Charger questions? smart/fast/slow/dumb?

Chester

Well-known Member
Having a quick scout I think Octopus rates for Elec in East should be :-
Unit rate (Peak): 15.96p/ kWh
Unit rate (Off): 5.00p/ kWh
Standing Charge: 25.00p/ day

That's precisely what we're paying, off-peak being 00:30 - 04:30. That's perfect for our little EV, and this time of year at around 4 miles/kWh means ~1.25p/mile. I'll take that! :)
 

noiseboy72

Distinguished Member
If you have fitted an external socket of any type, you do need to consider the earthing arrangements. Most homes have PME earthing - so your neutral coming into the building is also your earth, splitting at the meter. If the neutral fails outside of your home, your car could be at mains potential with respect to the local earth, which particularly on a large capacity supply could be lethal if the car is touched.

You should therefore talk to an electrician about having a suitably size earth rod fitting, and the household earth to that socket removing. Just having an RCD would not protect you from this type of fault without the earth rod being in place.

For my money, I would have a 3 phase 32A supply fitted - cables etc, but just fit a lower rated connector and breaker until the time comes to upgrade. This will then be a simple job, as it will just need the breaker and socket replacing - not the cabling and rest of the infrastructure.
 

arenaman

Moderator
My current supplier is 13.31 p p kwh and 21.4 p per day standing charge

Octopus go is 15.9 p p kwh peak and 5 p for 4 hours off peak with a 25p per day standing charge

Is the 4hrs worth switching for?

@ 10k miles a year I'd need to be putting 27 miles a day charge into it, on my current tariff @ £3 per hundred miles (the app says that's what I'm averaging) that would cost me 81p a day to put those 27 miles charge in and would be 30 pence a day with Octopus

So that's 51 pence a day saving on charging the EV if I switch to Octopus that's IF I only charged at home which I don't, I think at least 50% will be charges at work and whilst shopping etc so say 25 pence a day saving, less than £8 a month but then there's the other 20 hours of the day when it's more expensive than my current tariff and with a higher standing charge.

Spending about £600 a year on leccy (without EV) the Octopus tariff is about 20% higher on peak so that's and extra £120 a year, balance against the savings of £8 a month (£96 a year) then it would actually work out more expensive for me to switch, very rough workings out obviously

I think I've spent half an hour of my life working out that it's not worth switching for me, maybe it was time well spent :laugh:
 

Thatsnotmynaim

Distinguished Member
This is the conclusion I came to when I was on a fixed tariff set 12-24 months ago, however when my fixed tariff ended and I then started to shop around I realised that no one seemed to do any good new tariffs. So if you’re on a good tariff stick with it for as long as you can, but if it ends you may be forced to look around. My electric was ~£170 pm on my old tariff and on all the new ones was going to shoot up to £280 pm. With Octopus although they’re a bit more than my old tariff they are a chunk less than any other new / current tariff out there.. Not sure why tariffs have shot up so much recently, probably use the excuse of the ship stick in a canal with some leccy on it…
 

AMc

Distinguished Member
For my money, I would have a 3 phase 32A supply fitted - cables etc, but just fit a lower rated connector and breaker until the time comes to upgrade. This will then be a simple job, as it will just need the breaker and socket replacing - not the cabling and rest of the infrastructure
It’s a thought, the distance between the consumer unit in the utility and the wall is a couple of metres so there’s not much to replace one way or another.

At the moment I’m erring on the simplest low cost solution until we’ve worked out the drive/porch/outbuilding renovation. Assuming my pal is able to switch an internal socket to an external then I should be covered for now. Then make a proper plan for the longer term.
When the outbuilding is a holiday property having a half decent charger will be a draw.
 

IronGiant

Moderator
My current supplier is 13.31 p p kwh and 21.4 p per day standing charge

Octopus go is 15.9 p p kwh peak and 5 p for 4 hours off peak with a 25p per day standing charge

Is the 4hrs worth switching for?

