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Discussion Starter #1
I want to make up an extension lead so that I can use the granny charger at my mothers house. I want to try and match the cable thickness of the granny charger, which looks to be around 10mm? I don't have any verniers at the moment, so can't be 100% certain? Can anyone confirm this?

The only cable I can find in the shop, of similar thickness to the granny charger appears to be armoured cable, which is very ridged and not pliable. I want some thick flex cable, exactly the same as on the granny charger. Any idea where I could buy some from?
 

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2020 BMW i3S 120Ah BEV
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This Electrical Cable Size Calculator – Melissa Electricals says 1.5mm^2 for 25m of cable. This is probably overkill for cable that's not hidden inside walls .. You can probably get away with 1.25mm^2 cables if you're just talking about an extension cable.

Or you could just buy one of these..

 

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Discussion Starter #3
Do you think this will be okay then:

I definitely want to buy just the cable rather than a made up extension lead, as it gives me more flexibility, and I may even end up taking it through walls. But I definitely want the flexible stuff and not ridged armour cable.
 

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Does your Granny cable have a temperature sensor in the 13A plug?

If so your new cable will need a couple of extra cores to service that if your are grafting on an extra length not just using it as a socketed extension.
 

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Discussion Starter #5
Does your Granny cable have a temperature sensor in the 13A plug?

If so your new cable will need a couple of extra cores to service that.
Well if the cable is thick enough it won't heat up and cause that issue. That's why I wanted to try and match the original thickness of the cable.
 

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Just wondering, would your mother's granny by your great granny?

You know it is the quality and thickness of the core rather that the overall cable thickness that matters right? @mrdr_ev gives good advice - if the extension is of sufficient quality the granny will likely be first point of failure, get hot and cut out before any issues with the extension.

I may even end up taking it through walls
:unsure:. If you want a temporary fix get a good quality extension. If you want something more permanent or robust get an electrician to fit a dedicated socket (or commando, or charge point), but get advice from a professional rather than a randomer like me on the interweb.
 

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i would go with mrdr_ev suggestion extension already made up with IP54 rating for outdoor use
The component parts individually probably cost more
 

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I definitely want to buy just the cable rather than a made up extension lead, as it gives me more flexibility, and I may even end up taking it through walls. But I definitely want the flexible stuff and not ridged armour cable.
The masterplug part I quoted comes with a removable plug and removable waterproof socket if you wish to pass it through walls/etc. The waterproof socket in particular is very useful.

Yes some generic three-core 1.5mm^2 cable would be fine too, but then you need a plug and socket!

tommydog1 said:


Well if the cable is thick enough it won't heat up and cause that issue. That's why I wanted to try and match the original thickness of the cable.
As stated above the thickness of the cable casing is not important, it's the thickness of the conductors inside the cable that matters. That said, any old extension lead is fine as long as it can carry the current without overheating.
 

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1) you cannot just cut the plug off and extend or replace the cable frequently.

2) use Toughleads

Job done.
 

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Discussion Starter #11
you cannot just cut the plug off
Seems you can!
 

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Discussion Starter #12
As stated above the thickness of the cable casing is not important, it's the thickness of the conductors inside the cable that matters.
I understand that, but unless it's an armoured sheath, the cable thickness is normally a good indication of thickness of the conductor. A thicker conductor will normally come in a thicker cable (not talking about flat cable).
 

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I made extension lead using 10mtr 2.5mm. Plus heavy duty 13amp plus Waterproof Outdoor 13A Storm Switched Single Socket IP66 Outside Use 5055875521957 | eBay

Bit more than you need, but better than less. Cable coils nicely.
 

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Discussion Starter #14
I made extension lead using 10mtr 2.5mm. Plus heavy duty 13amp plus Waterproof Outdoor 13A Storm Switched Single Socket IP66 Outside Use 5055875521957 | eBay

Bit more than you need, but better than less. Cable coils nicely.
Thanks for that recommendation. Did you terminate with a 3 pin plug, or did you wire directly to the consumer unit? I was thinking with a 2.5mm cable, a normal 3 pin plug would be a real squeeze in terms of room and providing effective stain relief.

After looking all day, I decided to go for some 2.5mm cable. It's overkill, but gives a good margin, as I read of people using thinner extensions and the charger turning off due to overheating.
 

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I already had a good 3 pin plug, it is basically a standard but allowed a thicker cable entry. Was a cosy fit, not too tight. Soldered the ends.
Also made one using 4mm cable, that is really overkill, just wasted money on it, as far to heavy and wouldn't fit under the cover in the boot, and was really a squeeze to get the three pin plug on that.
Hope that helps.
 
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