blodg1
Member
In that case, just get the cheapest J1772 charger you can find. Longer cable is usually better depending on the mounting location. I installed one at work and that is where I do 99% of my charging.
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40 mi commute, office charger debate
- Thread starter LibertyEV
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Rough estimate of 80 miles per day X 5 days per week = 400 miles per week. 400 miles divided by 3.7 miles per kWh (could be a bit higher or lower) = 108 kWh. Assuming $0.1056 per kWh (10.6 cents per kWh) the commute would use approximately $11.40 per week in electricity. Over a year that is almost $600. That is approximately how much you would save by only charging at work during the week and charging at home only on the weekend as needed. That's how I would do it.
Check with the local electric utility for any rebate programs for businesses that install EV charging equipment.
Electricity Rates in the United States (December 2021) – Electric Choice
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Most cheaper ($500ish and below) chargers use plugs (14-50 or 6-50).
I would just get a 14-50 connection and use the mobile charger. No need to spend money on a separate wall charger.
A 14-50 receptacle would not last long when subjected to daily plugging and unplugging when you take the Mobile Connector with you as you leave work. In this scenario you want a charging solution that will last and perform in all weather conditions for the long term. That means a hard wired installation. The cost of installing a circuit with a 50 amp GFCI circuit breaker, quality14-50 receptacle + Mobile Connector and 14-50 plug adapter would equal or exceed the cost of the Tesla Wall Connector.
Depending on your cost per kWh, it could take 1.5 years to recoup the cost of a wall connector. Less if your kWh cost at home is more expensive.
Who is to say another person doesn’t use your charger?
I know I'm late to the party. But the kW-hr and Joules debate always pops up.
One more time on this: If one has a gallon of water, that's an amount.
If one pours out the water over fifteen seconds, then the rate that water is being removed is 0.25 Gallons/minute.
Energy works the same way. The amount of energy is in Joules. A kilogram of coal, when burned with oxygen (C+O2 -> C02 + heat), gives off energy; about 30x10^6 (30 MJ). A power plant pays $$ for a ton of coal, burns it to extract the heat energy, then converts the heat energy into electrical energy.
The rate that one converts or uses energy is, in SI units, Watts; and One Watt = a rate of One Joule per second. That 100 W lightbulb in the ceiling is, yes, using 100 Joules per second of energy, and that translates right back to the amount of coal (or whatever) the power company is buying to provide that energy. And, yeah, they buy coal in so-much-bucks-per-ton.
As others have mentioned, all of this makes a lot more sense if one plays with Joules, Watts, Megawatts, and/or Megajoules. But somewhere along the line power companies started charging for energy in units of kW-hours. So, yeah, around here, turn on ten 100 W lightbulbs, wait an hour, then flip the power company $0.15.
But it also shows up in battery sizes. You buy a Tesla, say it comes with a 75 kW-hr battery. That's how much energy it can store. Connect it to a 10 kW source, and, in theory, one can charge the car in (75 kW-hr)/(10 kW) = 7.5 hours. Connect it to a Supercharger that can do 250 kW and, if one didn't care about the health of the battery getting charged that fast at high levels of charge, one could charge the car in (75 kW-hr)/(250 kW) = 0.3 hr, or 18 minutes. (In reality, the rate of charge slows down above 30% state of charge or so, so it takes more like an hour or so to take a Tesla from dead empty to 100% full, but I digress.)
So, keep your units straight. You'll be happier, your calculator will be happier, and you'll stop annoying the pundits.
(There was a Tesla forum I used to be on where a particular troll used to mess up these units, on purpose, just to confuse newbies. Don't you be that troll.)
Finally: As regards the charging station. If you end up paying for the electricity, then don't bother, you can charge at home. It'll be more convenient since you won't have to keep on moving the car out of the charging stall so other people can get in. Very roughly, ye Bog Standard J1772 cheapie has 32A at 240V, for a charge rate of 7.68 kW. Your M3 gets around 0.25 kW-hr/mile (Notice! Units of Energy Per Mile!), so a 40 mile trip uses around 10 kW-hr of energy. Time to charge that amount would be 10 kW-hr/7.68 kW = 1.3 hours, at which point you'll have to leave your office, move the car, and let somebody else in. Which might be a bit of a pain on rainy days.
