Hi,
I am however confused about the second charger option, the Tesla rep suggested it had minimal value, however I have read a couple of posts here on the forums suggesting it might even be of value at home, is anyone able to provide any advice?
It's a real head-scratcher whether to get the dual chargers; the cost of getting it upgraded later is huge (at least if UK pricing tracks the US), and whether or not you will actually get any benefit out of it depends on factors that it's almost impossible to know - how you will use the car (will your driving patterns remain the same for the whole time you have the car? I don't think mine will...), and what the installed base of public charging stations looks like in the particular places you happen to want to visit.
I eventually decided to go with the dual chargers, though there's a strong argument for just taking the single charger and using the cash to buy the CHAdeMO adapter instead, when it eventually appears.
To actually take advantage of dual chargers, you need both an EVSE (charge point) that can supply more current than the single-charger car can consume, and a driving pattern where the faster charge actually makes a difference to what you can do. If the EVSE can't supply the power, then the dual charger car will charge at exactly the same speed as the single charger car; and if for example you are planning to leave at 7AM, it doesn't really help that the car is ready to go at 3AM rather than 6:30.
For most people, the dual chargers is much more about charging on trips than charging at home. Few UK homes have more than 100A single phase coming in from the street, so will struggle to provide even the 43A that is the max a single charger Model S can consume - and you probably don't need it anyhow. With 32A charging (7.3kW), it takes less than 12 hours to charge from absolute dead empty to absolute full range charge, so the car can probably fully charge overnight anyhow. With a less common EVSE configuration you could push the single-charger car to 11kW and so charge in under 8 hours. However, the need can arise depending on your lifestyle - I have been analysing my (ICE) driving over the past year or so to see how it would work out driving the Tesla, and I have had exactly one occasion where the ability to use dual chargers at home would have been important: I had a day when I was leaving on a family holiday to Devon in the afternoon, and I suddenly had a business meeting in Northampton in the morning; after that 100-mile round trip in the morning I would have needed to refill 30kWh to get back to the range charge needed for the trip to Devon - 4 hours on a 32A EVSE, 3 hours at single-charger max, or 1.5hours at dual charger max. On that actual day, I had about 2 hours available...
More plausible for using dual chargers might be charging at work - most commercial/industrial premises have 3-phase supply, and finding a spare 32A of 3-phase capacity at an office/industrial site is much more likely than finding 96A of single-phase at home. And the scenario of coming in from somewhere, spending a couple of hours in the office and then heading out somewhere else seems more likely than similar timing at home.
Out on the road it's a different matter. Single charger means a maximum of 30 miles range added in an hour of charging; dual charger can get up to 60 miles of range per hour of charging (assuming 300Wh/mile). If you are in a service area sitting waiting for the charge needed to get to your destination, that would be a huge difference. And there do seem to be a moderate number of public charge points where 22kW is available (and unlike the USA, it's not just the Teslas that want high current AC - Renault are favouring even higher current AC). On the other hand, many of the existing high-current public charge locations in the UK also have CHAdeMO at the same location - twice as fast again, so the CHAdeMO adatper makes much more sense if you believe this pattern of deployments is going to continue in the future. But then again, these sites often have only one CHAdeMO; what if the CHAdeMO is out-of-order or already in use? Having the dual charger means the backup option only takes twice as long, rather than 4 times.
So in summary, the dual chargers make sense if any of:
- You have a charging location at home/work with more than 10kW of spare power available and have a driving pattern where you often drive more than 200 miles in a day
- You believe there are likely to be public charging locations in places you will want to travel to (maybe abroad?) that have high current AC but not CHAdeMO and you actually make trips where you drive more than 200 miles in a day.
- You believe the Tesla CHAdeMO adapter could be a long time coming and/or you don't trust the reliability of publc CHAdeMO locations.
I have Chargemaster fitting a Type 2 32A charger at my house in the next week or so, will single vs dual chargers make a difference at home on a 240V, 32A Type 2 charger?
It shouldn't do: 230V@32A = 7.36kW, so within the rating of the single charger.
However, I have seen a rumour (on one of the threads on here about charging in Norway) that implies the single charger car, though capable of 10kW, can't take more than 3.7kW through a conventionally-wired type-2 single phase connector. I have no idea if this rumour is true (see below), but if it were true the dual charger car would be better off when connected this way. However, a different configuration of the EVSE would solve the problem even if this is true.
Not exactly related, but for the electrically curious my wife has a BMW i3 on order as well, the house feed is 100A, and we are having 2 x Type 2 chargers fitted at home, I believe Chargemaster's plan is to install a small sub board off the main feed into the house and run a cable/cables to the two chargers from the sub board.
Sounds reasonable. But with two 32A chargers and only 100A into the house you are pushing things already and certainly don't have the capacity to go up to 62A or 96A for the Model S (that you'd need to take full advantage of the dual chargers). What's really needed for this (likely extremely common) situation is an intelligent EVSE that can offer more power to one car when other loads in the house/2nd car are not on, and reduce it when demand goes up. I'm sorely tempted to build my own, not having seen such a piece of kit available commercially yet.
Technical info
The exact spec of the UK/Europe cars doesn't seem to be entirely clear. The best I have been able to understand from reading here and Tesla's announcements etc. is:
- The single-charger car has a maximum total rating of 11kW, dual charger at 22kW.
- The input to the car is configured for three-phase, but with effectively 3 separate chargers, one for each phase, drawing between phase and neutral. There are reports that the car won't charge in the absence of a neutral connection (even though the load should be balanced and so no current flowing in the neutral). So it has 3 inputs at 16A (single charger) or 32A (dual) each.
- The car can therefore straightforwardly charge from 16A single phase (32A dual charger) without anything special happening - this is just the 3-phase setup where two phases happen to be switched off.
- The car is specified to be able charge from more than 16A single-phase (40A single/80A dual according to the Tesla website). To do this requires that the chargers are connected in parallel - ie. 2 or more of the onboard chargers are connected to the same phase. What is not clear is the mechanism(s) available for this reconfiguration.
- The UMC (supplied with the car) is internally a 3-phase device, but has an adaptor for 32A single phase (blue 'commando' socket), and this works with single charger cars. I believe, but don't know for certain, that the blue adaptor parallels this input to all three of the phase inputs to the UMC and so to the car.
- It is less clear what happens you are using a standard IEC62196-2 EVSE. Normal wiring of single phase to a type2 socket just uses the L1 pin (and the standard sockets can be rated for up to 64A per phase, though common cables are up to 32A only). If the car does nothing special, it would be limited to 16A (single), 32A (dual). For a 32A standard EVSE to be useful, the car would have a set of contactors to disconnect the charger normally connected to the L2 pin and connect it in parallel on the L1 pin instead. Ideally, the car would also allow the L3 charger to connect to the L1 pin in the same way, for up to 96A input in the dual charger case.
- The reports from Norway suggest that the car certainly doesn't have the full switching capability that it would ideally have. Possibly it has the limited switching capability for single charger cars to draw 32A from a single phase input. Possibly it has no switching capability at all - in which case single charger cars would be limited to 16A single phase from a standard single-phase EVSE.
- If the car is indeed limited in this way, all is not lost: when wanting to install an EVSE with a high current single phase supply available, you can simply buy a 3-phase EVSE and wire the one phase that you have to all three phase inputs (and set the current rating to 1/3 of the actual supply accordingly, so if you have 32A single-phase available, you would configure the EVSE for 10A three-phase. This is what people in Norway have reputedly been doing.
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