EV Chargepoint - Wiring Options

[JohnW2]

For the instructions to state "Minimum conductor cross section area 6 mm2, or higher depending on installation specifics and local regulations" is not exactly correct - "Minimum conductor cross section area 4 mm2, or higher depending on installation specifics and local regulations" would be.

That is clearly correct in terms of the requirements of BS7671 in terms of current-carrying capacity.

However, stillp has indicated that functionality of some of these chargers can be impaired by the impedance of the feed. If that's the case (ridiculous thought that may be), it might be appropriate for the manufacturer to specify a minimum CSA of 6mm² (albeit a bit silly without any mention of length!) in order to make it more likely that the charger will work satisfactorily - even if 4mm² would often be adequate in terms of CCC.

Kind Regards, John

 

[EFLImpudence]

Therefore it will need working out so there is no point stating 6mm² minimum.

The instructions state it works >210V and less than 12% Volt drop and as you, yourself have often stated, there isn't much difference between volt-drop and low supply voltage.

 

[stillp]

I hope your memory is unreliable - they aren't allowed to make a charger which fails above 245V.

Quite.

 

[stillp]

there isn't much difference between volt-drop and low supply voltage

There is - low supply voltage is more or less constant, volt drop will depend on the instantaneous value of the current drawn, which as I stated earlier can upset some designs of charger. At least it used to a few years ago.

 

[JohnW2]

Therefore it will need working out so there is no point stating 6mm² minimum.

As I have agreed, if impedance is the issue, it's silly to talk about a minimum CSA without also talking about length. Indeed, if impedance is all that crucial, they should presumably talk in terms of the L-N loop impedance (all the way back to substation.

The instructions state it works >210V and less than 12% Volt drop and as you, yourself have often stated, there isn't much difference between volt-drop and low supply voltage.

Indeed I have, but stillp has suggested that we may be dealing with a fairly unusual situation here, in which it is not so much the general 'supply voltage' (as seen by charger, including any VDs) that matters but, rather, the transient VDs due to "spikes of charger demand" travelling through the impedance of the supply cable. We do not usually have to take such 'transient VDs' into account.

Kind Regards, John

 

[motorbiking]

If you are thinking of a Tesla Model 3 (I am), then I guess you are referring to installing a standard 32A industrial socket?

TESLA specify 6mm² in their guidance note and and the regs require an interlocked socket cf. 722.55.201.1 (ii) or (iii)

note also earthing requirements for PME installations referenced in a previous reply.

https://www.tesla.com/sites/default...nstall_guide_industrial_socket_blue_DEC16.pdf

Have you placed your reserve? I'm keen on the Model 3 too, but I think its more likely that I'll go Model S as the 3 wont actually have cleared the backlog in the next 12-18 months. There are a couple of things that are putting me off though: warranty, parts availability and what happens once that £20-30k battery stops working. I'd kind of like my 70 grand car to have more than an 8 year life.

Tesla aren't going to up their game until somebody else produces something remotely competitive and frankly there is nothing on the market.

 

[davelx]

Have you placed your reserve? I'm keen on the Model 3 too, but I think its more likely that I'll go Model S as the 3 wont actually have cleared the backlog in the next 12-18 months. There are a couple of things that are putting me off though: warranty, parts availability and what happens once that £20-30k battery stops working. I'd kind of like my 70 grand car to have more than an 8 year life.

Tesla aren't going to up their game until somebody else produces something remotely competitive and frankly there is nothing on the market.

I'm biding my time to see what other manufacturers do. My Ampera is still going perfectly so I'm happy to wait.

I've driven the model S and a friend of mine has one, but I don't do enough mileage to spend that sort of money.

 

[ban-all-sheds]

I'd kind of like my 70 grand car to have more than an 8 year life.

Then if you buy one take care of the battery - the warranty does not cover replacement if you damage it through neglect/misuse.

Or buy a £70K petrol engined car - that sort of money could get you a very tasty nearly new car with massively more than 8 years life ahead of it.

 

[flameport]

and what happens once that £20-30k battery stops working.

You pay £30k for a new one.
Or more likely, just buy a whole new car.

Electric cars are very expensive, and there is no getting away from that.
There will be no used / second hand market in them either.

 

[motorbiking]

As I understand it, there are ways to claim the tax and NI off the car, so for me its effectively a 50% discount.

 

[winston1]

You pay £30k for a new one.
Or more likely, just buy a whole new car.

Electric cars are very expensive, and there is no getting away from that.
There will be no used / second hand market in them either.

The batteries are often leased for £xx per month. So no sudden costs fora new one.

 

[winston1]

As I understand it, there are ways to claim the tax and NI off the car, so for me its effectively a 50% discount.

Tell us more.

 

[motorbiking]

https://www.tesla.com/en_GB/support/incentives

 

[ChewChew]

Wow lots of posts some of which have developed a life of their own.... I'll address the ones I have comment for and then get back on to the original request.

Some EV chargers are very sensitive to voltage drop, so don't scrimp on the size of cable - I'd suggest 6mm².

Thats a good point, but its the charger built into the car that is sensitive to a volt drop. I think this is a safety feature - the on board charger attempts to pull as much current as advertised by the chargepoint, but if it detects a voltage drop outside a certain tolerance it will reduce the current draw to prevent overheating of the chargepoint/cabling/etc...

If you are thinking of a Tesla Model 3 (I am), then I guess you are referring to installing a standard 32A industrial socket?

TESLA specify 6mm² in their guidance note and and the regs require an interlocked socket cf. 722.55.201.1 (ii) or (iii)

note also earthing requirements for PME installations referenced in a previous reply.

https://www.tesla.com/sites/default...nstall_guide_industrial_socket_blue_DEC16.pdf

Yep its a model 3. I've placed a refundable deposit about month after the reveal event, but RHD UK versions will not be released until summer 2018. I guess this will give me time to see how well they are received and perform before I commit to an order.

 

[ChewChew]

From the following replies it seems that option 1 is popular - stick with light and mains socket as spurs off the house and run a separate cable for the chargepoint.

4mm radial off a 32a MCB in your CU

more knowledgeable posters may have better ideas

Some EV chargers are very sensitive to voltage drop, so don't scrimp on the size of cable - I'd suggest 6mm².

So, would option 2 be unworkable? I still like the idea of a CU in the garage so I can have more lights and power. If this combined with the chargepoint this is too much to pull down one cable, I could run two cables - one for the CU and the other for the chargepoint? Would it be ok to run these cables next to each other? Any suggestions for diameter?

Has the cable to go outside?

If so, use SWA.

The difference in price and OD is minimal, so I would go for 10milli.

No, the run will internal to the house and into the attached garage.