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I've just finished building my own 32A capable EVSE, but will be using at 16A until I change cars. However I thought I'd run it as a "Granny" charger for time being and have set it up for 12A.

After the first 2hr charge have checked currents and thermal increases of cables, DIN modules and most importantly the 13A plug.

Everything seems fine, so rather than dropping to 10A, I'm gonna stick with 12A. It should shave 45-60 mins off a full charge for me.

Anyone else regularly using 12A on their "Granny" charger?
IMG_20170421_214259.jpg
 

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I regularly use 11A in one particular location where the 13A socket I'm using is metal-clad, reasonably new, and in good condition - I get very little temperature rise on that setup.

Other locations have given me more temperature rise at lower currents.
 

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@arg yes any real temperature rise is down to quality of 13A plug and socket contracts. I emeried the pins on the plug I used and will only use a new quality socket .. :rolleyes:
I can certainly understand why all OEM stick to 10A for the "masses" ... :p or a measured 9.46A on my VW brick ..
 

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Not quite on topic, but I have used BS546 15A round pin plug and socket where a commando socket would not have been visually acceptable. Wired on its own circuit.

This was just inside the front door, most people thought it was standard 13a when they glanced at it. No internal fuse and good for 3.3 KW. Socket has shutters too.
 

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My DIY EVSE is switchable between 11A and 16A and has a blue commando plug. I then have two leads to convert from 13A and 32A commando over to the 16A commando on the EVSE.

I use 2.5mm flex to maximise heat dissipation from the plugtop and havent had any issues thus far running with that setup at 11A.

FWIW, my Merc brick was switchable between 8A and 13A. That did get pretty warm.
 

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My EVSE - not homemade - does 6 to 16a using a 16a commando plug for the supply.

I have been thinking about making a 32A adapter for it, but have not come up with a simple housing for the fuse. How did you do it?
 

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My homemade unit has a 20A RCBO inside it.

I guess the cable isnt fully protected though.

If you were really worried, you can probably squeeze a fuse holder inside the 32A connector. They're quite big.

Personally i'm not worried, a Dead short in the flex is likely to pop the upstream 32A fuse without issue, and theres no possible way a sustained 32A overload can be presented due to the RCBO.
 

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You can buy 32A commando extension leads made using 2.5mm2 cable. Never understood how that was acceptable for a commercial product?

Your 20A RCBO solves the problem tho.
 

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It depends what your doing. The regs are funny. For instance they allow fusing at the far end of a cable for overload protection.

IE, you can spur off a 32A ring main in 1.5mm T&E, so long as you run it to a FCU where its limited to 13A.

In a fault condition, ie someone hammering a nail thru the 1.5mm cable, its very unlikely the cable would fail before the upstream 32A fuse popped. And your covered against a continued overload causing the 1.5mm cable melting by the 13A fuse.

Its a similar story infact for the supply cable feeding your house itself. Theres a cable thats rated to say 100A, and a 100A fuse in the service head. But the cable in the ground is only protected by a much larger fuse or breaker upstream, despite only being 100A rated.
 

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All you say is true.

I would not trust that all users who pick up an extension cable fitted with 32A connectors and made using 20A? rated 2.5mm cable would think about ensuring 20A overload protection either up or down stream of the cable.

Not on my liability anyway.
 

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Biggest problem with running a lower current is relative loss of efficiency through the OBC.
At 2KW mines about 63% efficient and at 3.4KW it is about 75% the former is a lot more waiting time.
 
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