Granny charger

[Basicbob]

Hi I’ve been using a granny charger for over a year and it works for me.

However before on the app it use to charge between 2kw and 3 kw.

I noticed it would flicker between 2kw and 3kw. I’m pretty use it use it charge faster over night.

Now it’s always at 2kw. Nothing has changed any ideas how I can squeeze a little bit more out of it?

Does it matter if the granny cable is rolled up?

 

[MrMoonUK]

You shouldn’t be using this as a long term charging solution, it’s called an occasional charger for a reason. You’ve been lucky your sockets haven’t melted

 

[MrBadger]

Its voltage dependent which might explain the fluctuations (W=IV etc and rounding). Car normally shows the mains voltage with AC charging. For single phase, 10A max at 230v nominal is 2300W, but you won't get exactly 230v - allowed range is 230v -6%/+10% so quite a variance allowed and is perfectly normal.

But as always with long cables, always use fully unwound. And check for overheating.

 

[MrT3]

Your cable needs to be unwound to avoid unnecessary heat.

The charging speed change may be related to your mains voltage, maybe it isn’t as high as before - maybe you have resistance in your socket/extension lead…..

 

[Basicbob]

Why can’t granny chargers be used long term?

My house has complete new re-wiring with a new modem fuse box.

When I charge it over a long period eg 10 hours the plug socket isn’t even warm.

Should I stop?

 

[bhanorthy]

Granny charger is perfectly acceptable as long as you have good modern wiring. Been using for over 2 years with no issue albeit without any extension cable.

If you do need an extension use a heavy duty one rated for continuous 10amp draw.

Living in a rental property where I’m already paying the landlords mortgage I’m not paying for them to have a 7KW charger. 3 pin is sufficient.

 

[Adopado]

Why can’t granny chargers be used long term?

My house has complete new re-wiring with a new modem fuse box.

When I charge it over a long period eg 10 hours the plug socket isn’t even warm.

Should I stop?

If it’s not getting unduly warm you’ll be fine. A full charge point install gives you some additional safety protection but we’ve not read of anyone having a problem as a result of using the UMC aside from overheating that results from old sockets/wiring.

[From time to time I do some Google searching to find out if anyone in the world has ever been electrocuted as a result of their faulty charging equipment … none so far. There are about 7 million EVs. So, yes there’s a risk but it’s a small one. ]

 

[Jason71]

You shouldn’t be using this as a long term charging solution, it’s called an occasional charger for a reason. You’ve been lucky your sockets haven’t melted

Who calls it an occasional charger? I have never heard it called that?

 

[Tony Hoyle]

No device would be allowed to be sold if it could melt your sockets. They actually have a thermal cutout to prevent this even in the case of poor wiring. Problems with granny chargers tend to be things like using them on coiled extensions or using them in the wet without proper cover.

 

[GlynG]

Comments regarding melting sockets and the charger is not designed for anything more than occasional use actually tell you more about the authors ignorance and perhaps the need to create anxiety in others - its complete bull.

UK sockets are rated at 14 amps, ohm's law states - watts equals amps multiplied by the volts, so 14 times 230 = 3220watts (3.2Kws) In the UK we always worked on our supply being 240 volts, its fairly recent that 230 volts are banded about but using the lower figure it confirms our sockets are designed to provide at least 3.2Kws within specification, of course as sockets age and wear and tear it is possible the connectors inside are not making the same degree of contact as when they were new - a good clue of this would be the socket and plug getting very warm, however - if you have any concerns just swap out the socket you will use to charge the car from - a new double socket will cost you under £15 and about 10 minutes to swap - and for an electrician about 2 minutes.

The socket has no idea a car charger is plugged in and to be honest its the same draw as a fan heater / convector heater / Toaster, and less than a Kettle / iron.

The granny charger itself - its designed to charge the car, indeed you can swap the plug end and connect it to a much greater amperage cable - so internally the unit is thermally safe and running well below its optimum when a three pin plug is used, longevity? - like anything else - no one knows how long they will last but on average it will still be working fine in 10 years time.

I, like you, only use the granny charger at home - I have no need for a dedicated charger, so carry on as you are. My charger has always drawn just over 2Kws from day one - never seen any other charging rate from it.

 

[MrMoonUK]

There have been plenty of incidents of occasional chargers melting sockets , just go on other forums. Tesla themselves even say it’s an occasional charger when using the 3 pin adapter. If you want a cheap option get a commando! Any electrician will tell you to not use a 3 pin for hours on end at max

 

[scdoubleu]

One thing to consider is the state of the ring-final circuit connected to the back of the wall socket. The granny charger socket may be in good health, with firm connections to the wiring, but don't discount the possibility of a loose connection elsewhere in the property on the same ring-final.

In normal use this is unlikely to pose a risk. However, drawing 2.5 kW for hours at a time will exacerbate any extant wiring problems.

 

[MrBadger]

In normal use this is unlikely to pose a risk. However, drawing 2.5 kW for hours at a time will exacerbate any extant wiring problems.

What, you mean like this Father in law turned all the heat on at the same time and obviously a lose connection in the filter for the supply tails... Well they do say to get your electrics inspected every 10 years. It had been working fine for best part of 20 years until now...

