Granny charging

[Jomarkh]

What granny charger did you get?

Recently used a 10m 2.5mm ext lead and got 1.9kw. The 45m 2.5mm ext reel gave 1.7kw before tripping the thermal cut out

Hi, did you unwind it fully before using it?

 

[gbrspratt]

What granny charger did you get?

Recently used a 10m 2.5mm² ext lead and got 1.9kW. The 45m 2.5mm² ext reel gave 1.7kW before tripping the thermal cut out

Sorry for the late reply, I bought this: Amazon link

I use. Tough leads 10m extension too

 

[Berkofix]

No worries. Got a weatherproof plug housing and made one from a worn out extension reel.

Hi, did you unwind it fully before using it?

No, I kinda knew it might fail. I had brought several leads to try. I guess the main clue was written on the side of the reel, giving wattage ratings for wound and unwound. The granny charger has a temp sensor in its plug, I was curious to see the failure state. In the end the thermal trip on the reel kicked in first. In theory the granny charger should charge at 10 amps, so 2.3kW ish however depending on the cable I saw 1.9kW or 1.7kW (indicated on the iSmart app).

 

[Peterboat]

UK rated granny EVSE units are usually 10A 2.2kW. If you buy from Ebay or Amazon you can get them at 13A but they will cook the plug or/and socket if on for hours. Heaters etc. are not run continuously as they turn off and on when they reach the set temperature.

I fitted a 16 amp commando socket, twin pole switched, we use it for other things so it's not wasted and it doesn't overheat

 

[stevegus]

There are EV rated sockets with integral RCD that you can get from screwfix and the like.

For the brave “Granny chargers” on Amazon can come as big as 32 amps, which need a 32A “commando” type outlet and a suitable electrician installation.

 

[Coulomb]

In theory the granny charger should charge at 10amps, so 2.3kw ish however depending on the cable I saw 1.9kw or 1.7kw (indicated on the iSmart app)

The iSmart app reports the same as the car, which is net power into the battery after on-board charging losses and 12V loads. That will account for several hundred watts of discrepancy, so you really don't know how much loss is from the extension cord.

 

[Berkofix]

I was curious to see the loss rates, hence used a 45m and 15m 2.5mm² multi-strand extension cord. I do have a bit of 6mm² T+E so could make a lower loss ext lead, however the 20amp UK ring main it's fed from is based on a 2.5mm² Twin and earth ring not a 32amp 6mm² radial.

In the end the Zappi wall charger runs off a 6mm² radial, so the extension lead was an experiment whilst we were staying at an AirBnB.

 

[Everest]

however the 20amp UK ring main its fed from is based on a 2.5mm Twin and earth ring not a 32amp 6mm radial.

I'm not a sparky, but a standard UK ring final will generally support a max current of 32A when wired with 2.5mm² T&E. Unless there are specific reasons for de-rating (e.g. covering a floor area greater than 100m² or a cable length > 100m) then the ring final would normally be protected with a 32A MCB.

 

[stevegus]

Everest, you are absolutely correct that a ring main is 32amps total capacity.

Because its a ring you effectively have TWO 2.5mm feeds (albiet of unequal run length) to any given point on the ring

 

[Berkofix]

I'm not a sparky, but a standard UK ring final will generally support a max current of 32A when wired with 2.5mm T&E. Unless there are specific reasons for de-rating (e.g. covering a floor area greater than 100m2 or a cable length > 100m) then the ring final would normally be protected with a 32A MCB.

My certifying electrician encouraged me to de-rate the 32amp circuits to 20. Has been fine.

 

[Everest]

My certifying electrician encouraged me to de-rate to the 32amp circuits to 20

That's very unusual - why was that? Cable length, multiple circuits running in close proximity or excess insulation around the cable or something else?

 

[Berkofix]

All of the above for a refurb.

I'd imagine its a useful mitigation of risk for the certifying authority.

Its never been an issue, even on the kitchen circuit which you'd think might have a higher draw.

