mgboyes
Member
Personally, I use an external, weatherised 13A socket with a portable EVSE (PEVSE) - or Granny charger - for charging my MS (and another one for my i-MiEV, for that matter) a home made one, as it happens. I am firmly of the opinion that the dedicated domestic EVSEs (as funded) by HMG are largely unnecessary and the money could be far better used for a proper rapid charger infrastructure for use by those EVers not fortunate enough to be able to afford a Tesla (but us Tesla owners too, of course).
If you do lots of miles, then sure, a 30A EVSE is worth it (or one with even more power, if needs be). Just bear in mind that you can still do 6MRHC (6 miles of range per hour of charging) on a 13A socket with one of these, enough of an overnight charge for double the average UK daily mileage. PEVSEs only pull 10A so as to not overload the plug/socket. Just be sure to check the plug and socket for heating once in a blue moon and ideally, leave the PEVSE always connected. This will prevent wear on the mating contact surfaces which leads to a poor connection, which leads to increased resistance between the contact surfaces, which leads to more heating, more resistance, more heat... Not good. The relevant British Standard for plugs (BS1363) says about 50 degrees C is the maximum working temperature for plugs - but they should still be 'operational' at 70C. The thermal due above blows at 72C.
Aside from building your own PEVSE (for about £250 or less), they come up on eBay quite regularly and both Type 2 and Type 1 PEVSEs (so all of them, basically) are electronically compatible with the MS. However, the Type 1 plug (and therefore cable as the plug is normally crimped onto the cable with a hydraulic crimping tool) will have to be replaced with a Type 2 plug (3m replacement cable&plug set is £99 at EVBitz) and is a relatively simple job for the competent DIYer (but should, of course, be checked by a 'qualified person' before use). Longer ones can also be bought as can a special, short 3P, 32A T2>T2 cable as well as other T2 cables, EPCs, plug 'holsters' and other charging bits and bobs.
If your PEVSE does not have 13A plug thermal management already built-in, I would also advocate the use of a thermal fuse wired in series with the live wire inside the plug to protect the installation in the event of the plug overheating due to the above. This is very simple, effective and cheap (£1) insurance against plug over-heating issues. MW (Director of EVBitz.uk)
Sorry I cannot recommend any of that. A 13A UK plug is not well suited to permanent EV charging, and I can't think of any sane reason to spend £300 on a DIY solution designed around a 3 pin socket in preference to paying £300 to have a professional installer fit a properly designed and tested 32A charge point.
Also 10A charging is inefficient, so as well as being slower it is more expensive because a greater proportion of the energy is wasted in the charging process. With the Model S the inefficiency is not so bad (though it is there), but with other cars it's very significant indeed (originally it was so bad on the Renault Zoe that it could not charge at all below 16A).
And given that there's only a 7 hour offpeak charging window in Economy 7 then 10A charging really doesn't get you that much charge - about 40 miles of typical range per day.
And in Winter in particular the remote cabin pre-heating can easily draw 7kW, so where a proper charge point will allow the car to heat itself up from the mains, a 10A slow EVSE will not be able to keep up so you end up discharging the battery to warm the car.
The OP implies they're going to do about 500 miles a week, in which case 10A charging cannot keep up with their charging needs if they want to charge only during offpeak hours.
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