Granny charger vs 7kw
Discussion
Sorry if this has been covered hundreds of times already, but, do I really need a 7kw charger?
Got an EV arriving in the next few weeks, with current usage it'll cover 7k/yr, say 10 miles Mon-Fri, with the rest at the weekend. If I drop onto an EV tariff (I assume I can even with a granny charger), then I can set the car to charge during the off peak hours and add at least 13kw within the 6hr window.
The car will have a useable battery of 62kw, and I've pessimistically estimated the efficiency to be 3m/kw. In order to maintain a decent available range at all times I've estimated I'd need to charge the car overnight once a week on a 7kw, and once every 2 days on a 3pin.
Now, my installation isn't straight forward, so I've estimated £500 for a 7kw charger, and £500 labour, whereas getting an external 3pin fitted would be around £100.
So, for 7k/yr would you bother paying £900+ for a 7kw, or just stick with the 3pin?
Got an EV arriving in the next few weeks, with current usage it'll cover 7k/yr, say 10 miles Mon-Fri, with the rest at the weekend. If I drop onto an EV tariff (I assume I can even with a granny charger), then I can set the car to charge during the off peak hours and add at least 13kw within the 6hr window.
The car will have a useable battery of 62kw, and I've pessimistically estimated the efficiency to be 3m/kw. In order to maintain a decent available range at all times I've estimated I'd need to charge the car overnight once a week on a 7kw, and once every 2 days on a 3pin.
Now, my installation isn't straight forward, so I've estimated £500 for a 7kw charger, and £500 labour, whereas getting an external 3pin fitted would be around £100.
So, for 7k/yr would you bother paying £900+ for a 7kw, or just stick with the 3pin?
also on the 3 pin life. as long as you keep on top of it and know ahead of time when you are going on longer trips etc its managable. Also on IOG and been fine. a bit annoying if they go ahead with the 6 hour limit at least in its iteration where its 6hr total wether its 6hr total smart charging vs 6hrs max outside the overnight window. but should still manage
the only problem really is if you have longer trips back to back. in which case may have to bite the bullet and public fast charge for those occasions.
the only problem really is if you have longer trips back to back. in which case may have to bite the bullet and public fast charge for those occasions.
I spent the first 12 months / 8k miles using granny charger only (i think I used a public charger 3 times, and one of those was to see how they work). No issues at all.
I only had a 7kw installed when my wife also got an EV a few weeks ago because she does 20k a year, otherwise I'd never have been able to justify the cost.
I only had a 7kw installed when my wife also got an EV a few weeks ago because she does 20k a year, otherwise I'd never have been able to justify the cost.
OldGermanHeaps said:
Seen a few granny chargers melt sockets
Can you give more details. My limited experience is with a Ring charger for my old Leaf. It’s the charger that normally cuts out as it’s v.sensitive, especially if I choose 13amps over 10 or 6.
Shirley a charger fault you’ve come across?
It’s certainly true that granny charging is best via a good quality 32amp cable rather than some 30 yr old legacy spur.
OldGermanHeaps said:
Seen a few granny chargers melt sockets
There are plenty available where you can limit the charge rate which massively reduces the heat generated and likelihood of this happening.Based on the OP''s requirements he could run at 6 or 8 amps (1.4 or 1.9kW) and still get the range needed.
OldGermanHeaps said:
Seen a few granny chargers melt sockets
This is because the use pattern often involves being active for several hours, which is only a problem if the plug or socket have a wiring fault which causes heat build up. Less of a problem for boiling a kettle, but can cause trouble if on for several hours. If you use a plug in charger, test the plug/socket for over heating after 1/2 hour.
As we do low mileage, a granny charger would work for us, and I could have saved a bundle on not having a wall box.
However, the sheer ease of use of the tethered wall box; it's just a one-handed operation to plug in when I get home or when I start my journey, makes the whole granny charger system just a complete mess.
OldGermanHeaps said:
Seen a few granny chargers melt sockets
Most quality oem granny chargers have a temperature sensor built into the 3 pin plug,it’s a last line of defence. It’s one of the reasons they specifically say not to use an extension lead. Will a knock off from Temu have the same, who knows. Can you get on a smart EV tarrif with your car and a granny charger?
I started off with a granny charger and Octopus Go for over a year, then had a Zappi charger installed.
Having the Zappi allowed me to switch to Octopus Intelligent Go (car not supported)
Low mileage means I didn't really need a proper charger, but the access to a cheaper tarrif makes it worthwhile. Not so much for the EV charging, but for the whole house it saves me over £200 a year.
I've got a heatpump and a 12KWh house battery, so can make full use of the lower off-peak rate and extra "bonus" slots. With gas/oil heating and no battery, it wouldn't make financial sense to pay for a charger.
I started off with a granny charger and Octopus Go for over a year, then had a Zappi charger installed.
Having the Zappi allowed me to switch to Octopus Intelligent Go (car not supported)
Low mileage means I didn't really need a proper charger, but the access to a cheaper tarrif makes it worthwhile. Not so much for the EV charging, but for the whole house it saves me over £200 a year.
I've got a heatpump and a 12KWh house battery, so can make full use of the lower off-peak rate and extra "bonus" slots. With gas/oil heating and no battery, it wouldn't make financial sense to pay for a charger.
OldGermanHeaps said:
Seen a few granny chargers melt sockets
I had a socket get a bit warm when granny charging a friend's EV. A standard domestic 13A extension lead was in use. I have since heard that using a standard extension lead can cause problems.Replaced the socket with a good quality one. When my own EV arrived and I was granny charging for the first month or so I made an extension lead using 2.5mm flex and good quality fittings and had no issues at all. Toughleads will sell you an EV-suitable extension lead.
