Fair enough. I don't think he had his J1772 adapter either, which was probably the bigger miss.
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Fair enough. I don't think he had his J1772 adapter either, which was probably the bigger miss.
Canuck
Well-Known Member
Same here. I originally thought the UMC would be find and I'd just take it with me when I travel so I had a 14-50 outlet installed in my garage. But that became a hassle so I bought a HPWC. I don't need 80 amps at home so I just wired a plug into the HPWC and plugged it in at home. At my cabin, I have it wired directly to a 100 amp fuse for the full 80 amps so I can go there just for the day if I want.
In 15 months of ownership, I have never used it (except to demonstrate it once). But I do always carry it in the car. Then again, I do not travel much and when I have, I have used Superchargers and the occasional Level 2 charger.
JPP
Active Member
Your facts are close but not quite right. First there are two versions of Model S:
- the originals came with either a single or dual charger option and the dual charger was literally a second charger in the car. The single charger is capable of handling up to 40 amps, the dual up to 80 amps no matter where the power is coming from (i.e., UMC or HPWC).
- the newer cars all come with a single charger capable of handling either 48 amps (default) or 72 amps if you pay extra for the high amperage charger upgrade (which is a software unlock that can be added after getting the car if you desired...there is no physical hardware change).
Now let's talk wall connector. Since you live in Florida and use a UMC, presumably you are using the 14-50 connector which means the most you could be drawing is 40 amps assuming the 14-50 is wired per code on a 50 amp breaker (the breaker has to be 20% higher than the max current draw). So no matter which car you have, the most you can draw when charging at home is 40 amps. If you have an original car with the old style charger just the one, that is the max your car can draw and you are good to go. If on the other hand you have a new style car/charger, the max it can draw is 48 amps and you are actually charging 16% slower at home than you theoretically could because your car can charge faster than the outlet can provide.
If you install an HPWC, it is typically wired one of two ways -- either a 60 amp breaker (allowing a max sustained draw of 48 amps) or a 100 amp breaker (allowing a max sustained draw of 80 amps). Again, with a single car charger, you would either draw 40 or 48 amps depending on which era car your have. If it is the upgraded charger, you would either draw 48 amps (if the circuit was on a 60 amp breaker), or 72 or 80 amps (if the circuit was wired on a 100 amp breaker).
A couple of years ago, going with the UMC in a 14-50 breaker made a lot of sense because you didn't have to pay $750 for a HPWC and basically got the same charging rate unless you put dual chargers in your car. Some people even bought a second UMC (at $500) so they left one always plugged in at home and the second in the car). Now the HPWC costs $500 (or $550 if you get the 24' cable) which is the same price as a UMC. It can be wired for more current than a 14-50 breaker and the car can draw more/charge faster with the HPWC even if you get just the default charger.
Lastly is the issue of wear and tear. A 14-50 socket (which is fairly cheap -- under $30 at most hardware stores) is typically rated for so many "plug insertion/removal cycles). That's because their primary use is for laundry dryers, welding equipment and other items which are typically left plugged in. Basically, every time you plug it in and remove it, the contacts get pushed out a bit and you get a bit of metal fatigue (this is why old electric outlets are sometimes "loose" when you plug something in). When you are pushing high current (up to 40 amps in a 14-50 outlet), you want good, solid contact. Most electricians will tell you that if you are plugging in/removing the plug every day, you should plan on replacing the outlet every 1-2 years to be safe and ensure the receptacle is making good contact with the item being plugged in.
I realize this post was pretty long but wanted to lay out the facts for others who may be following this thread. Bottom line:
1. Assuming you buy a new Tesla and don't pay for the charger upgrade, your car can pull 48 amps. A properly wired HPWC will give you 50 amps on a 60 amp circuit and you don't need to pay for a 100 amp circuit unless you plan to buy a second car and run two HPWCs in master/slave load sharing mode. The HPWC will charge 16% faster than a 14-50 outlet on a 50 amp breaker.
2. If you have to wire a new charger/outlet into your charging location anyway, the cost differential between a 50 amp and 60 amp circuit is basically nothing (wiring a little thicker, different breaker).
3. You can't run a 14-50 outlet off a 60 amp breaker and comply with US electric code. It must be a 50 amp breaker
4. If you decide to go with a 14-50 outlet and your UMC and your daily charging solution, have an electrician check the outlet/receptacle and consider replacing it about every 18-24 months.
Whatever your solution, enjoy the fact you aren't going to gas stations anymore!
Canuck
Well-Known Member
dgpcolorado
high altitude member
Same. Even on a road trip it is difficult to come up with a scenario when I would need the UMC unless I know that I am planning to charge at a campground or my parents' house (dryer outlet). Around home my range greatly exceeds my local driving needs; even my 70 mile grocery shopping trips, with a large elevation change, are trivial in a Model S.
If something happens on a road trip to cause me to need a charge, then "plan B" is to find and use a J1772 public charge station. The UMC is "plan C". To remember to pack the UMC on a coming road trip I leave a note in front of my instrument cluster where I can't miss it. Old school but it works for me.
$550 for a spare UMC or WC is money I'd rather use for something else more useful.
Canuck
Well-Known Member
That's reason enough for me to get a spare one. I'd forget to put the note.
