13A EV chargers

Harry Macdonald: 
From an electrical safety point of view, I'm wondering why a portable EV charger is any different from a good old fashioned battery charger that we have been using for years. Balance it on the radiator and clip the leads to the battery.

We never bothered about earthing it then!

The CPC of a classical battery charger is not connected to the chassis of the vehicle. (Though one of the 12 V leads will be.)

The transformer in a traditional 12V battery charger is an iron cored thing running at 50Hz, and there is full isolation primary secondary, the new ones are double insulated.

The EV charging lead provides no such isolation - it is just a set of relay contacts  arranged to allow mains to reach the car or not depending on some signalling between it and the car. 

The actual charger - the bit that takes mains on one side and has the battery on the other, is built into the car, and is neither class 2 nor is the secondary side earth isolated.

Mike.

All of the so-called granny leads that I have seen in our workshop have thermal protection built in to the plug top. 
I have always considered that the risk of electric shock on EV roll out is minimal compared to the risk of fire.

Thanks Mike.

So an old metal cased battery charger sitting on the engine block carries just the same risks as an EV simply plugged in without PEN fault protection?

Harry Macdonald: 
So an old metal cased battery charger sitting on the engine block carries just the same risks as an EV simply plugged in without PEN fault protection?

With respect, that is a bit silly.

When I charge a flat battery, I generally remove it from the vehicle. Occasionally, I use my charger to start a car, but in that case, the duration is short and clearly loss of PEN would be obvious.

Harry Macdonald: 
 

Thanks Mike.

So an old metal cased battery charger sitting on the engine block carries just the same risks as an EV simply plugged in without PEN fault protection?

Even if it were the case, the two clearly do not carry the same risk.

The difference is that an EV is charged very frequently, whereas a vehicle starter battery is rarely charged from the mains.

gkenyon: 
 

Harry Macdonald: 
 

Thanks Mike.

So an old metal cased battery charger sitting on the engine block carries just the same risks as an EV simply plugged in without PEN fault protection?

Even if it were the case, the two clearly do not carry the same risk.

The difference is that an EV is charged very frequently, whereas a vehicle starter battery is rarely charged from the mains.

The same as touching a metal outdoor tap connected to a PME system, outdoor lighting, heaters, hot tubs on PME. There is risk associated with it all. 
 

A 32A portable EV charger with the correct plugs (cee) is surely only a risk IF a pen fault occurs? These fixed installed chargers with built in protection that negate the need for rods don’t protect against voltage potentials between local earth and the supplier earth. 

The 13A variants do pose a risk due to contacts etc, but dedicated EV outlets with 13A sockets are OK for occasional use surely? There are various manufacturers who make 13A outlets specifically for EV chargers. 

vantech: 
 The same as touching a metal outdoor tap connected to a PME system, outdoor lighting, heaters, hot tubs on PME. There is risk associated with it all. 

The difference is, the ESQCR specifically mentions a prohibition for caravans and boats being connected to PME earthing arrangement, and the DTI guidance on the ESQCR says this is because of the safety issue (see Page 20). The issue is perhaps whether you want to stick your neck out and try to differentiate a mobile & transportable unit (717) and a caravan (721 and 708) and an EV on charge (722).

gkenyon: 
 

vantech: 
 

The same as touching a metal outdoor tap connected to a PME system, outdoor lighting, heaters, hot tubs on PME. There is risk associated with it all. 

The difference is, the ESQCR specifically mentions a prohibition for caravans and boats being connected to PME earthing arrangement. The issue is perhaps whether you want to stick your neck out and try to differentiate a mobile & transportable unit (717) and a caravan (721 and 708) and an EV on charge (722).

BS7681 has no control over portable equipment, including EV chargers. You could argue the intended use for the socket I suppose, but that would only apply to a dedicated (and labelled?) outlet.

So, yes, there's not a lot BS 7671 can do regarding people using a standard socket-outlet in a PME installation to supply a caravan or EV, as a lot of people do, except say it shouldn't be done and recommend suitable precautions are taken as in 722.411.4.1. 

However, BS 7671 can't contradict legislation, particularly given the DTI guidance (see Page 20).

I think the moral being just because you can, doesn't mean you should.