Forums

Charging at work- J1772 vs Tesla equipment

Charging at work- J1772 vs Tesla equipment

At work there are about a dozen charging stations, all are J1772. Right now I can use the J1772/Tesla adapter to charge my M3 model SR+ but the highest charging rate at 208vac is 30 amps.

Is there a good argument I could use to convince Management to consider upgrading the J1772 to Tesla charging equipment? There are other EVs at work that share the charging facilities; M3 LR, Model S, and other makes and models; Leaf, Bolt, Volt, CMax, even a Fiat EV, not to mention plug in hybrids.

If a couple of J1772 stations were converted to Tesla charging stations, would that improve Tesla recharge time? If so, that may be a good argument for upgrading a couple of J1772s.

stevenmaifert | August 11, 2019

It's not the charging station, it's the available electrical service to the charger. If all your workplace has available is 3 phase 208V commercial AC service limited to 30A, installing a Tesla Destination Charger (HPWC) is not going to make any difference. Be thankful your employer has gone the extra mile for workplace charging, and I'm going to assume you get to charge for free?

johncrab | August 11, 2019

It depends on the circuit which is available. Three phase is better than split phase but distance to the transformer, transformer load and line length are all going to be factors. Three phase is inherently balanced and the power factor of a Tesla is .98, I believe (no idea about other makes but I would assume something close). There is also a concern about how much of a load building management wants to drop on that circuit average or max and cost factors such as peak demand, etc., and that gets a bit crazy with commercial services. There is a good chance a HPWC would offer better charging rates for Tesla owners than the Level 2 but then Tesla owners would be fighting over them or in the best case, politely disconnecting so others could use them. So the place to start is with building management and see if they have any load concerns. If not they might be good allies in getting a couple of HPWCs installed in the name of going green, etc. What they are likely to say though is that the J1772 can be used by anybody and it's a lowest common denominator solution. Worth a try though. Play up the cool tracing green light. Management always like cool, shiny things that light up.

Yodrak. | August 11, 2019

"... the highest charging rate at 208vac is 30 amps."

That's not adequate to cover what you need for your commute? I only need half a work day of charging at the conditions you specify to cover my round-trip commute.

You're not expecting your employer to provide for all your charging needs, are you?

kaffine | August 11, 2019

johncrab: Split phase would actually be better for charging. Split phase is 240V while 3 phase is normally 208V so you would charge slightly faster with split\single phase than 3 phase.

If they are limiting it to 30 amps that is likely what the wire supports so swapping them over the Tesla WC would have the same limit but now only Tesla can use those to charge unless one of the other EV has an adapter to use a Tesla WC. Now they may have oversized the wire or be able to replace the wire easily to increase the power available assuming they have the extra capacity.

If they are getting that much use the better argument to make would be to install more EV chargers. I'm not sure if Tesla still offers the WC for companies to install for reduced cost or no if they do that might be a way to convince them to install Tesla WC. I would say they are better off staying with the J1772 standard. This way they don't have Tesla only spots and the some that other brands and Tesla can use.

blakamp | August 12, 2019

You likely have to get your company to first install a higher amperage line and breaker to something like 100a to support an 80a charger (19.2kW, roughly 60mi/hr). There are chargers like Wattzilla that have 2 or 4 heads which can (obviously) share the power, but also intelligently charge on side as fast as possible, until another vehicle shows up. In those scenarios, getting users to move their vehicles when fully charged becomes the next challenge.

milesbb | August 12, 2019

You are lucky to work for a company that is offering this benefit. As the number of employee EV cars increase, most being Teslas, they will likely be adding more charging stations. If they have 480 volt three phase power, which is very likely, A very economical way for them to add up to 12 stations is to run a 100 amp 480/277 circuit. Each of the three phases in this circuit can power 4 HPWC in load share mode, 12 HPWC total. For the person that get to work first they could get up to 80 amps at 277 volts. As charing stations fill up the available charging current will drop to 20 amps. Available charging current will rise again as some cars get fully charge and drop their charging current. The last workers to leave can get the full 80 amps.

Earl and Nagin ... | August 12, 2019

One consideration is whether your company pays more for afternoon electricity than morning electricity. If they do pay more in the afternoon, it is important that all charging be completed by the time the rates increase. If this means they need chargers that are faster, you can make that case for Tesla HPWC OR higher power J-1772.
Since most commuting is less than 48 miles, however, even 16 amp/208 volt (~12 mph) charging is sufficient to charge by noon, however.

Lonestar10_1999 | August 12, 2019

Thanks for all the info. I know Tesla has a destination charging program where Tesla provides free charging equipment but the recipient business is responsible for installation and ongoing maintenance. So I was wondering if the existing transformer which has a 3 phase 208/120 v secondary would be able to charge up a Tesla at a higher rate than a J1772.

I do feel fortunate that the company allows employees to charge for free. The challenge is to maximize throughput so the benefit is not resource constrained and is available to all employees who wish to partake.

Yodrak. | August 12, 2019

Companies that want to hire the 'best' employees offer many kinds of perks, including various kinds of perks to subsidize commuting costs especially if the subsidies can also contribute to a reputation of being pro environment. For example, they may subsidize the cost of using public transportation or car pooling, and now also offer free or low cost EV charging. However, employers do not particularly feel inclined to extend the perks beyond commuting to work. They are not inclined to provide sufficient fuel to cover all of an employee's transportation costs by providing, in effect, unlimited free charging. 5-6 kW is an adequate charging rate to provide for employee's commuting needs.

reed_lewis | August 13, 2019

As others have said, at that rate in 8 hours, you can get over 45 kWh of power. That is sufficient to drive a pretty long distance. If you needs are higher than that, then you are driving too far.

And even if they put in Tesla plugs instead of J-1772 plugs, it is the circuit breaker that typically determines the amount of power available. Where I work, we have commercial power, and it is 24 amps, which means I only get 5 kW of power. Also if the ports are chargepoints (which they are at my office), they can control how long you stay connected. My office's garage allows 4.5 hours of free charging and then after that charges you $2.50 per hour you stay connected. I feel that getting 20 kWh (worth about $2.50 for me at the price I pay at home is quite fair.

geo.teepe | August 13, 2019

How many miles range do you get per hour charging time?

reed_lewis | August 13, 2019

I always have my meters and quote everything in kW because that is more accurate. Using the number of 5 kW, it would take 15 hours to completely charge from 0-100 at my office (which of course I never have to do).

MPH charging speed is an estimate. kW is a real number.

jimglas | August 13, 2019

"MPH charging speed is an estimate. kW is a real number"
True, but most of us are simple and mph is also simple.

Lonestar10_1999 | August 13, 2019

I am not sure what the circuit breaker protection they have at work but my SR+ pulls 30A at 208v which translates to approximately 25 miles per hour recharge rate.

When I charge at home, it’s a Nema 14-50 receptacle supplying 240v. The SR+ is able to receive the max 32A. Of course with the generous free charging perk at work I almost never change at home.

I imagine that if Tesla would supply free charging equipment to my company under the destination charger program, the charging rate would be enhanced slightly if at all. It would also inconvenience several coworkers who drive non-Tesla EVs.

I think the path forward is to learn to share the company’s J1772 charging equipment as best we can.