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Discussion Starter · #1 ·
I've been having a think about the general restrictions we all have to suffer associated with slower charging than we would like. My only experience is with a Nissan Leaf, which of course depends entirely upon its battery for power, and for which the fastest possible charging is desirable. I was wondering about what is the fastest feasible available domestic charging.

Many of us 40 amp connections to showers, immersion heaters etc. That, if my understanding is correct provides 9.6kw (240v * 40a). But the Nissan Leaf is restricted to either 3.3kw or 6.6kw charging. Is there any technical or cost reason for Nissan to have gone for these levels? Why not opt for a 10kw charging speed, given that that could take advantage of what is a relatively common available power in the domestic situation?

How easy is it to go for a higher amperage than 40 in the home? Are there reasons associated with local grid restrictions which would prevent this standard being universally supplied?
 

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A UK home typically has a 60 to 100 Amp supply fuse, not that every home in the street can draw that much simultaneously. Even now your installer shouldn't install a 32 Amp charger on a 60 Amp supply if you already have a 40 Amp shower as you'll overload the supply if you run both together. Even a 16 Amp charger with a 40 Amp shower on a 60 Amp supply would be problematic as you can easily overload the supply.

On the continent 3 phase in houses is much more common with a corresponding reduction in the number of Amps per phase and potentially a limit of 16 Amps on a single phase before a large device (like a cooker) needs to be 3 phase.
 

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Discussion Starter · #3 · (Edited)
OK, so there is an upper limit of 40 amps applying to domestic installations.

Would it be technically feasible for Nissan to have fitted their cars with 10kw chargers? Or are 3.3/6.6kw chargers cheaper to produce? Or was it just an arbitrary decision? It just strikes me as reasonable to try to get the fastest possible charge. Supplying a 10 amp charge to a 10kw charger would still charge at 10 amps, but it would have the capacity to charge faster if a higher current was available.

Edited to remove typo.
 

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OK, so there is an upper limit of 40 amps applying to domestic installations.

Would it be technically feasible for Nissan to have fitted their cars with 10kw chargers? Or are 3.3/6.6kw chargers cheaper to produce? Or was it just an arbitrary decision? It just strikes me as reasonable to try to get the fastest possible charge. Supplying a 10 amp charge to a 10kw charger would still charge at 10 amps, but it would have the capacity to charge faster if a higher current was available.

Edited to remove typo.
It would seem reasonable to expect higher power chargers to be larger and more costly.

Many EV onboard chargers are cooled. The presence of waste heat could suggest that efficiency drops as current increases.

Finally for a high power charger to throttle back to a low current would suggest a significant amount of internal switching is taking place. Such switching can give rise to harmonics (mains-bourne interference) which can then influence other electrical devices such as noise on audio, flickering TV picture, flickering lights in the extreme.

Thus a higher power charger will potentially cost more money, use more space in the vehicle, be subject to a dimishing number of places where you could use it, lead to reduced efficiency (and thus higher bills and/or more CO2), and could be more of an issue from an interference perspective.

(And as per my earlier post a higher power single phase charger is not legal in many countries with more widespread use of three phase power, so they'd not see any upside at all)
 

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A lot of the restrictions are based upon the use of 110v. Most EVs are designed for US usage, as were the original standards for charge connectors. Current is doubled with the lower voltage. In addition people always want longer cables, longer cables means higher voltage drop, etc etc. If you have higher power single phase cables they would become rather large and heavy, its all a compromise.
While we have 40+amp supplies to showers and ovens, they are genarally not running at full tilt for 6+ hours. Even this cabling will get hot in the house when drawing 32amps for long periods.
 

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3 phase 16A delivers roughly 11kw, and is perhaps where EVs will end up. With some clever switching and a Type2 socket you could also pull up to 48A from a single phase, so with the right design you get decent domestic and public speeds.
 

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This is a interesting topic. Like the others I suspect it has a lot to do with price vs performance. Remember, the cars that are on the road today were designed many years ago. There was less choice of chargers available then and their prices were way up on those of today. We are looking at EVs today and the chargers and prices available today and thinking why didn't they do this or that. In fact, we should be looking at the chargers and prices available 5-7 years ago if we want to see what options they had during the design phase and so more understand why some of the decisions were made.

I am rather surprised that that Nissan has gone down the route they have with charging though. I suspect they will change over the next few years to have faster chargers and type 2 AC connectors with 3-phase capability rather than the J1772. Maybe not on the Leaf but future models may well be more in line with today's standards.

The issue of faster charging at home though may be a bigger issue. As has been said already, homes in the UK have main fuses of up to 100A. If we are to allow for faster charging at home then this may need to be reviewed. Also, the local supply may well become inadequate and require upgrading if a lot of people in a small area bought EVs and wanted to charge at high rates. The Electric Avenue project is already looking at these kinds of issues.

Ultimately though... do we need faster charging at home? Right now perhaps not as most people charge up overnight and with a 20kWh battery that only requires 16/32A to fully charge overnight for a Nissan Leaf sized BEV. But things are changing fast. It won't be that long before battery capacities will be doubled and then trebled (hopefully) and that will mean that faster home charging may be necessary if we want to fully charge overnight. Already there is the Tesla Model S with 60-85kWh and that can only just be fully charged overnight at 32A. Already we are in the realms of needing faster home charging.

It will be interesting to see how this all pans out.
 

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3 phase 16A delivers roughly 11kw, and is perhaps where EVs will end up.
It already has ended up there in tiny little Netherlands for public charging though, a defacto street charging standard of single posts providing double 11kw output apears to be the norm so they could still increase power to 22kw from some of them if they wanted without any supply issues. Perhaps the reason Telsa Europe HQ is in Amsterdam and not Boris's "EV capital of Europe"?