@ 10k miles a year I'd need to be putting 27 miles a day charge into it, on my current tariff @ £3 per hundred miles (the app says that's what I'm averaging) that would cost me 81p a day to put those 27 miles charge in and would be 30 pence a day with Octopus

So that's 51 pence a day saving on charging the EV if I switch to Octopus that's IF I only charged at home which I don't, I think at least 50% will be charges at work and whilst shopping etc so say 25 pence a day saving, less than £8 a month but then there's the other 20 hours of the day when it's more expensive than my current tariff and with a higher standing charge.

Spending about £600 a year on leccy (without EV) the Octopus tariff is about 20% higher on peak so that's and extra £120 a year, balance against the savings of £8 a month (£96 a year) then it would actually work out more expensive for me to switch, very rough workings out obviously

I think I've spent half an hour of my life working out that it's not worth switching for me, maybe it was time well spent :laugh:
Don't forget that those 4hrs aren't just for EV charging. It might be worth calculating what your baseline consumption is overnight and factoring that in too. Plus you can also run things like tumble driers and washing machines if they have a delayed start facility.
 

arenaman

Moderator
Don't forget that those 4hrs aren't just for EV charging. It might be worth calculating what your baseline consumption is overnight and factoring that in too. Plus you can also run things like tumble driers and washing machines if they have a delayed start facility.

Good point but think there'd be objections to me keeping us all awake with the washer and tumbler droning on through the early hours :laugh:
 

Thatsnotmynaim

Distinguished Member
Ha ha, well that’s the point of the night time tariffs, we used to do washer, dryer and dishwasher overnight when we had E7, dishwasher could sometimes be a bit noisy in the kitchen but washer and dryer were in a utility with door that shut so much quieter.. I think it’s the dryer that sucks the juice, washer was not quite so bad from memory..
 

IronGiant

Moderator
We trickle along at nearly a 1kW with background usage, so the 4hrs counts.
 

Thatsnotmynaim

Distinguished Member
We trickle along at nearly a 1kW with background usage, so the 4hrs counts.
Gosh and I thought I was bad at 600-700W, you Bitcoin mining or live in Blackpool Tower? 🤣
 

IronGiant

Moderator
1627848757900.png
 

IronGiant

Moderator
I have no idea what those nasty little peaks starting rom 22:00 are, unless its the tumble dryer.
 

AMc

Distinguished Member
Spent the weekend helping Nuncats out at the Old Buckenham Airshow.
Demonstrating their significantly more impressive off grid solar charging station for their electric sky jeep - and their lead engineer's all electric motorcycle


When we're all recovered I'll come back to the charger.
In the mean time...

1627990295849.png
 

AMc

Distinguished Member
If you have fitted an external socket of any type, you do need to consider the earthing arrangements. Most homes have PME earthing - so your neutral coming into the building is also your earth, splitting at the meter. If the neutral fails outside of your home, your car could be at mains potential with respect to the local earth, which particularly on a large capacity supply could be lethal if the car is touched.

You should therefore talk to an electrician about having a suitably size earth rod fitting, and the household earth to that socket removing. Just having an RCD would not protect you from this type of fault without the earth rod being in place.

Been looking into this in a bit more detail which has been confusing and disappointing in equal measure!

It appears the guidance is that the socket would need it's own circuit which isn't a problem.

It seems like it will be advisable to have the earth rod for the socket as the house is PME which also means the location of the socket may have to move due to all the services buried in the immediate vicinity.

I'm puzzled as to why my metal outside tap - which is bonded to the earth for the PME supply - isn't considered equally dangerous under the same conditions?
Surely the same fault condition would put that at mains potential through the earth bonding and one touch could be very serious?

EDIT
I'm also puzzled that the "granny charger" doesn't have to protect you from the same fault condition (as it appears some dedicated charge points do) by checking the potential across the supplies and proactively cutting the current.
Perhaps it does, VW are very light on the details of what that box actually does.


So RTFM it looks like this is something my particular charger does do - see the next post
EDIT

I may be swinging back to a proper charge point assuming I can get someone to actually install one!
 
