Granny Charging

[Captainfieldmouse]

For various reasons I won’t go into now the only way I can charge my HS PHEV at home is to use a 3 pin granny charger. This is absolutely fine as a 20 kWh charge can be done overnight. However I’m only getting around 2.4 kW charging whereas I was expecting closer to 3.3 kW. Charger is set to 13 amp. My spark installed an EV rated outdoor socket so should be getting a faster charge rate than I am. Or have I missed something?

 

[salty]

That sounds about right, for a Granny.
I'm sure others will be along soon.

 

[Speakasyoufind]

Hi. I have the previous version, but I can tell you now, 10amp is max for prolonged periods of use, even for an ev rated socket.
I tried mine (charger) set to 13amp and it was fine for a short while but it soon burnt the 13 A fuse out and damaged the EV rated socket itself (burnt and bubbled surface). Replaced fuse, reduced to 10 amp (2.4 kW approx.) and it has been fine since, several months use and used every night, not a hint of burning to the surface of the plug or socket.
So whilst it is capable of hitting 3.4 kW approx at 13 amps, the socket will not stand it, nor the charger, in my experience. So please stick to 10 amps and 2.4 kW charge rate

 

[Lovemyev]

Some after market Granny units can be adjustable to provide a higher rate of charge, but OEM units tends to air on the side of safety & caution.
This is to prevent the chance of producing too much heat at both the socket outlet & three pin plug.
Also when you provide a Granny charger to a new owner, the manufacture has absolutely no idea of the condition / age of the electrics that different people are using in their homes.
The age of the property has no clear relevance really, as the property could be 80 years old, but has been rewired to the latest spec's etc.
The increase in charging speed between 10 amps and 13 amps gained, is marginal and not worth the risk of the extra strain on the system long term.

 

[Captainfieldmouse]

Hi. I have the previous version, but I can tell you now, 10amp is max for prolonged periods of use, even for an ev rated socket.
I tried mine (charger) set to 13amp and it was fine for a short while but it soon burnt the 13 A fuse out and damaged the EV rated socket itself (burnt and bubbled surface). Replaced fuse, reduced to 10 amp (2.4 kW approx.) and it has been fine since, several months use and used every night, not a hint of burning to the surface of the plug or socket.
So whilst it is capable of hitting 3.4 kW approx at 13 amps, the socket will not stand it, nor the charger, in my experience. So please stick to 10 amps and 2.4 kW charge rate

Thanks! My external socket is EV rated and is specifically designed for max kw charging. Electrician showed me the max output on a tester and it was up to 3.4kw. Can’t help thinking it’s at the car end of things?

Some after market Granny units can be adjustable to provide a higher rate of charge, but OEM units tends to air on the side of safety & caution.
This is to prevent the chance of producing too much heat at both the socket outlet & three pin plug.
Also when you provide a Granny charger to a new owner, the manufacture has absolutely no idea of the condition / age of the electrics that different people are using in their homes.
The age of the property has no clear relevance really, as the property could be 80 years old, but has been rewired to the latest spec's etc.
The increase in charging speed between 10 amps and 13 amps gained, is marginal and not worth the risk of the extra strain on the system long term.

Thanks. My electrician upgraded my MCB only 6 months ago and he assured me that my domestic wiring could definitely handle the full 13a. The granny charger is set to 13a and it stays that way through charging without reducing to 10 or 6a. My external socket is EV rated too so shouldn’t be an issue.
It’s not a showstopper as I still get a full charge overnight, but it would be good if I could get a ‘top-up’ charge slightly quicker during the day

 

[EvTek23]

I think it also depends where you are seeing the 2.4kW. Is this on the Granny charger display i.e. power going into the vehicle, or on the infotainment screen on the charging tab, as that will show what is going into the battery. The difference will be the CCU losses inherent in all systems.

 

[Captainfieldmouse]

Good shout, hadn’t considered that. The granny charger hovers around 2.8 to 3 kw, the MG app around 2.4kw. Never sat in the car whilst charging as normally done overnight, but will check next time. Thanks again

 

[EvTek23]

@Captainfieldmouse, that's very similar to mine, the charger will say 2.3kW and the app says 1.9kW

 

[Captainfieldmouse]

@Captainfieldmouse, that's very similar to mine, the charger will say 2.3kW and the app says 1.9kW

So which one do you think is right?

