Granny home charging instead of Type 2?

[Fogey]

It seems that a lot of the problem with 13A-plug charging is the safety issue associated with loss of protective earth. Does anyone make an appropriate stand-alone circuit isolator which detects loss of earth? (Preferably using an earth monitor probe input.)

 

[Geoffers]

It seems that a lot of the problem with 13A-plug charging is the safety issue associated with loss of protective earth

Is 'the safety issue' detailed somewhere? Not something I'm aware of. Anyone know of a report from the HSE or other official body.

 

[Jto]

That’s the thing. I’m not currently on an off peak tariff. Although it is something I am thinking of switching to.

Another question then, I have a 16A (I think) commando socket in my garage specifically for a fancy high powered pressure washer I used to have. Could this be utilised with an Ohme commando cable and would it be better than a granny charger?

Hi
would just like to add you could do a fast charge at a station when your car gets low then do a granny charge from 80% to 100% on the granny charger at home and this will balance the battery. You probably only need to do this once aweek on the miles you do. Cost of fast charge will depend on which charger you use but will be a lot less then petrol you would use for the same journey.
Also which MG4 are you thinking of getting the short rage has a battery that likes been charged to full regularly but the long rage only charge to 80% and only charge to 100% when going on a long journey or balance the battery once a month.

 

[tsedge]

Is 'the safety issue' detailed somewhere? Not something I'm aware of. Anyone know of a report from the HSE or other official body.

I don't know of one, but the general issue is:

• 13A sockets and wiring charging a car for many hours will get hot.
• Heat can cause fatigue in the connections.
• Fatigue in the connections will typically increase resistance, therefore generating more heat.
• The cycle can end with a serious fault, such as an earth-neutral short which could potentially make the car live to the touch and result in electrocution.

Modern chargers include special detection circuity to avoid this: they can detect such faults (and others) and immediately disconnect the car, isolating it so that it is safe to touch.

Found some explanation here (for a specific charger, but applies generally):

BG SyncEV - Earth Rod explanation

syncev.co.uk

 

[tsedge]

It seems that a lot of the problem with 13A-plug charging is the safety issue associated with loss of protective earth. Does anyone make an appropriate stand-alone circuit isolator which detects loss of earth? (Preferably using an earth monitor probe input.)

This would be useful and would potentially render a similar level of safety without paying for a dedicated charger.

 

[Jto]

Could you explain this in a bit more detail please as I have seen it mentioned before but do not understand it?

What makes plugging in the car different to say a washing machine into the same socket?

Hi
A washing machine is used for a short time on a ring main, I had power from my fuse board out to the garden and to my shed which I used a cable that could take 32amp and had a 20amp breaker at the fuse board so nothing else will be used on that line and used good heavy duty products rated to 32amps and did check from time to time that they are running cool.
A ring main has other appliances that can be used which will increase the load on the wiring and breaker so if you had you car on charging on the ring main and then used other appliances at he same time you could over load the ring main. I hope this
explains why you see reports of problems.

 

[tsedge]

Seems like the main danger is people behaving like idiots:

"The charity surveyed 1,500 electric vehicle owners, including both all electric and hybrids, revealing a shocking 74% believe that a lack of public charging points near their home has led them to use domestic multi-socket extension leads, not suitable for outdoor use, to charge from the mains in their home.[2] This is despite almost 9 out of 10 respondents admitting they’re aware these should not be used outside.[3] Over half of EV users who charge with the aid of an extension lead, meanwhile, have left cables running to their vehicle when it’s been raining.[4]

The worrying research also found responses from those surveyed show that 75% of those who charge using a domestic extension lead even admit to ‘daisy-chaining’ extension leads to reach their vehicle; a method whereby multiple extension leads are plugged into one another to cover a longer distance.[5] Daisy-chaining is advised against in all circumstances due to the heightened risk of electric shock and even fire that it brings about."

Source:

Charging Your Car From A Mains Could Cause Electric Shock | PetrolPrices

Results of a survey show that a lack of charging points is forcing drivers of EVs to put themselves at risk by charging their cars using extension leads.

www.petrolprices.com

 

[Fogey]

This would be useful and would potentially render a similar level of safety without paying for a dedicated charger.

Exactly!

The problem is actually to do with the way we provide domestic earthing in the UK - which is via the Neutral line. If the Neutral connection gets broken (outside of the user's premises), then earthed appliances float up to line voltage. Which isn't too great a problem, as everything and anyone within the premises follows suit.

But an EV sitting in the driveway is surrounded by true earth, so anyone touching it will "see" Line voltage plus battery voltage - and this could easily prove fatal.

Luckily, such faults are very rare - but nevertheless, if and when they do happen, having an EV plugged in is by far the most problematic situation.

As I see it, most domestic charging stations protect against this by monitoring Line-to-Neutral voltage, and immediately isolate the vehicle the moment this goes out of spec. But a better method is to monitor true external earth via a probe, and compare this against domestic earth.

Speaking personally, when I get my first EV (the MG4 on order), I'm quite happy to charge at 6A, so use of a 13A socket would be quite good enough - if it weren't for the - remote - possibility of the above fault occurring.

 

[tsedge]

As I see it, most domestic charging stations protect against this by monitoring Line-to-Neutral voltage, and immediately isolate the vehicle the moment this goes out of spec. But a better method is to monitor true external earth via a probe, and compare this against domestic earth.

Speaking personally, when I get my first EV (the MG4 on order), I'm quite happy to charge at 6A, so use of a 13A socket would be quite good enough - if it weren't for the - remote - possibility of the above fault occurring.

