Is there a maximum length extension cable for use with the Tesla granny charger? I’m taking a trip to France later this year and one charging option at my destination is to run a cable from the apartment to the car and use Tesla’s granny charger to top up the battery overnight. I’m not quite sure how long an extension cable I’d need, so wondering if there is a recommended maximum length I need to consider. If I go for this option I’d get the cable from a retailer who offers good quality EV cables.
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Maximum length extension cable for use with granny charger?
- Thread starter rob@rar
- Start date
I've done exactly that using a 15m cable coupled to the granny charger. The cable was from Tough Leads, great build quality and the one I opted for had a built-in trip. No issues. I usually check the socket 15 minutes in and then again periodically to see nothing getting too hot. I've got through 2 week holidays in France without using public charging doing this - but don't tell Vrbo
MrBadger
Badger out
I use a 25m 2.5mm cable when I stay in a remote farmhouse in Snowdonia. Works perfectly and It doesn’t even get warm.
I also have a 25 meter extension that I made up with 2.5mm cores. Never a problem. It actually has commando connections but with 13amp 3pin plug and socket adapters that can be added to the ends… so in use it’s probably nearer 30 meters when used in 13amp mode.
I ordered a tough leads cable this evening to extend my granny charger.
They go up to 25m. I ordered the 10m.
toughleads.co.uk
They go up to 25m. I ordered the 10m.
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.
If the cable is thick enough, the limit is what you can carry in practice.
Thinner cables have a higher resistance and therefore a higher voltage drop across them.
As long as the voltage drop doesn’t take the UMC below it’s minimum accepted voltage, you can go as far as you want really. Obviously joining multiple leads together creates obvious points of resistance and failure and is obviously a bad idea.
25m is a looong lead already.
Thinner cables have a higher resistance and therefore a higher voltage drop across them.
As long as the voltage drop doesn’t take the UMC below it’s minimum accepted voltage, you can go as far as you want really. Obviously joining multiple leads together creates obvious points of resistance and failure and is obviously a bad idea.
25m is a looong lead already.
M1tch
2021 M3P with EAP
I’ve got a 10m builders waterproof extention. (I think it was from B&Q - bright yellow thing) Single male plug to single enclosed female plug and been using it for 2.5 years to trickle charge at work. Not had any issues with it getting warm or any issues in some terrible downpours it’s been in.
I don’t advise copying this, but I do have a colleague who uses a 25m reel / drum type cable thing. Wraps it in a Tesco carrier bag if it’s going to rain and doesn’t unravel the whole thing either. Somehow nobody has died and he’s not tripped the power to the building/car yet!
It’s people like that that give us a bad name….
I don’t advise copying this, but I do have a colleague who uses a 25m reel / drum type cable thing. Wraps it in a Tesco carrier bag if it’s going to rain and doesn’t unravel the whole thing either. Somehow nobody has died and he’s not tripped the power to the building/car yet!
It’s people like that that give us a bad name….
Maximum cable lengths
The 13A extension leads provided on the website are a maximum length of 25m (15m for hot tub leads). This is not an arbitrary length, but one set with due consideration to cable resistance and voltage drop. Cable Length Imagine watering your garden with a 20m hose pipe. The hose pipe exerts...
The numbers are generous enough to allow for the ~6m 4mm2 of the UMC
As others have said, the official length is 0m. One other consideration is you mentioned this option for France. How are you planning to adapt the UK extension lead to Schuko? You can't just use a standard plug adaptor as they are usually limited to 7A and occasionally 10A. I have made up a short Schuko to 13A waterproof UK socket, using 2.5mm core flex. This also allows you to swap over Live & Neutral if you need to, as French wiring can be a bit random as to which pin has been wired as Live & Neutral, especially in rural settings.. You can also limit the UMC to charge at 10A to be sure, especially if you're using an extension cable, even if its fully unwound.
FWIW I use the Schuko adaptor for the UMC when charging at our place in France and it allows 13A charging from our external socket - Schuko sockets being rated at 16A. Its a useful option to have when travelling in France, as is the Octopus Electroverse card as it works with a decent number of the various public charging networks in France.
FWIW I use the Schuko adaptor for the UMC when charging at our place in France and it allows 13A charging from our external socket - Schuko sockets being rated at 16A. Its a useful option to have when travelling in France, as is the Octopus Electroverse card as it works with a decent number of the various public charging networks in France.
I have the commando tails so bought this 16A 2 Pin Style Schuko Plug To Industrial Socket Adaptor - Socket Converter | eBay
I've since also bought the Schuko tail for UMC. Seems always out of stock on the UK website so I got a colleague in France to order one.
I've since also bought the Schuko tail for UMC. Seems always out of stock on the UK website so I got a colleague in France to order one.
Thanks, if I go ahead with the plan I'd get a cable made with a heavy duty Schuko plug at one end and a waterproof UK 13A socket at the other, as the cable would stay in France so no need to convert a UK plug with an adapter. If I do use an extension cable it would be during cold winter temperatures, hopefully reducing the possibility of overheating.
Before I commit to getting an extension cable I'll need to find out what the local destination charging facilities are like as the nearest Supercharger is 48km and more than 1500m in altitude difference. I'm also have to measure the length of the cable run I'd need from the apartment to the nearest point I can park my car to work out whether this is a viable plan, but it's been very helpful to get everyone's comments on the possibility.
My experience is that public charging in France is way ahead of the UK. Most small towns and even some villages have chargers. Sometimes just 22kW AC points, but they still work and are perfect for destination charging. Chargemap probably is the best resource for French chargers. There's a great new(ish) network called IECharge, (iecharge.io) which are putting rapids in off the main highways. Minimum install of two units, each capable of charging two cars at a time, one 320kW unit, one 160kW, all at 0.30€ per kWh using tap to pay. Worth keeping an eye on, they have 500 sites identified for install next year and over 1,000 for 2025.
Have a good trip
Depends on the location, my experience of public destination charging is
1) Gets busy at the weekend
2) Will get ICED if there if it saves a 10 meter walk
But definitely a wider array of destination chargers than the UK in general
Drew57
Active ember
I have a 10m Masterplug heavy duty lead to use with the UMC (reported as 6m). For any/all extension cables it is recommended to fully uncoil & as a result I've never noticed any warmth whenever charging at 10a.
I’ll be heading to a French ski resort, Les Arcs. There are 4 Shell Recharge 22kW chargers near my apartment, but they seem continually occupied either by EVs or ICEd whenever I’ve taken a look during the ski season. I’d like to have a fallback position just in case it’s impossible to get on to those 22kW chargers when I need to. Currently there’s not much in the way of high speed charging infrastructure in that part of the Alps. Nearest high speed is a 150kW Tesla Supercharger, but that’s nearly 50km away and I’d like to use that when I’m passing rather than making a specific journey just to charge up.
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