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Discussion Starter #1
I recently tried to charge our new-to-us 65-plate R240 Zoe via a genuine Renault granny lead I bought off eBay. With the second-hand but otherwise unused granny lead plugged into a 13A socket in the garage the car gave the 'Battery Charging Impossible' message and refused to charge.

I see from the forums that the Zoe is sensitive to earth resistance, and I know that the wiring in our house is at least 20 years old if not 40. The garage socket is also a very long way from where the supply comes into the house, and the cabling to get there includes: 100A fuse, meter, RCD, old-school fire-proof conduit, main consumer unit, ring main cable, twin+earth, old-school fuse box, SWA, the garage CU with RCD, and finally more T+E to the socket. As a result I rather suspect our old wiring is the issue rather than the 2nd-hand granny lead (though I will try and check this by plugging in somewhere else when I can).

We don't really need a full 7kW socket install at home (free 22kW charging at Uni nearby), but it would be useful if we could at least charge the car using the granny lead from time to time.

Without shelling out for a massive house re-wire, I am considering whether to just ram an earth spike into a patch of open soil beside the garage and wire this to the garage consumer unit. Would this solve my issue? Would it additionally improve the house wiring at all? Or is there a good reason why I shouldn't do this?

Looking forward to hearing what forum experts think...
 

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It's much cheaper to get a 7kW charger installed than re-wire your house!

Also, granny cables aren't designed for regular use.

And never depend on public charging!
 

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Have you tried charging your car using your granny lead at another location? It's probably worth giving it a go to confirm the lead isn't faulty.
 

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I'm not a qualified electrician, so the following is just my initial reaction.

I'd get an electrician to measure the impedances in the cabling. That way you at least know what you are starting from.

Given that the existing cabling is old and with numerous connections, it's probably a bad idea to run 10A over it continually. There's a difference between running a kettle for 4 minutes and charging an EV for 10 hours. Improving the earth won't get over this.

Most of the cost of a new connection will be installing new cable, so you might as well future proof the installation and put in cable capable of carrying more than 13A. But it sounds as though your issue is getting from the house to the garage - I assume that is were the SWA is. Is it simply buried, or are you lucky enough for it to be in a conduit? It would be nice to pull through new cable.

If you can't, how old is the SWA and what diameter conductor? If it is adequate, can you make new connections to it at each end?

You need to take professional advice with regard to earthing, including assessing the earthing arrangements for the property. The Zoe looks at the impedance between neutral and earth. Improving the local earth may not solve the problem. It just might be the impedance in the neutral if there are poor connections in the chain.
 

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Presumably the car charges fine on a public charger, you mention 22kW at Uni????

So the car is good.


Fault could be with the "new" granny lead. Ask a friend if you can plug your granny lead and your car into their socket. If it works, you are left with a problem in your house/ garage wiring.

Based on your suggestions so far, probably best to get a competent person to investigate, i.e an electrician. You will get all kinds of well meaning but misleading ideas on this forum, ignore them and get the electrician to systematically test and investigate.

Note, chances are you just have one of two faulty joints that just need remaking.
 

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Discussion Starter #6
And never depend on public charging!
Actually they now have sixteen fast-charge bays at the nearest University site to us. We're fortunate its the primary conference and accommodation campus and so reflects EV demand from the wider community rather than just what students and staff can afford to drive! After that there's a bunch of two-bays and 4-bays dotted around at other buildings and campuses so there're always other options. We're lucky the Scottish government is pushing EVs. We still haven't needed to pay for a charge since we got the car.
 

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Discussion Starter #7
Have you tried charging your car using your granny lead at another location? It's probably worth giving it a go to confirm the lead isn't faulty.
Not yet. Only a few of our pals have driveways so we have to work out who we can ask for a borrow!
 

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I'm not a qualified electrician, so the following is just my initial reaction.

I'd get an electrician to measure the impedances in the cabling. That way you at least know what you are starting from.

Given that the existing cabling is old and with numerous connections, it's probably a bad idea to run 10A over it continually. There's a difference between running a kettle for 4 minutes and charging an EV for 10 hours. Improving the earth won't get over this.

Most of the cost of a new connection will be installing new cable, so you might as well future proof the installation and put in cable capable of carrying more than 13A. But it sounds as though your issue is getting from the house to the garage - I assume that is were the SWA is. Is it simply buried, or are you lucky enough for it to be in a conduit? It would be nice to pull through new cable.

If you can't, how old is the SWA and what diameter conductor? If it is adequate, can you make new connections to it at each end?

You need to take professional advice with regard to earthing, including assessing the earthing arrangements for the property. The Zoe looks at the impedance between neutral and earth. Improving the local earth may not solve the problem. It just might be the impedance in the neutral if there are poor connections in the chain.
I've already turned the power off and checked and tightened all the cable connections for the sockets I could get to.
I think you're right though - getting a spark in to measure and test the circuits is probably the next step. I'd been considering about this anyway because I'm thinking we should upgrade to a split board CU, and still need to add a solar inverter into the mix. Since we'll be pushing and pulling different currents at different times for different purposes than the system was originally configured for it'd be nice to know that everything we can bring up to better spec is there or thereabouts just for our own peace of mind.
 

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Actually they now have sixteen fast-charge bays at the nearest University site to us.
Ohh, Scotland! Always depend on public charging ;)
 

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old-school fuse box
Are you planning to sell your house in next few years? If you are, you might as well spend the money to upgrade your electrics sooner rather than later. These days buyers (and especially surveyors) are quick to spot old electrics and will knock the cost off their offer price.

With cost and size of RCBOs coming down I recommend using all those as far more flexible and future proof. Just had spark do it at our house using Hager and at a rental property using a cheaper brand (forgotten name).
 
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