Last edited:

AMc

Distinguished Member
I took another proper look at the VW charger and had a chat with my knowledgeable friend who has also spoken with an electrical engineer he trusts and have learned new things!

I did read the manual for the charger before I first plugged in the car but clearly didn't understand the importance of icon 4.

1628765200573.png


So it looks like the VW granny charger has earth fault detection. That is a major load off my mind given I have been trailing the cable out of the utility room window and could have been putting myself at risk of the PME fault I'd read about. :thumbsup:

1628765385190.png


And also from the car manual talking about charging the high voltage battery.

1628765688475.png


I'm swinging back to the idea of using a conventional 3 pin plug on the outside wall.
I'm considering using one of these which has the added RCBO - it doesn't seem completely necessary but in the future someone might plug something in that wasn't as well protected.


I won't be doing this for a couple of weeks or more so if you spot problems in my logic I'm still very happy to learn more!
 

Thatsnotmynaim

Distinguished Member
Can it be locked, if you feel it needs it, to stop somene knicking your granny charger? Although guess your car end locks it anyway?
 

AMc

Distinguished Member
Can it be locked, if you feel it needs it, to stop somene knicking your granny charger? Although guess your car end locks it anyway?

Although the charger is >£200 from VW I'm reasonably confident it will be OK on my drive. We live in a very low crime area.

The type 2 will lock to the car but someone asked that on the Screwfix page and the answer is no.

The actual cover flap does have a padlock loop, but this is because it comes from the standard Storm weatherproof range, the body of the socket doesn't have a matching loop to secure the lock through so unfortunately it isn't possible to lock it shut.

Even if you could lock the cover, there's not much to stop some idiot lopping it off at the plug. It would ruin the charger but criminals aren't always that clever - I once had a window smashed and the tax disc stolen that was expiring that month.
 

ufo550

Well-known Member
Been looking into this in a bit more detail which has been confusing and disappointing in equal measure!

It appears the guidance is that the socket would need it's own circuit which isn't a problem.

It seems like it will be advisable to have the earth rod for the socket as the house is PME which also means the location of the socket may have to move due to all the services buried in the immediate vicinity.

I'm puzzled as to why my metal outside tap - which is bonded to the earth for the PME supply - isn't considered equally dangerous under the same conditions?
Surely the same fault condition would put that at mains potential through the earth bonding and one touch could be very serious?

I'm also puzzled that the "granny charger" doesn't have to protect you from the same fault condition (as it appears some dedicated charge points do) by checking the potential across the supplies and proactively cutting the current.
Perhaps it does, VW are very light on the details of what that box actually does.

I may be swinging back to a proper charge point assuming I can get someone to actually install one!
If you have a spare half hour, you might want to watch the vids in this thread, before you go putting a standard outdoor socket outside for a car charger.

 

AMc

Distinguished Member
I've been reading up a lot about PME faults and earthing!

There is definitely a potential risk, but having very carefully looked at the information available I'm confident I can plug my particular car's charger into a conventional 3 pin socket and it won't result in live bodywork if the combined neutral and earth conductor fail beyond my property.

From the manual...

1628848503771.png
and

1628848549473.png


I'm taking that as evidence that VW and their electrical engineers have fully understood the potential problems with the Earth fault and that their charger confirms the is a good earth before it energises the connector.

I've attached the complete manual page as the VW online manuals won't link.

Screenshot 2021-08-12 at 11-30-13 Digital Manual Volkswagen.png

Anything else I plug into that socket - strimmer or hedge trimmer is already double insulated.

I can see that if you were to simply wire a 3 pin plug into the outside wall then connect it to something "dumb" with a metal case, directly connected to the house ground without any form of fault detection then you could easily kill yourself. I'm not going to do that!
This strikes me as a serious worry about the PME system with people plugging in hot tubs etc. from who knows where.

So I won't be plugging in some "no name" car charger from eBay etc.

I have consulted with an electrical engineer. He has also checked with a colleague to make sure he wasn't taking any risks, who has also confirmed for this particular situation I'm good.