Thankfully we smelt something wrong and isolated the property. But not until the filter in the supply ended up looking like this.

And before anyone suggested something got overloaded, its a 100A filter in an 80A fused supply, with 32A of heaters on potentially full blast, and may be 16A immersion. So well within spec. But continuous high loads do pose an additional risk.

 

[Jason71]

Tesla themselves even say it’s an occasional charger when using the 3 pin adapter.

Where do they say that?
I have actually read the manual for the car and the one for the UMC and I cannot see anything in there about only using it occasionally.
If what you say is correct would it not qualify as important need to know info that should be in there?

 

[GlynG]

You can never say never but every single electrical joint and connection in a property has the potential to become a problem and I accept the higher the loading the higher the potential - but we are talking "potential" and not probability - unless the wiring or ring main is very old - especially the old rubber insulated Red/Black wiring of many moons ago - However, short of having a rewire even a full inspection has the potential to not identify any issues as cables are buried within the walls. However, people don't give a second thought to plugging domestic appliances in that also have a high current draw and hence I did say an indication there may be a connection issue at a plug and socket was excessive heat build up - and therefore provides a clue something probably needs some attention.

My point was that its irresponsible to advise that a car charger is likely to cause a socket meltdown as if its normal or should be expected.

The supply tails comment - Isn't that something the energy suppliers tell us are checked when they send their unqualified meter readers out as justification for their daily charges and the right of access they have? I have never seen them do anything more than read the meter though they say its also a safety check included.

 

[Pants]

Tesla themselves even say it’s an occasional charger when using the 3 pin adapter. If you want a cheap option get a commando! Any electrician will tell you to not use a 3 pin for hours on end at max

Can you point to where Tesla say this? I can’t find any reference anywhere, and I have never heard of the 3 pin UMC being called an “occasional” charger. I’ve been using the UMC perfectly successfully since I bought my M3P last September. Can’t see the point of spending £hundreds on a 7kw charge point when I don’t need one.

I have converted a 200 year old outhouse in the garden into an office and it’s heated by a 3kw heater plugged into a normal socket. That draws 50% more current than the UMC. After being on for several hours the plug and socket get a little warm but never hot.

 

[RetiredSideman]

Granny charger is perfectly acceptable as long as you have good modern wiring. Been using for over 2 years with no issue albeit without any extension cable.

If you do need an extension use a heavy duty one rated for continuous 10amp draw.

Living in a rental property where I’m already paying the landlords mortgage I’m not paying for them to have a 7KW charger. 3 pin is sufficient.

Do you also pay the bills aswell? Was there a noticeable increase when you bought a tesla and started charging?

I’m also renting till summer in a place with bills included and wanna know if I can suggest paying the extra energy costs if it’s going to increase it by quite abit.

 

[Adopado]

Do you also pay the bills aswell? Was there a noticeable increase when you bought a tesla and started charging?

I’m also renting till summer in a place with bills included and wanna know if I can suggest paying the extra energy costs if it’s going to increase it by quite abit.

The car (in the app) can keep track of how many kWh have been used. If there’s an issue you can use that information to estimate extra costs. People on a special cheap rate EV tariff and doing low mileage are obviously going to have a far smaller impact on their bill. You will be charging at the same rate as for the rest of your consumption so the increase could be considerable.

 

[JonB]

What, you mean like this Father in law turned all the heat on at the same time and obviously a lose connection in the filter for the supply tails... Well they do say to get your electrics inspected every 10 years. It had been working fine for best part of 20 years until now...

View attachment 780189

Thankfully we smelt something wrong and isolated the property. But not until the filter in the supply ended up looking like this.

And before anyone suggested something got overloaded, its a 100A filter in an 80A fused supply, with 32A of heaters on potentially full blast, and may be 16A immersion. So well within spec. But continuous high loads do pose an additional risk.

View attachment 780190

Looking at your first picture it appears the filter unit was connected then shoved inside another box with the tails wrapped round it. That is asking for trouble, surely? It's not going to be able to dissipate much heat like that and I am surprised you didn't have issues sooner. I'd find another electrician if I were you...

Anyway, back on topic - I'm using my granny charger with a 32A commando socket without problems [edited to add: "so far"]. It's on an armoured cable connected direct to the fuse box though, so no ring main involved. I do reduce the charge rate if I'm only topping off, but it's had no issue charging at the full 32A. I had a quote for a Zappi install (a grand) but as we are now about to sell the house I feel I can get by with the granny for a few months. And of course I extracted as much information from the electrician as I could (including maximum load for the incoming supply vs. tytpical load for the house; that is, the available headroom fo the charger).

 

[WannabeOwner]

I'm using my granny charger with a 32A commando socket

I have a commando alongside my wall-charger, as a backup (and the occasional EV that arrives here that has the wrong sort of socket !! for my wall charger)

But wiggling the granny cable in and out seems to put a fair bit of force on the plastic. I'm not sure I'd want to do that often ... my Commando socket wasn't ultra-cheap, but maybe there are more robust ones if planning to frequently remove the cable (in order to have it with you, Natch!)