At home, if you've got a TWC hooked to 240 VAC and a 60A circuit, that charges at 45 MoCpH (Miles of Charge per Hour) at 11.52 kW. A round trip of 80 miles would use 20 kW-hr, so you're talking a little under two hours to get the car back to where it started. You gotta sleep sometime, so do it at home.
Alternatively: Say that work decides to provide the electricity for free. So, 80 miles a day -> 20 kW-hr; say you get charged $0.18/kW-hr, so that's $3.60 a day of electricity cost that you'd be avoiding. That might make it worth getting rained or snowed upon, your call. My son, who lives in California and has an M3, gets that perk and doesn't have a charger at his place for that reason.
At my place of work the company's put in a couple of Chargepoint stations that can deliver 28A at 208 VAC, but they charge $0.40 an hour to use it for employees. Others who happen upon the spot get charged $0.50/hour. The rate is 5.824 kW; so they're charging $0.40/hour * 1/(5.824 kW) = $0.0687/kW-hr. Which ain't bad. But I've got Home Solar, so my electric costs are near-zero, so, again, I don't bother.
Good luck!
One more time on this: If one has a gallon of water, that's an amount.
If one pours out the water over fifteen seconds, then the rate that water is being removed is 0.25 Gallons/minute.
Energy works the same way. The amount of energy is in Joules. A kilogram of coal, when burned with oxygen (C+O2 -> C02 + heat), gives off energy; about 30x10^6 (30 MJ). A power plant pays $$ for a ton of coal, burns it to extract the heat energy, then converts the heat energy into electrical energy.
The rate that one converts or uses energy is, in SI units, Watts; and One Watt = a rate of One Joule per second. That 100 W lightbulb in the ceiling is, yes, using 100 Joules per second of energy, and that translates right back to the amount of coal (or whatever) the power company is buying to provide that energy. And, yeah, they buy coal in so-much-bucks-per-ton.
As others have mentioned, all of this makes a lot more sense if one plays with Joules, Watts, Megawatts, and/or Megajoules. But somewhere along the line power companies started charging for energy in units of kW-hours. So, yeah, around here, turn on ten 100 W lightbulbs, wait an hour, then flip the power company $0.15.
But it also shows up in battery sizes. You buy a Tesla, say it comes with a 75 kW-hr battery. That's how much energy it can store. Connect it to a 10 kW source, and, in theory, one can charge the car in (75 kW-hr)/(10 kW) = 7.5 hours. Connect it to a Supercharger that can do 250 kW and, if one didn't care about the health of the battery getting charged that fast at high levels of charge, one could charge the car in (75 kW-hr)/(250 kW) = 0.3 hr, or 18 minutes. (In reality, the rate of charge slows down above 30% state of charge or so, so it takes more like an hour or so to take a Tesla from dead empty to 100% full, but I digress.)
So, keep your units straight. You'll be happier, your calculator will be happier, and you'll stop annoying the pundits.
(There was a Tesla forum I used to be on where a particular troll used to mess up these units, on purpose, just to confuse newbies. Don't you be that troll.)
Finally: As regards the charging station. If you end up paying for the electricity, then don't bother, you can charge at home. It'll be more convenient since you won't have to keep on moving the car out of the charging stall so other people can get in. Very roughly, ye Bog Standard J1772 cheapie has 32A at 240V, for a charge rate of 7.68 kW. Your M3 gets around 0.25 kW-hr/mile (Notice! Units of Energy Per Mile!), so a 40 mile trip uses around 10 kW-hr of energy. Time to charge that amount would be 10 kW-hr/7.68 kW = 1.3 hours, at which point you'll have to leave your office, move the car, and let somebody else in. Which might be a bit of a pain on rainy days.
At home, if you've got a TWC hooked to 240 VAC and a 60A circuit, that charges at 45 MoCpH (Miles of Charge per Hour) at 11.52 kW. A round trip of 80 miles would use 20 kW-hr, so you're talking a little under two hours to get the car back to where it started. You gotta sleep sometime, so do it at home.
Alternatively: Say that work decides to provide the electricity for free. So, 80 miles a day -> 20 kW-hr; say you get charged $0.18/kW-hr, so that's $3.60 a day of electricity cost that you'd be avoiding. That might make it worth getting rained or snowed upon, your call. My son, who lives in California and has an M3, gets that perk and doesn't have a charger at his place for that reason.