 

[Thumbsup]

I installed a tough leads extension lead on the outside of my garage. Instead of plugging it into the socket in the garage, it's wired directly in to a socket (I await the comments). First week I used the MG supplied charger but that only inputs about 1.7kW. After lots of research I bought a second granny charger that inputs 2.7kW. I have checked after it being on charge for 8 hours and nothing is warm let alone hot!

I have also switched to tomato energy. 13p from 10pm until 0000 and 5p from 0000 to 0600.

Approx 40 miles a day.

What is the brand of your “second” granny charger. That extra power would make a big difference in charging time.

 

[Mark Hewitt]

What is the brand of your “second” granny charger. That extra power would make a big difference in charging time.

I suspect they switched to one running at 13A. Given the weak point in a 3-pin setup is the socket and they aren't using that then I wouldn't know about the safety therein.

 

[Thumbsup]

My granny charger, supplied by MG for my MG4 essence, works well from a normal power point but only gives me 1.5 W. I mainly charge it with my excess solar during the day.
I do not want to install a dedicated charger. Is there someway I can increase the output from either my MG charger or a third-party charger?
15amp socket? 3 phase? ( I have access)
Bearing in mind I only get around 4kw solar.
I live in Queensland so we generally do get quite a bit of solar during the day
Thanks for any comments!

 

[ReintjeWA]

My granny charger, supplied by MG for my MG4 essence, works well from a normal power point but only gives me 1.5 W. I mainly charge it with my excess solar during the day.
I do not want to install a dedicated charger. Is there someway I can increase the output from either my MG charger or a third-party charger?
15amp socket? 3 phase? ( I have access)
Bearing in mind I only get around 4kw solar.
I live in Queensland so we generally do get quite a bit of solar during the day
Thanks for any comments!

There are some chargers on Amazon that will do closer to 2kW on 10amp sockets, and also do 15amp sockets which they claim will go up to 3 or 3.5 kW. I'm using one on a 10 amp socket for the time being and get max 1.9 kW at the car. The next house will have a 15 amp socket in the carport, and eventually dedicated EVSE, but for the short commute I have at the moment this charger works pretty sweet. We went for the 10m cable because we actually run it down form the balcony to ground level to charge.

EV Charger Type 2 [3.5 kW, 10M, 10A to 15A Adapter] dé Portable EV Chargers with Australian 15A Charger EV, Adjustable Current Compatible with Tesla Model Y/3, BYD/MG/Polestar/Kia and Other PHEV/BEV : Amazon.com.au: Automotive

EV Charger Type 2 [3.5 kW, 10M, 10A to 15A Adapter] dé Portable EV Chargers with Australian 15A Charger EV, Adjustable Current Compatible with Tesla Model Y/3, BYD/MG/Polestar/Kia and Other PHEV/BEV : Amazon.com.au: Automotive

www.amazon.com.au

The nice thing with this charger is that it detects what amp socket you're using, so no risk in blowing your fuse (apparently some chargers you have to set the A every time).

 

[Everest]

There are some chargers on Amazon that will do closer to 2kW on 10amp sockets

What voltage do you have down under? I would have thought a 10A charger would deliver 2.3kW to the vehicle - or is the 2kW, that you are referring to, the power into the HV battery, rather than power to vehicle?

 

[ReintjeWA]

I think it should hover around 240v, I don’t know the exact range, but the charger often shows a bit above 240. The charger shows just above 2 kW, but the car (app) shows 1.9kW going into the HV.

The official MG granny charger we get here only puts something like 1.5 kW in the HV on 10 amps, I guess they’ve build in something to keep it lower, but I don’t know enough about sparky things.

 

[Everest]

Sounds like the official charger is running at 8A then. That would equate to just over 1800W to the car, putting about 1500W into the battery with 300W of overhead / losses.

In the UK, the max continuous current for a non-EV rated BS1363 plug/socket is 8A, so that sort of makes sense to keep things safe for all possibly situations.

 

[siteguru]

Over here we have a 13A ring main circuit, but the granny charger will only deliver a maximum of 10A. On a nominal 230V supply that's 2.3kW ... but that also has to service all the loads plus charging losses.

I don't have a current clamp so I don't know what my MG granny actually delivers, but I do know that approx. 1.8kW charge rate is what goes into the battery (according to iSmart).