 10 you may hear some bad language but when I pull No. 6 you will hear worse but it doesn't get really bad until we get to No. 4. So more horsefeathers and more bad info.

But it leads us to consider the option in which we say: "Hey, we're paying the electrician for the hairy knuckle work anyway. Might as well pay him a few hundred extra for the bigger circuit and be future proof".
 
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Crissa

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If I burn 80% of my range on Friday. The fact that I was able to charge 20% per day on Monday through Friday doesn’t help me get to the trailhead on Saturday.

There are many many cases where *average* use is irrelevant.

I think by nature trucks tend to be burstier in nature too. I don’t need a truck often during the week, but needing to drive significant miles in a truck on both days on the weekend is quite common.
Yes.

But that's still anecdotal. Which is why I argue against the word 'most', here. There's no evidence 'most' drive like that.

-Crissa

PS, @HaulingAss your argument about the cold doesn't really work here, since the inefficiency is creating heat, and that heat would stabilize the battery charging in the cold. A faster charging session would just waste time trying to pump amps into a non-warmed battery, too.

And @ajdelange the cost of upgrading wiring is not insignificant because material costs are not the only problem. Also, it needs four wires in the US, not three. Hot, hot, neutral, and ground.
 
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Ogre

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Yes.

But that's still anecdotal. Which is why I argue against the word 'most', here. There's no evidence 'most' drive like that.
I didn’t claim “Most” people drive any particular way. You did and continue to assert you know how ”most“ people drive.

Recommending someone installs a wall connector means you don’t have to predict how people drive. A wall connector or the UMC with 220v will satisfy the needs of 100% of owners. No need to try and guess what a persons usage will look like.

We know 120v is going to be a sub-par experience for a significant number of people. Particularly when we’re talking about the Cybertruck. Even among those where 120v will be “Okay”, the Wall Connector offers some marginal improvements.

It’s an easy recommendation. Nobody is going to buy one and regret waking up with 80% SOC every morning.
 
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SwampNut

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Also, it needs four wires in the US, not three. Hot, hot, neutral, and ground.
That's just not true, most things in the US do not need a neutral. I've never installed a Tesla plug with a neutral; worthless. You order the 10-30 plug from Tesla, three prongs. Some appliances need the neutral so that they can power 120v components, but most do not. I can't think of any shop tool, welder, motor, etc that needs the neutral.

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ajdelange

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I've explained this to you before and it's an established fact that you will use a lot less electricity if you charge near the top of the rated power for whatever charger your car has rather than from a regular 120v outlet and the reason why this is true has to do with the charging overhead that ajdelange mentioned in his previous post (his only good contribution).
I find it most amusing that you say this because the paragraph from my post from which you took it conflicts directly with what you are saying here. It is not an established fact that you will use more electricity if charging at a slower rate because it simply isn't true. It may be true that the charger is a few % less efficient at 120V input than at 240 but that would mean you would use a few % more wall kWh to get the same amount of battery kWh.

Furthermore the I did not mention "charging overhead". I mentioned "phantom drain" which is not charging overhead at all but in fact keep-alive overhead for the vehicle. Phantom drain is an ongoing thing. It happens when it happens (for example if you turn on the radio while sitting parked (i.e. vehicle in "P") or if TeslaFi asks for vehicle state in the middle of the night.

Your phantom drain bill must be paid at whatever rate you charge. But there is no premium on it if you pay it with a 120V configured charger or a 240. For example, if your phantom drain between charges has been 2880 W it will take you 2 hr to pay it back charging at 12A 120V but only a quarter of an hour to pay it back at 48A 240V. But you still have to pay back the full 2880W. You don't save any energy in either case.

I often wonder where some of these ideas come from. When I ask I never get an answer.
 

ajdelange

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That's just not true, most things in the US do not need a neutral.
What is this in respose to? What's just not true?

I've never installed a Tesla plug with a neutral;
] Me either. HPWC do not require neutral because they do not draw 0 sequence current.

useless[\QUOTE] Again you advertise your lack of familiarity with electrical systems. The neutral is there for a reason. It conducts 0 sequence (imbalance) current in any system which has it such as your house, your modern clothes dryer and, of course any tool or applicance (such as the many on my garage shelf) which do not differentially tap the phases.


You order the 10-30 plug from Tesla, three prongs.
Would we expect an appliance which does not require the neutral to use plugs that do? No but the UMC is not an appliance which does not require the neutral as it does require it for the 120V adapter. And includes it.
 

ajdelange

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As to the magnitude of inefficiency of charging at 120 volts, it depends upon the specific temperature of the battery and how fast it's losing that heat to the ambient air.
I'm afraid your reasoning is, once again, a bit off base here. When charged at a very slow rate the current going to the battery is small. Heat dissipated in the battery is proportional to the battery internal impedance and to the square of the charging current. Thus you will never have lower charging loss than when using the 120V adapter. And the loss has nothing to do with temperature difference. If charging current is I charging loss is I^2R where R is the real part of the battery impedance. Grossly simplifying if the thermal impedance of the battery to ambient remains constant over some range the teperature rise across the battery will remain about the same.

A charging car never sleeps.
Neither does a parked car which is not charging. The increase in phantom drain from a charging car is the software overhead required to supervise the charge and communicate the results to the app and monitoring programs, if any. Common sense says this is a very small additional burden,.
 

SwampNut

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Here’s my complaint about having a too big garage door. It’s expensive and unavailable. Then the HOA starts fining you because it’s boarded up for months after a drunk neighbor tore it off. And You can’t use it. The insurance balks at expediting it and at replacing it with a very expensive like door. Five months later the lawyers get involved.

But, otherwise, it’s fine.

I did a 70 amp circuit into my second garage for tools. Wire was free, and that’s enough for two tools at the same time. Or a CT in the future.
 


ajdelange

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You are right. I did not see the post (nor do I see ones from Ogre)??? I very seldom, if ever, ignore anyone and on the rare occasions I did so there used to be a flag indicating that that person had posted and the option to see the post was presented. That feature seems to be gone.

Anyway, no, 4 wires are not required if the connected appliance does not use the neutral and no, most EVSE do not use it.

Note also that my post said most of the difference was in the wire as the box, outletconduit and circuit breaker are all the same or nearly the same. I suppose you could argue that the electrician will require more hours to pull the heftier wire (or will charge you more in any case).

I will also add that whenever I have a 240V circuit pulled I always pull the neutral too. You do not know that you may, at some future time, want to replace that EVSE with some other appliance that does require the neutral.
 
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ajdelange

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I certainly have no complaints (but then I haven't done bigger than 9 x 9). These trucks don't seem to be getting any smaller. I guess the thing I like best about the new ones is their amazingly high R factors. 9 x 9 is a lot of square feet but its amazing how little heat goes through that 81 ft^2.
 
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ajdelange

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but in thermally controlled batteries, this isn't true. To have an effect it needs to produce more heat than the thermal management system can handle.
Yes, i believe it is true. Heat isn't the only way battery life is shortened. Ion interaction with the SEI is another. I am just looking at an articles describing a new battery claiming X cycles lifetime at a slow charge rate and Y < X at a faster one as verified at an independent testing laboratory. Although the article does not specifically say I would assume the two sets of tests were done with the battery temperature set at some standard value, wouldn't you? The test would be pretty meaningless if the runs were done at different temperatures.
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