In mighty blighty, "Leading the Pack" :confused:according to the Transport Minister Baroness (Kramer) in charge of charging, you might find a working double headed post if you are lucky but the chances are it will not be 2 x 7Kw but 1x 7Kw and 1x 3.3Kw.:mad:

Anyone know or like to guess the chances of that being upgradable to even a single 11kw on its existing power supply?

We are still using Victorian sewers in London meanwhile becasue they had something called foresight back then and used it to plan ahead!

Perhaps an insight in to this back slapping government's real intentions for EV uptake?

For domestic charging your 60Amp or 100Amp home fuse, unless already compromised through overheating, will not blow immediately that the current meets the max fuse rating threshold. It will allow temporary overload such as putting the 5th hob ring on to reheat to some degree so the fuse rating number isn't as solid a barrier as it first appears. On a slow blow fuse a temporary overload of even double ampage can be handled for a short time according to WiKi. The cooler it is and better ventilated, the longer it will take to blow.

Not suggesting intentional overload, just explaining the realities of accidental overload.
 

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3 phase 16A delivers roughly 11kw, and is perhaps where EVs will end up.
Mercedes are doing just that but maybe because they are targeting the home market. 3 phase 32A is ~ 22kW which Zoe and optionally the Model S can charge from.

The problem is not many homes in the UK have 3 phase service. Upgrades to 3-ϕ are expensive or impossible.


3-ϕ destination charging may be the future if pack size grows. But should it be free? 30kWh of power per customer is starting to be real money.
 

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I had a 70A (~16kW) Tesla Charging Station that worked fine on our 100A supply. I removed it while some work was undertaken in the garage and never reinstalled it because in reality 32A (7kW) meets my needs at home with a ~55kWh battery (I usually charge at 7A-30A during the day on Solar).

At our new location we will have plenty 3 phase power and will use that for offering high power AC and DC to guests (only time I can think that I'd need more than 7kW at home).

The biggest issue with higher power (11-22kW) incar chargers is heat not cost. Heat can be useful however for preheating the car in northern climates like ours... both the CODA and AZD vehicles used waste heat from the charger and motor/inverter for cabin heating.

One interesting development is low cost CHAdeMO which might allow that interface to become a de facto standard for power levels above 3kW :rolleyes:
 

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We have 100A supply and asked Western Power if we could upgrade and they could only offer us another separate 100A supply. Try charging 6 Leafs with 100A it's a nightmare.
 

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We have 100A supply and asked Western Power if we could upgrade and they could only offer us another separate 100A supply. Try charging 6 Leafs with 100A it's a nightmare.
Can your roof(s) help a little bit with solar in sunny Cornwall? If so PM me and I will help advise on the best ways it can be done:).
 

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In mighty blighty, "Leading the Pack" :confused:according to the Transport Minister Baroness (Kramer) in charge of charging, you might find a working double headed post if you are lucky but the chances are it will not be 2 x 7Kw but 1x 7Kw and 1x 3.3Kw.:mad:

Anyone know or like to guess the chances of that being upgradable to even a single 11kw on its existing power supply?
As armoured cable is not the expensive part of an installation and no more than £5 per metre for 16mm 4 core cable which would easily support two 22kw 3 phase AC charge points, it would seem sensible that all new public charge points have this size of cable supplying them to future proof the site.

Brusa have had a 22kw charger for a couple of years now which will allow a 60A DC charge rate on 3 phase and defaults to single phase for slower overnight charging.

These charge points would be far cheaper to spread around rather than the rapid chargers for car parks etc. where a car can be parked for a few hours.
 

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We have 100A supply and asked Western Power if we could upgrade and they could only offer us another separate 100A supply. Try charging 6 Leafs with 100A it's a nightmare.
Your supplier should be able to offer you a 3 phase supply from the road which would be capable of supporting six Leafs (Leaves?) charging. :)
 

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We have 100A supply and asked Western Power if we could upgrade and they could only offer us another separate 100A supply. Try charging 6 Leafs with 100A it's a nightmare.
Perhaps battery storage will be the answer in a few years time. A constant 100A single phase supply with enough battery storage could let you do 24 complete Leaf charges in a 24 hour period (assuming you didn't use any power for anything else!)
 

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Perhaps battery storage will be the answer in a few years time. A constant 100A single phase supply with enough battery storage could let you do 24 complete Leaf charges in a 24 hour period (assuming you didn't use any power for anything else!)
Or how about a more intelligent charger that can monitor other load in the home (or maybe just instrument key circuits like cooker/shower) and adjust it's output accordingly.... in real time
 

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It won't be too many years before the area substation will monitor load and send a request either wirelessly or via the supply wiring to devices such as EV's, fridges, freezers etc to reduce load at peak periods.
It is peak load for short periods that requires extra mostly unused capacity in the system and our transmission system will be far more efficient if loaded closer to its nominal capacity rather than with peaks and troughs.

EV's and other intermittent loads can be set to only switch on when capacity is available if allowed by the user.
I forsee it being a bit like intelligent Economy 7 with similar charges.
 

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It won't be too many years before the area substation will monitor load and send a request either wirelessly or via the supply wiring to devices such as EV's, fridges, freezers etc to reduce load at peak periods.
It is peak load for short periods that requires extra mostly unused capacity in the system and our transmission system will be far more efficient if loaded closer to its nominal capacity rather than with peaks and troughs.

EV's and other intermittent loads can be set to only switch on when capacity is available if allowed by the user.
I forsee it being a bit like intelligent Economy 7 with similar charging.
I have visions of an Orwellian future where I am in a queue waiting for my kettle to boil, dreaming of the days I could freely make a cup of tea whenever I wanted....!
 
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