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Using trickle charging


Mar 5, 2020
Sorry, I was wrong on the number. For me charging at 32A gives 98% efficiency, at 10A is 88-92%

The difference is explained by the car being powered up while charging, which uses about 250W, a larger percentage of the 10A is therefore lost. If you are low mileage it won't add up to a lot of cost however.

Also worth noting that when pre-heating, the car pulls a little more power than a 32A can supply, so your battery can drop a little, on a 10A UMC you'll lose a lot more miles pre-heating.

If you look at Charging Connectors | Tesla UK you'll see the statement

Tesla recommends storing your Mobile Connector (6m) in the trunk of your car, to use as a backup charging solution when traveling.
I guess it's up to your own interpretation as to whether that gives you confidence to use it every day, they are expensive to replace once the warranty is done.

That efficiency matches my experience too monitored via Teslamate.
It works for me now especially via the cost of having a EVSE fitted.
There are 2 50kw chargers 5 minutes from my house if the worst came to it. Longer term though I can understand the investment will likely be worth it.

Glan gluaisne

Active Member
Supporting Member
Sep 11, 2019
I usually feel the plug when I unplug before heading for work. By that time it’s not actively charging. It is charging now (having just popped out to get the papers!). Went out to feel it and it is slightly warm but certainly not hot!

It should not be hot, as there is a temperature sensor inside the UMC moulded plug to shut the charge point down if the plug does get hot. It's a feature of all BS1363 plugs that they do get warm when passing a high current, as up to 1 W can be dissipated by a BS1362 fuse when in use. It's partially because of the heat generated by the fuse that BS1363 plugs tend to overheat on the line pin, an issue that can then lead to further overheating as the heat causes the spring contacts in the outlet to loosen slightly, increasing contact resistance and causing more heating.

It's very common to find the line side socket on outlets burned from this overheating during inspection, as shown in the photo below (taken from another EV forum where the charge point had caused the outlet to overheat). In fact it's so common, that I can almost guarantee finding signs of overheating during an EICR, especially on any installation that's more than about 15 to 20 years old. This is why it's very sensible to not only ensure that the periodic inspection for the installation is up to date (now called an EICR, due every ten years for non-rented domestic installations) but that all outlets used for heavy continuous loads are in good condition.


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