Anyone else reading this - please do your own research and get your own professional advice before you make any decisions.
 

noiseboy72

Distinguished Member
The risk is pretty minimal in reality, as PME failure is relatively rare, but I would not want to rely upon the cut out in the cable to function correctly and provide full protection for any length of time.

Hot tubs and caravans do pose a risk as do garden rooms, but cars being predominantly metal pose a greater hazard and examples I have seen of cables strung across pavements and trees and then plugged into cars are a serious risk, as the neutral and earth could easily fail in that cable due to cable damage and send the car live.

The only fatal example I remember recently was a young girl from a traveller family who decided to have a wee behind her caravan - which was being powered from a nearby house, and was electrocuted due to contact with the tow bar. Quite a sobering reminder.
 

AMc

Distinguished Member
The risk is pretty minimal in reality, as PME failure is relatively rare, but I would not want to rely upon the cut out in the cable to function correctly and provide full protection for any length of time.

If it's been designed properly then it should fail "off" if it fails at all.
I have confidence in VW engineers to hurtle along at 70mph in their car with fly by wire all over the place.

I'm going to start out with this - partly because it's so low cost and quick to do - the socket will be useful in the future for doing the hedges.

In the future we're renovating an outbuilding as guest accommodation and redesigning the garden and drive. At that point I may put in a full EV charge socket as I can see that being an attractive feature for guests and I won't be worrying about what they might be using for their cars.
I hazard a guess that using a tethered charger over dragging the cabling out of the house each time will also be a motivator - not that I'm lazy :)
 
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ufo550

Well-known Member
I'm puzzled as to why my metal outside tap - which is bonded to the earth for the PME supply - isn't considered equally dangerous under the same conditions?
Surely the same fault condition would put that at mains potential through the earth bonding and one touch could be very serious?

An outside tap is generally not connected to an electrical supply, although it can rise to a dangerous potential in fault conditions; hence why you are not supposed to have an ev charging car in close proximity to bonded or extraneous metal work.
 
Last edited:

ufo550

Well-known Member

ufo550

Well-known Member
I've been reading up a lot about PME faults and earthing!

There is definitely a potential risk, but having very carefully looked at the information available I'm confident I can plug my particular car's charger into a conventional 3 pin socket and it won't result in live bodywork if the combined neutral and earth conductor fail beyond my property.

From the manual...

View attachment 1554747and

View attachment 1554748

I'm taking that as evidence that VW and their electrical engineers have fully understood the potential problems with the Earth fault and that their charger confirms the is a good earth before it energises the connector.

I've attached the complete manual page as the VW online manuals won't link.

View attachment 1554750

Anything else I plug into that socket - strimmer or hedge trimmer is already double insulated.

I can see that if you were to simply wire a 3 pin plug into the outside wall then connect it to something "dumb" with a metal case, directly connected to the house ground without any form of fault detection then you could easily kill yourself. I'm not going to do that!
This strikes me as a serious worry about the PME system with people plugging in hot tubs etc. from who knows where.

So I won't be plugging in some "no name" car charger from eBay etc.

I have consulted with an electrical engineer. He has also checked with a colleague to make sure he wasn't taking any risks, who has also confirmed for this particular situation I'm good.

Anyone else reading this - please do your own research and get your own professional advice before you make any decisions.
This is a copy of Amendment 1 for ev charging; Section 722

I don't read anywhere in the VW manual, that its charger would give protection against a lost pen conductor; it only appears to be monitoring for a open circuit cpc (earth). You should verify with the manufacturer.

Has your electrical engineer referenced BS7671 & Section 722?
 

AMc

Distinguished Member
An outside tap is generally not connected to an electrical supply, although it can rise to a dangerous potential in fault conditions
I can see where the earth is bonded to the incoming mains supply and the copper pipe work a couple of feet to the external metal tap hence my puzzlement.

Regarding The other comments, yes my qualified electrical engineer has explained all the relevant regulations and is comfortable that what I’m planning is not in breach of the regs or dangerous.
 

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