6A would be a safe level for long term charging. Of course, most people won't know, won't care and won't set this.

Are you saying that the older requirements to have an earthing rod as part of the charger installation would be a better solution and the current policy (in-charger detection) is potentially less safe?

 

[Fogey]

6A would be a safe level for long term charging. Of course, most people won't know, won't care and won't set this.

Are you saying that the older requirements to have an earthing rod as part of the charger installation would be a better solution and the current policy (in-charger detection) is potentially less safe?

Probably slightly less safe, and more prone to false triggers than monitoring and comparing true earth via a probe against mains earth.

 

[Shengis]

Seems like the main danger is people behaving like idiots:

"The charity surveyed 1,500 electric vehicle owners, including both all electric and hybrids, revealing a shocking 74% believe that a lack of public charging points near their home has led them to use domestic multi-socket extension leads, not suitable for outdoor use, to charge from the mains in their home.[2] This is despite almost 9 out of 10 respondents admitting they’re aware these should not be used outside.[3] Over half of EV users who charge with the aid of an extension lead, meanwhile, have left cables running to their vehicle when it’s been raining.[4]

The worrying research also found responses from those surveyed show that 75% of those who charge using a domestic extension lead even admit to ‘daisy-chaining’ extension leads to reach their vehicle; a method whereby multiple extension leads are plugged into one another to cover a longer distance.[5] Daisy-chaining is advised against in all circumstances due to the heightened risk of electric shock and even fire that it brings about."

Source:

Charging Your Car From A Mains Could Cause Electric Shock | PetrolPrices

Results of a survey show that a lack of charging points is forcing drivers of EVs to put themselves at risk by charging their cars using extension leads.

www.petrolprices.com

This is wild! The stupidity, nae ignorance, of people never ceases to amaze!

Anyway, further to my initial query on this thread, I’m going with a proper home charger being installed by a proper installer. No messing about.

 

[BugEyed]

Are you saying that the older requirements to have an earthing rod as part of the charger installation would be a better solution and the current policy (in-charger detection) is potentially less safe?

There are arguments for and against both methods used by level 3 charge points, but the key is that they are both orders of magnitude safer than level 2 charge points.

I’m going with a proper home charger being installed by a proper installer. No messing about.

A wise move.

 

[Lovemyev]

There are arguments for and against both methods used by level 3 charge points, but the key is that they are both orders of magnitude safer than level 2 charge points.



A wise move.

I retied my Granny charger after using for short time, after getting a wall box installed back in 2015.
One advantage of having both a wall box and a Granny unit, is that you have a back up plan !.
Ever since having the wall box installed, our Granny unit has been hanging on the wall of our garage.
Only getting used when we travel to area's where we know / expect the public charging services to be poor.
It's a back up plan IF we have any issues with our wall box.
Always have a back up plan when it comes to EV's !.

 

[Redoralive]

I used the granny charger for the first few days as the car arrived before the charger was installed.

I do 300 miles a week just commuting so my usage is a bit higher.

If You're sensible it should be fine to use, but a home charger is worth the extra money. With ICE being phased out, the charger will become standard on houses and with greater demand they will be more expensive to install. Plus I've noticed a lot more competition at the public charge points.

 

[Lovemyev]

Another thing to think about, when considering buy a wall box over a Granny lead is this.
Are you on a cheaper overnight tariff ?.
If you are a high usage case, then you are unlikely to reach a full SOC, from a low SOC and therefore maximise that cheaper tariff, when charging from the much slower Granny lead.

 

[pete3112]

There is an in-between option that is much cheaper. A granny charger is just 10amp. You can install a 16 amp socket either off an underused ring main or a 2.5mm circuit from the consumer unit. Easy and cheap to do. You can pick up a 16amp inline charger from Amazon for under £150. Make sure you get one with a 16amp plug as a square pin 13amp can only sustain 10amps.

What rate would a 16 amp charger charge the car at from a 16 amp socket please?

 

[charlie bravo]

Thanks for that. I am really struggling to get my head round this kWh thing.

You’re saying the charge is 2.2 kWh so 10 hours would be 22 kWh of charge. So surely the amount of time it takes does matter then, no? And if not, how do I know how much that will cost in electricity?

As already said in 4hours on go but get 38 miles witch work for me

 

[wiz043]

I am starting to get put off in buying an MG4 or any other EV now due to all the charging hassles regarding a granny charger.
I only cover around 150km (94 miles) average weekly and was just going to charge the MG Long Range in my garage with a standard 240 volt 10 amp power source which we have here in Australia.
It would probably only need charging around 40% (24kw) once weekly but would probably need 10 hours or so which is not advised here on this forum.
I suppose the other option is to charge it for 5 hours twice weekly or after each small trip for a couple of hours or so. Perhaps this would put less stress on the home electrical system of which I obviously know nothing about?
Due to my low mileage I did not think it was worthwhile spending big bucks on a wall charger or whatever.

 

[Geoffers]

But an EV sitting in the driveway is surrounded by true earth, so anyone touching it will "see" Line voltage plus battery voltage - and this could easily prove fatal.

I realise line voltage is bad enough (240V AC) but surely the in-car charger has built in protection to prevent DC battery voltage becoming live through the lead?

I have a granny charger which can supply 6, 8,10 or 13A. 6A is perfect for me as the car is on the drive much of the time during the day and I can absorb my generated solar surplus.

 

[tsedge]

What rate would a 16 amp charger charge the car at from a 16 amp socket please?

16A will give you something like 3.5kW. 32A home chargers can do 7kW. This is without factoring in losses, which will slightly reduce the rates.