I could insult mine more than twice! Not sure if the next owner will though.
Sorry
Appollogee axsepted
Electric Vehicle charger installation
- Thread starter Tronco
- Start date
Appollogee axsepted
Some years ago a mobile cinema ( articulated lorry ) was parked on a car park for a public event. To avoid running the generator the local council supplied power from a lighting column. The problem then was how to get a ground rod through the concrete to "earth" the vehicle. The council could not provide an "earth" but insisted there was an earth to the vehicle's "ground" ( the chassis ). There was no "earth" point in the column, I assume it was it's own ground rod being several feet into the ground.
The solution was to move the vehicle closer to a flower bed and hope there were no services when a rod was driven in between the flowers.
The solution was to move the vehicle closer to a flower bed and hope there were no services when a rod was driven in between the flowers.
I'm not so sure - plenty of Class II garden equipment and some other tools 'enjoy' very rough treatment and neglect - and how many people get such things 'serviced' (as opposed to repaired) at all, let alone well, or when the items age? As you say, Bernard's point is valid, but I don't think it's in any way unique to electric cars.
Kind Regards, John
It does, at least in the context of an electric vehicle, and that would be consistent with rules/regs about caravans etc. but that difference between TN-S and TN-C-S has, AFAICS, got nothing to do with ensuring that a protective device will operate, has it? I'm a bit confused - that quote came from eric, who I'm sure "understands the different methods of ensuring protective devices will operate when a fault develops" at least as well as do you and I. As so often discussed, the only reason for distinguishing between TN-S and TN-C-S earthing systems is because of the tiny risk that a TN-C-S 'earth' could rise to a potential dangerously above that of true earth under certain fault conditions.
If one takes the view that a TN-C-S earth must not be used for this purpose, and if one does not know what type of supply one has then, indeed and of course, an earth rod is the only solution.
Indeed, from the safety point of view, having just the car body 'safe' (e.g. by being non-metallic') is not enough - all of the car's metal components would need to be isolated from the supply earth. However, no-one was suggesting that a fibreglass body would get rid of the safety issue - it arose as a 'rebuke' to the suggestion that the reason why EV manufacturers seem to see the need to have the car's body connected to earth was in order to provide EMC screening - something which fibreglass alone clearly wouldn't achieve!
Kind Regards, John
I meant the likelihood of a mechanic ensuring the Class II provisions were maintained, rather than the probability of failure of suc provisions. It's quite common for older vehicles to have protective covers removed and not replaced.
Surely only the accessible metallic parts would need to be isolated from the supply earth. If metal EV bodies are earthed for EMC reasons, there's no reason why earthed shields could not be fitted around the sensitive bits and the HF radiating bits, and then an insulating cover fitted around the shields.
Fair enough. However, as I said, I suspect that the risk of failure of the Class II features of other types of equipment may be at least as high as that risk. Who knows.
Kind Regards, John
Yes, of course - although if one is allowed to open the bonnet, there are not going to be many metallic parts which are not accessible.
Exactly - which is why I don't really buy EMC screening as the 'reason' (if there is a rational reason) for the metallic parts of a car (body and otherwise) having to be connected to the supply earth. It wouldn't surprise me if there is no particularly good reason at all.
Kind Regards, John
Certainly earthing the car body will have a major effect on the EMC. Separate shields cost money!
I can't think of any good reason.
The fact that the body may form part of the ELV circuitry within the vehicle is no reason why the earth of an LV supply to charging apparatus needs to be connected to it.
What Vauxhall Ampera are claiming is that it's impossible to build a Class II battery charger.
It's probably come about as a result of all those years of car designers and auto electricians etc referring to the body as "earth", when in fact it has never been anything of the sort.
I wonder what the ground-up (pun intended) design of the Tesla does?
The fact that the body may form part of the ELV circuitry within the vehicle is no reason why the earth of an LV supply to charging apparatus needs to be connected to it.
What Vauxhall Ampera are claiming is that it's impossible to build a Class II battery charger.
It's probably come about as a result of all those years of car designers and auto electricians etc referring to the body as "earth", when in fact it has never been anything of the sort.
I wonder what the ground-up (pun intended) design of the Tesla does?
Agreed. Certainly no electrical reason I can think of. Maybe a financial one or, as you go onto imply, just 'unthinking' convention/history.
They might not be claiming that it's impossible (which would clearly be nonsense), but they may think they have a reason for feeling that it is 'inappropriate', too costly or otherwise 'less practical'.
That wouldn't surprise me.
Kind Regards, John
Costly or not, BMW will presumably have to address that one with their upcoming non-earthable body!
Kind REgards, John
That's wrong. They are not claiming any such thing - they just confirmed that the car body was connected to the CPC of the circuit feeding the charging point.
They have not said that is was impossible to build a Class II battery charger.
"I would think it's something to do with the fact that the car body provides the -ve/ground connections for the car's internal electrical system and therefore it's not possible to make it double insulated." are MY words and in any case I'm referring to the car body, not the charger.
I have not taken much interest in electric cars as the idea of sitting on top of a 200 to 300 volt battery built from lithium compounds does not appeal to me. An accident in which damaged the battery could result in an electrical fire and shock hazard. ( The Dreamliner aircraft batteries were supposed to be super safe for aviation use ).
However I have now done a little bit of research.
From http://www.cenex.co.uk/programmes/plugged-in-midlands/charging-point-equipment
No wonder there is a "problem" of design and cost in making a charger.
To transfer 50 kW across an isolation barrier that can withstand over 600 volts in normal use will need a good design. The peak voltage across the isolation barrier is the battery positive at 300 volts and the mains negative peak of 339 volts making 639 volts.
However I have now done a little bit of research.
From http://www.cenex.co.uk/programmes/plugged-in-midlands/charging-point-equipment
No wonder there is a "problem" of design and cost in making a charger.
To transfer 50 kW across an isolation barrier that can withstand over 600 volts in normal use will need a good design. The peak voltage across the isolation barrier is the battery positive at 300 volts and the mains negative peak of 339 volts making 639 volts.
OK.
But it's the charger which is the problem - it's that which isn't, but could be, Class II.
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