 

[EvTek23]

I think they'll both be right. The granny charger shows the total input power to the car, while the app shows the power at some point within the car, I'm not quite sure where. I thought this would be what is being delivered to the battery. I however found a third figure that was showing on the infotainment screen.
So the full readings I get while on charge are:
Granny charger 2.3kW,
App 1.9kW
Infotainment 1.5kW.
It could be that the infotainment reading is taken within the HV battery itself, while the app reading is from the CCU

 

[Julian Edwards]

For various reasons I won’t go into now the only way I can charge my HS PHEV at home is to use a 3 pin granny charger. This is absolutely fine as a 20 kWh charge can be done overnight. However I’m only getting around 2.4 kW charging whereas I was expecting closer to 3.3 kW. Charger is set to 13 amp. My spark installed an EV rated outdoor socket so should be getting a faster charge rate than I am. Or have I missed something?

A thee pin granny charger is usually 10 amps in the UK (240 x 10=2.4kW) . Although a domestic mains socket is 13amp, it will overheat if usud flat out for a long period. You can get slightly better if you run a dedicated 16 amp commando socket and purchase a 16 amp portable charger. You will find 13 amp granny chargers for sale, but I would advise against using one with a UK square pin plug. The 16 amp commando plug and socket is designed to carry full load constantly, the UK 13 amp is not. The MG charger is 10 amp for this reason.

 

[mikgle]

For various reasons I won’t go into now the only way I can charge my HS PHEV at home is to use a 3 pin granny charger. This is absolutely fine as a 20 kWh charge can be done overnight. However I’m only getting around 2.4 kW charging whereas I was expecting closer to 3.3 kW. Charger is set to 13 amp. My spark installed an EV rated outdoor socket so should be getting a faster charge rate than I am. Or have I missed something?

Car will only take 10A on a granny charger. It's designed to because of the extended duration. Despite whatever power is being measured at the socket there will be charging losses at the car end particularly when using granny charger as a % of power being drawn.

 

[mikgle]

Car will only take 10A on a granny charger. It's designed to because of the extended duration. Despite whatever power is being measured at the socket there will be charging losses at the car end particularly when using granny charger as a % of power being drawn.

And the so called EV socket doesn't provide any more power, its just a (supposedly) more robust socket to combat over heating. In my experience its best to use a switchless socket.

 

[Bob A]

Thanks! My external socket is EV rated and is specifically designed for max kw charging. Electrician showed me the max output on a tester and it was up to 3.4kw. Can’t help thinking it’s at the car end of things?


Thanks. My electrician upgraded my MCB only 6 months ago and he assured me that my domestic wiring could definitely handle the full 13a. The granny charger is set to 13a and it stays that way through charging without reducing to 10 or 6a. My external socket is EV rated too so shouldn’t be an issue.
It’s not a showstopper as I still get a full charge overnight, but it would be good if I could get a ‘top-up’ charge slightly quicker during the day

Like a few previous comments, I would err on the safety side having fortunately caught my attempt at using my granny charger at 13 amp before it set fire to my extension and possibly my garage.
The cable from my extension was in the process of melting and fortunately the RFD tripped out before further damage could be done.
I do use 13 amp while at work plugging into outlets that are higher rated than my home outlets.
Again, be safe and err on the lower amperage.

 

[mikgle]

Like a few previous comments, I would err on the safety side having fortunately caught my attempt at using my granny charger at 13 amp before it set fire to my extension and possibly my garage.
The cable from my extension was in the process of melting and fortunately the RFD tripped out before further damage could be done.
I do use 13 amp while at work plugging into outlets that are higher rated than my home outlets.
Again, be safe and err on the lower amperage.

Shouldn't be using extension lead..

 

[tazlaw69]

Well, I only use my 'granny' charger, as to have a full blown charger fitted costs an arm and a leg. I tried mine at 13 amp once and as soon as my heating kicked in it tripped the main outside fuse box. So now I only use 10 which takes about 6/7 hours from a low charge, but as I have all night it's not an issue. The only problem I have now is that after some 9 months of use the highest kilometers I get on a full charge is 98k!

 

[Bob A]

Shouldn't be using extension lead..

Too true but length of cable on my granny charger is too short. I have since purchased a charger with a much longer lead but the cable from the charger doesn't give me confidence that it would be any better than my extension cable (it's quite thin).
Again erring on the safety side, I stick to 10 amps with my new charger.
I do take your point about my use of an extension cable. My thanks.

 

[mikgle]

Well, I only use my 'granny' charger, as to have a full blown charger fitted costs an arm and a leg. I tried mine at 13 amp once and as soon as my heating kicked in it tripped the main outside fuse box. So now I only use 10 which takes about 6/7 hours from a low charge, but as I have all night it's not an issue. The only problem I have now is that after some 9 months of use the highest kilometers I get on a full charge is 98k!

You'd be better off to get an electrician to run a dedicated circuit to an outside ev socket or even a 16A commando socket, if your fusebox can take it. He would advise. Materials for this are quite cheap, depending how far the new spur would have to run to. Armoured cable, even 6mm² is only about £4/metre.