Installing a 30A home charger

Installing a 30A home charger

I am considering installing a 30A home wall charger in preparation of next year's Model S arrival in the UK. I have a choice of J1772 or Type 2 connectors, not sure what the difference is between these two.

My question is, what sort of charging 'miles per hour' can I expect from a 30A charging box, and is it worth getting the Tesla HPWC instead? What does the Tesla charging box do above a 30A box?

kw1 | May 17, 2013

Charging boxes are derated to 80% for continuous power - which is what happens when you charge. So in the US a 50 amp rated circuit charges at 40 amps continuous. This is the standard NEMA 14-50 plug in the US which gives about 30 miles per hour of charge. A 30 amp circuit actually charges at 24 amps continuous which is about 18 miles per hour of charge.

The HPWC can go to 100 amps (80 amps continuous) which is about 60 miles per hour of charge, but to achieve this rate you need to order your MS with the "twin chargers" option. If you order the MS with the single on-board charger you are limited to a maximum of 31 miles per hour of charge as this is the maximum a single on-board charger can handle.

I have the single on-board charger with a 50 amp NEMA 14-50 plug in the garage and this is more than adequate for my needs. I rarely drive 250 miles in a day but even if I did the car would be fully charged from zero overnight. Note that "supercharging" bypasses the on-board charging circuits completely, going direct to the battery, and I have charged at a "supercharger" station at rates well above 150 miles per hour of charge.

dborn | May 17, 2013

Amps x volts equals watts. Ideally 30 x 220 gives 6600 watts or approx 6.5 kilowatts per hour less derating. Europe is likely to get 3 phase charging - some of us here in Australia can get this as well ( me included). . Not sure about the UK. Suggest you speak to an electrician about what is possible for a domestic supply in the UK. I don't think it is going to be comparable to what they get in the USA.
3 phase probably means you need nothing else - more than enough juice to charge up. Here we can also get single phase 32 amp at 240 volts. Just need appropriate sized wire and plug/ sockets. Roughly 7.5 kw less derating. 3 phase is much higher voltage with amps around 32 here as well. As I said, not sure how this will work with the car. I don't think it has been announced.

kw1 | May 17, 2013

Thanks dborn, My above comments were all for 240 volts, 3-wire single phase, which is common in the US for residential construction.

scoops | May 17, 2013

It's all quite confusing!

I will probably order the twin chargers on my Model S to future proof myself. A lot of charging stations here in the UK are all the slow kind, but as more and more powerful electric cars come to market I expect to see more powerful charging points.

Objective1 | May 17, 2013

@scoops Ask yourself: "Will I need to charge at home faster than around 50km/hr?" This would only occur if you go on a very long drive, get home, and need to go on another very long drive right away. With a Tesla, usually you won't exhaust your range in a day's normal driving, so recharging over night to top up is no problem. At least that's the experience of many drivers.

The twin chargers will only matter if Tesla doesn't roll out SuperChargers on routes you take (I realize this is unknown.)

How many 50+ amp AC connections do you expect to encounter and need to charge at?

scoops | May 17, 2013

Thanks @objective1. I suppose the idea for the twin chargers is that you don't know how charge points will develop in the future. If more lekky cars come on the road with longer rangers such as the Tesla then I would suspect charge points would be upgraded to provide a faster charge.

You're point about charging at home is spot on. There is free installation here in the UK for a 16A charger, and extra £75 gets you a 30A system. There is also an offer of 75% funding, which is why I might consider the Tesla charger, if Tesla qualify as a government approved installer.

EVTripPlanner | May 17, 2013

I have a spreadsheet and tables at that provide charge rates/times for different circuits.

