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UMC Mains Extension cable

Been thinking of what sort of extension cable I need to get. Initially it will be to fill the void between getting car and a wall connector, but longer term, its going to be about getting me out of a hold.

Pretty sure that I will be ordering everything from Industrial Extension Leads as they come recommended

But, what type of cable? And how long is the UMC - looks to be 20', 6m? If car is nose in, how much further in front of car would the UMC lead reach?

Its a trade off between length and weight/storage size. And I guess, all cables will be just that bit too short. I haven't paced out home requirements. So 15m/13A, 14m/16A I guess, as its thicker cable at that length/size.

Kit 1 or 2 here seems to cover most bases? 14m 230v 16 amp electrical hook-up heavy duty extension lead - kit 2 would allow me to use 13A lawnmower plugged into a backup 16A commando socket that I intend to fit when I get wall connector fitted.

But not sure of risk of car wanting to charge at 16A if connected to 13A 3 pin plug. It needs to be 'idiot' proof.

Not sure that I want RCD on 13A plug as some IP rated sockets would prevent this?

Suggestions on post card on peoples thoughts on having to hookup at non ideal sites.

Or just keep it simple and go 15m 12A 3 pin 15m single socket heavy duty 13amp (2.5mm cable) extension lead
 
Last edited:

DJP31

Active Member
Aug 30, 2015
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I got my car yesterday and plugged in to an external 3 pin plug using the supplied cable and adapter when I got home.

It obviously knows you are using the 3 pin adapter, and will not let you charge over 10A.

I am absolutely not an expert and other than testing it have never used my UMC in 2.5 years of ownership. However, I think I’ve read here that if using it via a 3 pin plug socket at 10 Amps it is wise to check the plug isn’t heating up. It’s related to these sockets not being designed for that level of draw for extended periods, so turning it down might be advisable.

@arg who be my go to or @WannabeOwner for knowledgable advice on this.
 
I am absolutely not an expert and other than testing it have never used my UMC in 2.5 years of ownership. However, I think I’ve read here that if using it via a 3 pin plug socket at 10 Amps it is wise to check the plug isn’t heating up. It’s related to these sockets not being designed for that level of draw for extended periods, so turning it down might be advisable.

@arg who be my go to or @WannabeOwner for knowledgable advice on this.
Thanks for the feedback, I actually cut it back to 7A overnight for exactly that reason, didn't want to feel the plug as it was sheeting down!
 

WannabeOwner

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Nov 2, 2015
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no heating

I think? that depends what you plug it into, not how well made it is? So can still inadvertently plug into a socket that looks OK but actually the wiring is old, tired, no RCD protection ...

I always check the plug after a while for heat (when staying at Relies etc.)

Begs the question whether it is worth having some additional protection on the extension cable to avoid the situation where Supply is poorly protected.

I've plugged into an external 13 AMP socket at a hotel car park, no idea what it was for, probably a leaf blower in Autumn! and dangled a cable out of the hotel room window with car parked below ... obviously not much ability to know what the Supply side a like.
 
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LukeT

Member
Apr 9, 2019
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UK
I have made my own. I had the option to make it 16A-capable using the UMC to 16A adapter as well but felt it would be too easy then for someone else to draw 16a from a 3 pin socket by using an adapter at the other end, so I didn't. I figured in the long term likely use is almost all at other people's houses, so 3 pin 10a. Still used the thicker cable though, as seems generally recommended.
 
How long is the UMC - I can only see 20’ so 6m. If charging nose in to a socket, how much spare at front?

I’m looking at 16A commando as I intend to install it as a backup. But if the UMC reaches forward of the car enough, then I may not need 16A extension.

My initial requirement is very short term temporary.

Since posting, I had a thought about what if I take car to Europe and need charge from domestic supply. Mainland European sockets never seemed robust even for low level consumption but I am sure I am wrong. But what do people use for hooking up to these?

Don’t want to choose a cable that I may not be able to reutilise in future.

The 16A commando setup looks most flexible except for risk of accidentally drawing > 10A if plugged into 13A supply. Will everything remain as is if there is a power failure whilst charging or will car renegotiate with UMC and change current back to what UMC tells it?

Thinking out loud, maybe safest is long 13A socket and a short 16A commando to 13a/3 pin lead.
 

LukeT

Member
Apr 9, 2019
731
338
UK
My approach was to make up a 3 pin extension which has a letterbox connection at the plug end. So I can easily make up a euro end for it if that situation arises.

Making up a short separate simple 16a to 16a would be so easy and cheap I'd probably have done that separately even just for the short term, but my 16a socket position doesn't need it. I might do it for 32a though, if tesla ever get the adapters back in stock. I've been waiting 6 weeks.
 

WannabeOwner

Well-Known Member
Nov 2, 2015
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Only problem is that it’ll be outdoors. Are these UMC things waterproof/resistant? I.e. can I leave under car?

I've left it "under the car" for a one off, but might be better to get something more robust if it will be every day for a month or so.

A DRiBOX perhaps?

what if I take car to Europe and need charge from domestic supply.

Apart from the flimsy nature of many sockets in EU, and the lack of Earth on some, the French don't care which way round Live/Neutral are connected to the building (not all EVs care either, but Tesla does). So you need the ability to swap Live/Neutral; if you have a self-wired plug that will be easy, if it is moulded then consider an adaptor. Tesla sell Schuko adaptors wired each way round, so a pair them might be prudent.
 

WannabeOwner

Well-Known Member
Nov 2, 2015
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Manual also says don’t use with extension cables

hehehe ... I read that too. Not sure what is different about the extension cable and the wire from 13 AMP socket back to the Grid ... or the, somewhat longer, cable out to the North Sea ...

Greater risk I imagine, but staying with a mate and using their frayed lawn mower cable is one thing, but is an an appropriate extension cable, properly looked after, a risk I wonder?
 
Apart from the flimsy nature of many sockets in EU, and the lack of Earth on some, the French don't care which way round Live/Neutral are connected to the building (not all EVs care either, but Tesla does). So you need the ability to swap Live/Neutral; if you have a self-wired plug that will be easy, if it is moulded then consider an adaptor. Tesla sell Schuko adaptors wired each way round, so a pair them might be prudent.

I believe that Gen 2 UMC as currently shipping no longer cares about reversed live/neutral. 32A Blue Commando Adapter for Tesla Model S/X/3 Gen 2 UMC
 
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hehehe ... I read that too. Not sure what is different about the extension cable and the wire from 13 AMP socket back to the Grid ... or the, somewhat longer, cable out to the North Sea ..

honestly, growing up my dad used to use tin foil to replace burnt fuses. Never had a house fire. I agree it’s irresponsible but I think if you have a good cable you’re safe.

I suspect the difference between an extension cord and above is the protection that’s built in at each step.
 

WannabeOwner

Well-Known Member
Nov 2, 2015
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How does this compare to the cable recommended above?

Your cable is 1.5 diameter. it will have 6M of Tesla cable on the end, so whether 1.5mm is sufficient for the overall length I don't know, but I deliberately bought "one size up" to avoid having an issue with combined length, and also for some extra redundancy / less heat generation.

plug looks rigid, rather than rubberised. Not sure if that matters.

Doesn't look like H07RN-F cable. H07RN-F is very tough, and cold resistant, so less likely to suffer from abuse if trailed along rough tarmac etc.

Cable above is 24.66

Possibly that is a different animal?

This one is 5M and £15.67 if you want 1.5mm or £18.67 if you want 2.5mm. Still isn't £10.99 though ...

5m single socket heavy duty 13amp black extension lead

No allegiance, I got mine from them and am happy with it
 
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