Charging from a granny lead, dangers?🔥🤔

[richlove]

My current charging solution is to use work chargers, as it's not possible to install one at the apartment (apparently). I'm fully remote, so just pop in to top the car up a few mornings per week, with occasional rapid charge top-ups.

I'm fairly keen to get an extension lead to use the granny charger, running the extension out of the window down to the car park. This wouldn't be every night, more when I need to top-up before a long journey and haven't been able to get in to work. In order to achieve this, I'm considering the following items:

However, on to the point of the post: I've read various horror / scare stories, mostly around fire risk, regarding charging from a granny lead for long period (overnight), though not sure how much credence to give them. Surely, if there was a real, significant danger, not so many people would be using granny leads to charge at all? Is anybody here able to offer a reasonably balanced view of using a granny lead (perhaps with extension) overnight and if there are any real safety concerns?

Read that it may be sensible to use a socket tester and RCD. Just feeling a bit unsure about going ahead with this solution.

 

[IanMK]

Don't use a 13A extension lead. If you must, limit the charging current to 6A in the car and uncoil the lead fully.

 

[Jomarkh]

Sounds like a plan B.
If you can get most of the charging done at work then do the final top up using the granny EVSE.
Just monitor the heat being generated at the various plug and sockets.
What is the state of the wall socket you are going to use?

 

[tsedge]

Limit the charge rate to 6A and fully uncoil as people have said.

If at all possible plug into a dedicated socket with its own circuit breaker at the main fuse board.

The fires have tended to be caused by dodgy house wiring triggered by connections degrading through repeated load cycles, increasing resistance over time and ultimately leading to failure/fire.

Try to get the cleanest electrical path with fewest connections and have a sparky check over your wiring.

 

[IanMK]

Although shutting the stable door after the horse has bolted in regards to using a granny charger, it's probably a good idea while you have a sparky in fitting a wall charger that they test the integrity of the house wiring for you,
Just in case there is an issue with old wiring, best to use a socket on a ring main and not a spur.

 

[richlove]

Cheers, much appreciated. The apartment is a few hundred years old and think the wiring may not be fantastic, so seems it's worth getting it checked over.

 

[richlove]

Don't use a 13A extension lead. If you must, limit the charging current to 6A in the car and uncoil the lead fully.

This lead (from the original post) seems to be widely recommended on various forums, though it's 13A. Are you suggesting it may not be safe or fit for purpose?

EV granny charger 13A weatherproof extension lead

High quality 13A weatherproof outdoor waterproof extension leads heavy duty 1.5mm H07RN-F rubber cable. RCD option. IP66. Designed specifically to overcome the issue created by chunkier plugs on electric vehicles (EVs). 2m, 5m, 10m, 15m, 20m and 25m lengths.

toughleads.co.uk

 

[Guru]

Always a good idea to have the wiring checked and whilst the sparky is there ask him to fit a new socket where you intend to plug in. As someone else said most issues are caused by older corroded sockets creating high resistance and therefor heat. If you're using an extension lead then you loose the heat protection built into the plug that most granny chargers have hence really important to make sure the socket is in good condition and obviously never use a coiled extension.

Whilst granny chargers can present a small risk it's been blown out of all proportion and the number of incidents are tiny compared to the number of people regularly using them. We only granny charged for the first 5000 miles with zero issues however I did put a brand new socket on.

 

[Yorkshire Hillbilly]

I use one of these from my garage:

*Amazon B09K5JFWQT
it's fully uncoiled, only just reaches. The garage is also a separate building and has its own consumer unit. And I've limited the car to 6A

I stuck one of these on the garage end to automatically switch it on / off through Home Assistant

*Amazon B08LZWBTR6
It's actually quite genius... It turns off when I leave the house but, only if it's not drawing any power. And it turns on when I get home then waits for me to open the back door before checking for power draw and turns it off again if there isn't any.

 

[Themist0]

I use one of these from my garage:
View attachment 16913
*Amazon B09K5JFWQT
it's fully uncoiled, only just reaches. The garage is also a separate building and has its own consumer unit. And I've limited the car to 6A

I stuck one of these on the garage end to automatically switch it on / off through Home Assistant
View attachment 16915
*Amazon B08LZWBTR6
It's actually quite genius... It turns off when I leave the house but, only if it's not drawing any power. And it turns on when I get home then waits for me to open the back door before checking for power draw and turns it off again if there isn't any.

Out of interest, I have loads of Kasa plugs, how do you control them when you leave the house… is it linked to your connection to wifi somehow?

 

[Diggsy]

Fairly certain that’s something you can do in conjunction with IFTTT (If This Then That)

 

[Yorkshire Hillbilly]

Out of interest, I have loads of Kasa plugs, how do you control them when you leave the house… is it linked to your connection to wifi somehow?

