Most "granny chargers" use a normal 3 pin 13a socket but there is another option which may have advantages for some use cases. There is a class of 3 pin socket called "Commando" rated at 16 or 32a and you would therefore need to have a dedicated 40a fused outlet and cabling fitted but that may yet be a solution if (like me) you typically need to charge at several properties. In effect for your trouble you get a granny cable capable of up to 7 kw. Generally you will be able to select between 6 ,8,10,13,16 or 32A and many allow start of charging to be delayed by multiple hrs and at least one such "cable" has a wifi interface for remote monitoring.
Make sure that you get one that has a 10A setting as 13A could melt your sockets.
Most "granny chargers" use a normal 3 pin 13a socket but there is another option which may have advantages for some use cases. There is a class of 3 pin socket called "Commando" rated at 16 or 32a and you would therefore need to have a dedicated 40a fused outlet and cabling fitted but that may yet be a solution if (like me) you typically need to charge at several properties. In effect for your trouble you get a granny cable capable of up to 7 kw. Generally you will be able to select between 6 ,8,10,13,16 or 32A and many allow start of charging to be delayed by multiple hrs and at least one such "cable" has a wifi interface for remote monitoring.
Hi
This is the one I use. It lets you vary the charge 6A, 8A, 10A and 13A.
https://www.ebay.co.uk/itm/374582122592
Its quite handy to be able to vary the charge rate but they are more expensive than fixed rate chargers.
I charge on an economy 7 tariff and leave it on all night sometimes at a reduced rate if I just want a small "top up"
I have only had it a few weeks - so far its worked perfectly.