Also consider that the HPWC is much larger and more solid than the UMC. A lot of amps are going through the UMC and they have been known to fail, and if they do it might be after the warranty expires since wear happens over time. So it might not be that bad of an investment in the HPWC, or now called WC, but the HP part does make it much more heavy duty. I do agree it's not necessary for everyone though and the UMC is fine for home and travel.
dgpcolorado
high altitude member
I set my car to 32 A when I first got it, to reduce the strain/heat on the UMC. Speed of charging is pretty much irrelevant at home. Perhaps the UMC will fail and I will need a new one but I'm guessing that it will last until I trade in my current car on a newer one in a couple of years (I desperately want dual drive but can't afford it at current CPO prices).
Canuck
Well-Known Member
Good idea. My "classic" has dual 40 amp chargers and I have set my charge limit to 42 amps so that each charger only draws 21 amps for less wear on the chargers, which are liquid cooled. I couldn't do that with the UMC.
It would be interesting to know if the new chargers also split the load. You can tell with the old one because the car ramps up fast to 21 amps, then stops as it switches chargers, then ramps up to 42 (or if you put it to 50 it will ramp to 25 then stop and switch, -- whatever the number it splits it after 40).
CHG-ON
Still in love after all these miles
your post is informative but when you tell me I'm not factual I take issue with that
my facts are spot on FOR ME, I may not have covered all the base but read my post again, I said I do not have a dual charger, I currently have a '15 build pre 72 amp.
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My apologies. I was keying in on the part of your post that said:
In my mind, you were saying that spending money on the HPWC was unnecessarily and delivered not benefit. Clearly your second sentence is talking about your experience with your car and you correctly point out that in your case there is no difference in charging rate. I interpreted the first sentence to mean that you were saying that there was no benefit for new owners to get an HPWC. I apologize for the confusion.
For Canuck saying:
The UMC limitation actually comes from what you are plugging it into -- the 40 amp limitation comes from the circuit feeding the receptacle you are plugging it into (which is a 50 amp circuit breaker causing the 40 amp limitation). In response to your question
The new cars only have a single charger, there are no longer two physical chargers as the older cars could be upgraded to. That's why you can upgrade it after receiving the car (kind of like upgrading to EAP or FSD) -- it's a software thing.
Canuck
Well-Known Member
No - the UMC device itself is set not to put out more than 40 amps regardless of how many amps you feed it. The HPWC, now called WC, has dip switches so you can set how many amps it puts out, up to 80 maximum.
I stand corrected and learned something new! Thank you Canuck!
For others on the list, also found a rating on the 14-50 receptacles. They are rated for 1000 plug/unplug cycles. Assuming you do it once a day, that gets you about 2.5 years or so. That's why the electricians recommend replacing at about the 24 month point as a safety factor.
For others on the list, also found a rating on the 14-50 receptacles. They are rated for 1000 plug/unplug cycles. Assuming you do it once a day, that gets you about 2.5 years or so. That's why the electricians recommend replacing at about the 24 month point as a safety factor.
ElectricTundra
P85D AP1
A couple of quick thoughts on longevity (from running a lighting/audio/film production company).
- Receptacles like 14-50's don't last long when plugged/unplugged frequently and continuing to use them after they've become even slightly loose is a bad idea. It only takes a very minor bit of arc within the plug to render it useless. When the arc happens you hope you have a good breaker and an exceptionally good ground lest you can damage the equipment plugged in. Hot plugging makes this worse. Tesla doesn't use the neutral which greatly reduces downstream damage potential though some still exists. Keeping a UMC always plugged in and well secured to eliminate any strain or movement of the plug should be fairly OK I'd think.
- Cables can break down quickly, especially when carrying current near their limit. Every warm/cool cycle the cable goes through shortens it's life and that of the connections at either end as does each time it moves or changes its bend. Oversize is good, especially for SO types of cables like the UMC and HPWC. For me the larger cable of the HPWC and no receptacle worries was easily worth it.
- Receptacles like 14-50's don't last long when plugged/unplugged frequently and continuing to use them after they've become even slightly loose is a bad idea. It only takes a very minor bit of arc within the plug to render it useless. When the arc happens you hope you have a good breaker and an exceptionally good ground lest you can damage the equipment plugged in. Hot plugging makes this worse. Tesla doesn't use the neutral which greatly reduces downstream damage potential though some still exists. Keeping a UMC always plugged in and well secured to eliminate any strain or movement of the plug should be fairly OK I'd think.
- Cables can break down quickly, especially when carrying current near their limit. Every warm/cool cycle the cable goes through shortens it's life and that of the connections at either end as does each time it moves or changes its bend. Oversize is good, especially for SO types of cables like the UMC and HPWC. For me the larger cable of the HPWC and no receptacle worries was easily worth it.
hacer
Active Member
My state (Maryland) had an EVSE grant program that paid for half the cost (material + installation) of my HPWC. If I would have installed a 14-50 outlet it wouldn't have qualified for the program (it needs to be fixtured EVSE equipment). For me this meant it was cheaper to buy and install the HPWC than to install a 14-50 outlet. So now I have the benefit that I can charge at 48A when I want to (I usually set to 25 since it is slightly more efficient and its fine for overnight) and I can always keep my UMC kit in the car. Plus I saved money in the process, a win-win.