I use Home Assistant but, I think you could also use Amazon Alexa, Google Nest or Apply HomePod. You'll need something to tell Alexa you're not home but, Nest and HomePod link to your phone and can detect when you leave or enter a place.

 

[Cocijo]

My current charging solution is to use work chargers, as it's not possible to install one at the apartment (apparently). I'm fully remote, so just pop in to top the car up a few mornings per week, with occasional rapid charge top-ups.

I'm fairly keen to get an extension lead to use the granny charger, running the extension out of the window down to the car park. This wouldn't be every night, more when I need to top-up before a long journey and haven't been able to get in to work. In order to achieve this, I'm considering the following items:

View attachment 16902

However, on to the point of the post: I've read various horror / scare stories, mostly around fire risk, regarding charging from a granny lead for long period (overnight), though not sure how much credence to give them. Surely, if there was a real, significant danger, not so many people would be using granny leads to charge at all? Is anybody here able to offer a reasonably balanced view of using a granny lead (perhaps with extension) overnight and if there are any real safety concerns?

Read that it may be sensible to use a socket tester and RCD. Just feeling a bit unsure about going ahead with this solution.

Fairly certain that’s something you can do in conjunction with IFTTT (If This Then That)

I don’t use this particular Application but I use IFTTT a lot on other stuff. I guess your configuration will use geofencing - tracking where you are using your phone and applying the rules accordingly.

 

[IanMK]

Are you suggesting it may not be safe or fit for purpose?

Personally, I've always used 4 amps per square mm as a rule of thumb. This lead is described as1.5 square mm.

 

[Rolfe]

I just got my car and I'm currently at the stage of seeing whether I can get by with the granny charger (supplemented by the occasional use of the public charge point 400 yards from my house) or whether I'll shell out for a home charging point.

Hearing a lot of alarmist talk about these chargers, but I'm not seeing anything to worry about from my point of view. My socket is in my garage and is a metal box, not the sort of thing you get in the actual house, and I'm lucky enough not to need an extension cord. The car has been charging for an hour or so and I went out to feel the plug and socket. Both absolutely stone cold.

I think Guru is right. The things are safe if you have good wiring and buy kit that is specifically advertised as being able to do this job. If you're running it from a plastic socket in a house that hasn't been rewired for many years, and using any old extension lead that happens to be handy, maybe that's not so safe. But if your socket is good and any extension is rated for the job, I don't see why you would need to worry.

My house is only about 27 years old and the electrical sockets installed in the garage by the builders seem well able to cope with charging a car.

 

[tsedge]

I just got my car and I'm currently at the stage of seeing whether I can get by with the granny charger (supplemented by the occasional use of the public charge point 400 yards from my house) or whether I'll shell out for a home charging point.

Hearing a lot of alarmist talk about these chargers, but I'm not seeing anything to worry about from my point of view. My socket is in my garage and is a metal box, not the sort of thing you get in the actual house, and I'm lucky enough not to need an extension cord. The car has been charging for an hour or so and I went out to feel the plug and socket. Both absolutely stone cold.

I think Guru is right. The things are safe if you have good wiring and buy kit that is specifically advertised as being able to do this job. If you're running it from a plastic socket in a house that hasn't been rewired for many years, and using any old extension lead that happens to be handy, maybe that's not so safe. But if your socket is good and any extension is rated for the job, I don't see why you would need to worry.

My house is only about 27 years old and the electrical sockets installed in the garage by the builders seem well able to cope with charging a car.

Good to hear you have a good setup.

Just to explain a bit more, it is repeated cycles that can create a fatigue failure in the electric circuits. People sometimes don't realise that is possible but the thermal cycling can damage poor connections which as they worsen increase resistance in the circuit thus generating more heat and more thermal damage. This can spiral and cause a failure/fire.

The danger isn't "does it work the first few times", it is "will it fail the n-hundredth time"?

Granted with good modern electrics the risk is low - although granny chargers don't include some fault protections that 7kW chargers do - but a lot of people don't think about it and don't check.

 

[tsedge]

People typically seem to behave badly:

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

 

[Guru]

People typically seem to behave badly:

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

I'm calling bullsh*t on that! 74% of EV drivers charge using an extension and granny charger? I know quite a few EV drivers now and not a single one charges using the granny let alone with an extension lead.

 

[Rolfe]

If we leave the safety issue for now, is there any other reason apart from speed for not using the granny charger?

 

[siteguru]

Efficiency. The slower the source charge speed, the lower the overall efficiency. So the same amount of kWh into the car needs more kWh from the source, so costs more. Example:

50kWh into the car
At 80% efficiency (typical for a granny) that is 60kWh from the source, so 60 * 34p = £20.40
At 90% efficiency (typical for a 7kW wall box) that is 55kWh from the source, so 55 * 34p = £18.70