Edited by this is my username on Thursday 5th February 09:07
this is my username said:
OldGermanHeaps said:
Seen a few granny chargers melt sockets
I had a socket get a bit warm when granny charging a friend's EV. A standard domestic 13A extension lead was in use. I have since heard that using a standard extension lead can cause problems.Replaced the socket with a good quality one. When my own EV arrived and I was granny charging for the first month or so I made an extension lead using 2.5mm flex and good quality fittings and had no issues at all. Toughleads will sell you an EV-suitable extension lead.
Edited by this is my username on Thursday 5th February 09:07
As above there's nothing wrong with using a 13amp granny charger, we used one as our only means of charging for about a year, but you need to be confident in the qualify of both the socket you're using and the wiring behind it. In fact unless you know its history, I'd probably replace the socket you intend to use with something decent quality just as a matter of precaution and while you're in there make sure it's on the ring not a spur and that the cabling is all 2.5mm cross-section.
Extension leads are fine, with the same caveat at the socket - it needs to both be decent quality and in good condition. Plenty of "13amp" extension leads are not actually up to prolonged use at 13amps. You really want one with 2.5mm cores (which are usually branded as "heavy duty" or similar.
Extension leads are fine, with the same caveat at the socket - it needs to both be decent quality and in good condition. Plenty of "13amp" extension leads are not actually up to prolonged use at 13amps. You really want one with 2.5mm cores (which are usually branded as "heavy duty" or similar.
Edited by kambites on Thursday 5th February 09:41
I've used a granny charger for just over a year now. We only use it about once a month due to the other half having a short commute. We run it off a cheap extension lead through to the garage under the door, then the charger back out of the door. Never had any issues at all. The socket gets lukewarm to the touch at the absolute most. That's a genuine Hyundai supplied charger though.
Speed is about 2.6-2.7kw so useable enough. Can take like 36 hours from the battery equivalent of fumes but an overnight charge or 2 is more then enough to hit 90% ish.
A firm local to me is offering a 7kw charger installed for a shade under £600 and it is tempting me but then I'd need permanent power in the garage which is more money, time and faff. I'll probably do it one day.
Speed is about 2.6-2.7kw so useable enough. Can take like 36 hours from the battery equivalent of fumes but an overnight charge or 2 is more then enough to hit 90% ish.
A firm local to me is offering a 7kw charger installed for a shade under £600 and it is tempting me but then I'd need permanent power in the garage which is more money, time and faff. I'll probably do it one day.
I used a granny charger for 3 years on a hybrid Audi with no issues. Easily charged enough overnight for the 30odd mile range it had. Now with a full EV got a 7kw installed (Vchrgd) - properly fused installation, and has a timer and remote access as the car doesn’t - works just fine.
I made do with 3-pin when I had a charger at my office. Since we moved, I don't and overnight on 3-pin made me anxious but also didn't add enough and left me short a couple of times making it a bit of a false economy then having to go to a public charger.
Since I had my Zappi installed it's been much easier. It's a relatively small cost in the grand scheme of things and is also future proofing yourself, I'd just do it.
Since I had my Zappi installed it's been much easier. It's a relatively small cost in the grand scheme of things and is also future proofing yourself, I'd just do it.
With regards to dodgy sockets & old wiring etc.
If I were to go down this route I'd have an EV rated external weatherproof socket installed outside the garage, coming off the garage circuit. The house is only 6yrs old, so relatively modern wiring/fuseboard etc, and the garage runs off it's own circuit, with just a chest freezer running overnight, so socket & wiring integrity should be fine. I'd initially run this with the supplied granny charger, then upgrading if I felt it necessary.
I'm still going to get a 7kw installation quote, just incase it's not as bad as I think, but with the meter box being where it is I don't think I'll see change from £600 labour, whereas I can get my mate to install the outside 3 pin for £50 and a pint
If I were to go down this route I'd have an EV rated external weatherproof socket installed outside the garage, coming off the garage circuit. The house is only 6yrs old, so relatively modern wiring/fuseboard etc, and the garage runs off it's own circuit, with just a chest freezer running overnight, so socket & wiring integrity should be fine. I'd initially run this with the supplied granny charger, then upgrading if I felt it necessary.
I'm still going to get a 7kw installation quote, just incase it's not as bad as I think, but with the meter box being where it is I don't think I'll see change from £600 labour, whereas I can get my mate to install the outside 3 pin for £50 and a pint
kambites said:
As above there's nothing wrong with using a 13amp granny charger, we used one as our only means of charging for about a year, but you need to be confident in the qualify of both the socket you're using and the wiring behind it. In fact unless you know its history, I'd probably replace the socket you intend to use with something decent quality just as a matter of precaution and while you're in there make sure it's on the ring not a spur and that the cabling is all 2.5mm cross-section.
Extension leads are fine, with the same caveat at the socket - it needs to both be decent quality and in good condition. Plenty of "13amp" extension leads are not actually up to prolonged use at 13amps. You really want one with 2.5mm cores (which are usually branded as "heavy duty" or similar.
An extension cable 'is' a spur. Extension leads are fine, with the same caveat at the socket - it needs to both be decent quality and in good condition. Plenty of "13amp" extension leads are not actually up to prolonged use at 13amps. You really want one with 2.5mm cores (which are usually branded as "heavy duty" or similar.
Edited by kambites on Thursday 5th February 09:41
There's nothing wrong with a spur as long as you don't overload it.
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