I'm not sure what charging cable is provided in the UK, but you should only need an outlet installed, not a "charger". Here in the US, I had a NEMA 14-50 outlet installed, which provides 40A (80% of 50A circuit) at 240V. Using real-world charging efficiency and energy/mile, this yields about 24 miles/hour of charge (though 9.6 kW at rated 308 Wh/mi would be over 30 mph at 100% efficiency, when you consider more realistic 345 Wh/mi and 85% charge efficiency, it comes down to 24 mph). You can download the spreadsheet and plug in your assumptions, of course.

hamer | May 17, 2013

Scoops, I may be misunderstanding you, but you may be misunderstanding what you need for your home. I don't know much about the UK, but you don't need a "charger," that is already built into the car. What you need is a receptacle to plug the car into, at the maximum reasonable amperage and voltage you'd need.

Here in the US, a not uncommon circuit is 50 amp 240 volt (what we'd use for an electric range here) which will charge 31 ideal miles in an hour or about 27-28 rated miles in an hour. If you need more than that capacity at home, then you could consider twin chargers.

You don't need a J1772 charger in your home because the charging equipment is in the car. All you need is the electricity for the Tesla cable to plug into, and your local Tesla people should be able to tell you what you need.

jat | May 19, 2013

The bigger problem is you don't know exactly what the charger for the car will look like in the UK. European cars will use the Mennekes connector rather than the Tesla connector in order to accommodate 3-phase charging. You could run the wire, but I wouldn't put any particular EVSE there until those details are decided.

Ampfreak | May 19, 2013

Tesla will deliver a 3-phase charger with the european MS. I haven't found details to this incorporated charger but a red CEE wall socket with 3Phases + Neutral + Earth should be installed by an electrician. With 3 x 16 Amps you get 48 Amps @ 230V = 11040W. This allows you to fully charge your 85KW MS in ~8h over night, which suits most users.

shop | May 19, 2013

I would call Tesla UK and ask them, since no one here even knows what kind of plug/charger the UK version of the Tesla wants/needs.

mallynb | May 19, 2013

Scoops --

Residential power distribution in the UK is 4-wire 3-phase 416 volts line-to-line, 240 volts line-to-neutral. Usually, residences are wired with single phase 240 volts, line-to-neutral. All lighting and appliances operate at this level.

Three phase is rarely a residential wiring practice. In large apartment buildings it may be there. If so, internal wiring is simply distributed among the phases to furnish single phase 240 volts about the building.

The Tesla can be plugged directly into any outlet. No "charging box" is needed.

However, the amount of current available for charging is likely to be limited by house wiring capacity. An electrician can advise you about an upgrade. With the dual charger option, you will need an upgrade that will furnish 80 amps continuously.

Seattle | May 19, 2013

One more point of clarification - some other cars like the leaf do need the "charger box" that you see (they use the j1772). The Tesla's in the US can use these j1772 because there is an adapter, but we don't require the charge box itself, we can just use a regular outlet, which is an advantage over some other cars like the leaf.

Alex K | May 20, 2013

@both | MAY 19, 2013: One more point of clarification - some other cars like the leaf do need the "charger box" that you see (they use the j1772). The Tesla's in the US can use these j1772 because there is an adapter, but we don't require the charge box itself, we can just use a regular outlet, which is an advantage over some other cars like the leaf.

A J1772 EVSE is not a "charger box", it's simply a switch that switches the line voltage onto the cabling after sending a signal out. The Tesla does come with a "box" called a mobile connector that uses an identical signaling protocol to a J1772 EVSE, but it has a Tesla connector and switchable plugs that plug into an outlet. Cars such a Leaf can also use "regular outlets", if the J1772 EVSE is portable and has interchangeable plugs.

jat | May 20, 2013

@AlexK - exactly. The only difference is the LEAF uses J1772 as the EVSE/car connector, while Tesla has a proprietary one. The Tesla Mobile Connector is exactly the same as the portable charger that comes with the LEAF, except the car connector is proprietary compared to J1772, and the Tesla EVSE supports more voltages/plugs, and higher current (which the LEAF EVSE can be upgraded to support as well -- my wife charges her LEAF at 16A@240V from a 14-50 plug at a friend's house).