At my place of work the company's put in a couple of Chargepoint stations that can deliver 28A at 208 VAC, but they charge $0.40 an hour to use it for employees. Others who happen upon the spot get charged $0.50/hour. The rate is 5.824 kW; so they're charging $0.40/hour * 1/(5.824 kW) = $0.0687/kW-hr. Which ain't bad. But I've got Home Solar, so my electric costs are near-zero, so, again, I don't bother.
Good luck!
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I don’t understand what all the fuss is about. It’s an 80 mile commute for heaven’s sake. Charge at home in the evening to 80-90% and you are more than good to go. No need to charge at work unless you need to feel special.
With the price of the HPWC now $400, the savings going to a 14-50 is very small(outlet is 50-100, extra neutral wire that the HPWC doesn't want or need, and GFCI outlet is $150-$200 and may actually be more for a commercial setting). Additionally, since you barely need more than a 120V outlet for your needs, yo could have them wire up a 16 or 24 amp circuit and save on wiring costs.
Note also I think you misunderstood my question about who will be charging there. It wasn't really a "is there more than one tesla there", but rather a "If some rando off the street decides to plug in their Bolt over the weekend, will that be okay with the company"
Note also I think you misunderstood my question about who will be charging there. It wasn't really a "is there more than one tesla there", but rather a "If some rando off the street decides to plug in their Bolt over the weekend, will that be okay with the company"
For the free L2 chargers at my work it requires an RFiD card that is only issued to employees and prevents unauthorized public use. I believe some charging stations can be set up with passcodes but RFID cards would be better for tracking and auditing as opposed to a passcode that is easily shared online.
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ATPMSD
Active Member
From the manual
“Warning: Do not use the Mobile Connector when either you, the vehicle or the Mobile Connector is exposed to severe rain, snow, electrical storm or other inclement weather.”
So while the outlet may be weather rated the Tesla connector is not. Your call of course.
All excellent points. Thank you everyone for weighing in. I’ve done a little research. It only cost $0.09/kWh. I won’t pay this at work but I will at home.
I think if I decide to do anything I may consider a wall connector since its weather tolerant. At $400 now, it’s even more affordable than the wall connector I bought when I purchased my MY at $550.
Someone mentioned you can set it up to only charge selected vehicles. I’ll have to look into that. Don’t want to put the office out by creating a line of EV’s while I’m not there
I think if I decide to do anything I may consider a wall connector since its weather tolerant. At $400 now, it’s even more affordable than the wall connector I bought when I purchased my MY at $550.
Someone mentioned you can set it up to only charge selected vehicles. I’ll have to look into that. Don’t want to put the office out by creating a line of EV’s while I’m not there
ATPMSD
Active Member
When you commission the unit that option is near the bottom of the page.
Johnny Vector
Member
By the way, since we're trying to be correct here, a mJ is a millijoule, 1/1000 of a joule. A megajoule is written MJ, with a capital M.
NIST has a lovely set of pages about SI units. Here's the one about prefixes! Poke around those pages to learn more about things like power and energy.
I did not own a Tesla at the time, so I was not aware of the specifics of the Tesla mobile charger. Now that I have my Tesla, I have no need to charge at work (which is about 30 miles each way).
sleepydoc
Well-Known Member
That was my thought, but on second thought, if work is paying for it, I’d just charge at work and skip charging at home completely!
24/7/365 = 0.00939. Not sure what’s so difficult about that!Technially correct of course, 7 kW is a unit of time but a lot of people miss that. So while 7 kW / hour is redundant, it gets the point accross to the not yet savvy.
What really kills me is 24/7/365!!!
Many times when you look at the utility bill you see a cost per kWh, i.e. $0.09 and assume you are done when that charge is only for power generation. In most cases there are additional charges, taxes and fees on each bill. The most common charge is the delivery charge (covers the cost of delivering power to your home, power line maintenance and other infrastructure costs.) The delivery charge is often within 1 cent of the power generation charge (per kWh.) One way to assess your total cost per kWh is to divide the total current amount due by the total kWh consumed. You will probably find that your total cost per kWh is in the range of $0.14 per kWh.
Example: $100 (total amount due per the utility bill) / 700 kWh (amount consumed for the current billing period) = $0.14 per kWh.
Thanks for jumping in and clarifying for everyone. I got confused with kW/kWh being lowercase and forgot that mega is capital M. My mistake!
Ciaopec
Active Member
To avoid the endless confusion, we can agree to use horsepower for power, and ft-lbs for energy... no units of time anywhere in these
By that warning, "you" yourself are also not weather rated to stand outside according to Tesla
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