Electric vehicles

[Spectric]

By using power line communication, where you can use the mains to carry data by superimposing it onto the Ac.

 

[selectortone]

The chargepoint also supplied 1kHz PWM signal that indicates to the charging system (in the car) his much current is available. The PWM signal goes negative and positive with respect to ground. I imagine this provides a bit more safety, being slightly more complex than a positive only waveform.

From what the installation guy told me, the chargepoint is clever enough to reduce the current available to the car (or tell the car to reduce demand? One of the two...) if there is a significant demand elsewhere in the house - for example if the washing machine and the power shower are on at the same time and I go out to the workshop and start using my lathe or whatever.

 

[John Brown]

By using power line communication, where you can use the mains to carry data by superimposing it onto the Ac.

Well of course, but you said "for the EV to determine how much", which is not the same thing. Power line signalling is the EV being told how much power is available.

 

[Just4Fun]

There is also a safeguard against you driving off while plugged in, which a standard mains plug wouldn't provide.

Why not?
I would have thought the car would detect that the cable is connected and disable the drive system until it is unplugged. What would be needed outside the car?

 

[John Brown]

From what the installation guy told me, the chargepoint is clever enough to reduce the current available to the car if there is a significant demand elsewhere in the house - for example if the washing machine and the power shower are on at the same time and I go out to the workshop and switch my latge on.

Some are, some aren't. If they are, then they need to be able to measure that loading, usually with a current transformer.
There may be units that communicate with smart meters, as in Spectric's original assumption, but I doubt it.

 

[John Brown]

Why not?
I would have thought the car would detect that the cable is connected and disable the drive system until it is unplugged. What would be needed outside the car?

The cable could be connected at the car end, but disconnected or turned off at the other end.

 

[John Brown]

The other point to consider is that the EV applies a load to the 1kHz pilot signal (IIRC), which tells the power supply to switch the mains through. That way the plug doesn't become live until is all plugged together. There are mechanical switches as well, when you press the lever to detach the plug from the EV.


Somebody thought about it a bit, I suppose, instead of just saying "let's just stuff a kettle plug into the end of a cable".

 

[pe2dave]

This thread is becoming rather 'points scoring' don't you think?

 

[John Brown]

Sorry, I was just attempting to explain how EVSEs work, and people keep asking questions.
It's all there on Wikipedia, folks fill your boots with J1772.
I'll shut up now.

 

[MikeK]

There is also a safeguard against you driving off while plugged in, which a standard mains plug wouldn't provide.

I didn't go to EV Charging System Cable and Port Design school, but all of the EVs I've seen have doors that have to be opened to access the car's charging port. A sensor on the door should easily determine if the door is open, whether or not a cable of any type is attached. I think my friend's Audi had a warning lamp on the dash if she didn't close the fuel door.

 

[John Brown]

I didn't go to EV Charging System Cable and Port Design school, but all of the EVs I've seen have doors that have to be opened to access the car's charging port. A sensor on the door should easily determine if the door is open, whether or not a cable of any type is attached. I think my friend's Audi had a warning lamp on the dash if she didn't close the fuel door.

Since you're actually addressing me, I'll temporarily un-shut up.
Yes, our PHEV has a sensor on the door as well. I guess the designers thought the electrical connection in the plug and socket would be more reliable. Our PHEV lets you drive off with the door open, but does warn you.
But I didn't write the spec.

 

[morqthana]

Interesting. How dou you think the EV might determine available current from a 3 wire mains feed?

Disclaimer - I've not rewound to find the start of the sub-discussion on charge point management.

But surely an on-board charger designed to plug into a regular domestic socket wouldn't do any determination of "available" current. It would manage the back-end output to ensure the batteries were looked after, but the front would basically be a switch mode power supply, designed to draw at most 13A in the UK and 16A sur le continent? Probably less, actually, to avoid loading outlets at the max supported for extended periods.

If the response to my "Disclaimer" is "That's obvious. You should have.", apologies.

 

[morqthana]

I think that for any serious fast charger you will need three phase, that can be a lot more than £900 and we must not forget that the electrical distribution system that supplies many housing estates will not have been designed to handle a large proportion of them charging electric vehicles. This issue will continue back up the grid with each supply point potentially being stretched to it's limits.

Well you can go to 14.5kW with a single-phase supply (63A circuit).

I read somewhere once that some DNOs are now installing 125A single-phase domestic supplies, but where they are with their diversity assumptions at the 11k/400 distribution substation level IHNI.

 

[morqthana]

I will miss ice cars though esp V8!

They can sound great

 

[Spectric]

Yes but a single load, you have to sum all loads, resistive loads can be larger but reactive are limited, hence why you cannot power larger machinery from an inverter and have to use a convertor. If upgrading a supply then you would go three phase, solves many issues and helps balance the grid.

 

[johna.clements]

Disclaimer - I've not rewound to find the start of the sub-discussion on charge point management.

But surely an on-board charger designed to plug into a regular domestic socket wouldn't do any determination of "available" current. It would manage the back-end output to ensure the batteries were looked after, but the front would basically be a switch mode power supply, designed to draw at most 13A in the UK and 16A sur le continent? Probably less, actually, to avoid loading outlets at the max supported for extended periods.

If the response to my "Disclaimer" is "That's obvious. You should have.", apologies.

I am not sure who started it but in a reply i stated that you could measuer what other devices were using so that the car does not over load the house circuits. this could be done with a simple electrical mechanical device.

 

[morqthana]

No it is not. Reproduction is the solution.
The greater the population the more likely the chance of survivors when things go pear shaped.
It's nature's way - individuals don't matter and are disposable, as long as there are survivors
It's common throughout the living world that stressed populations have strategies to survive. The first organism you learn about at school is the amoeba. When things are OK they reproduce steadily by budding, when the pond dries up they "encyst" and subdivide many times over. Come wetter weather and the cyst expands breaks up and there's millions of the little boogers.
Works similarly with **** sapiens, destabilised societies (e.g. war etc) tend to reproduce more. Stable societies even have falling populations causing them anxiety.
Think on!

If what I heard once is true we should be seeing a skew towards more girls/fewer boys being born. Stress does that, because at a population level increasing stress coud be a sign of impending population-level catastrophe, and if a population is to recover from a massive de-populating situation you need more women than men.

 

[Spectric]

this could be done with a simple electrical mechanical device.

I have worked on projects where motor control panels were linked so contactors would be inhibited so you could not run all six 100Kw motors simultanously because a) there was no need and b) the supply was only 620 amps.

 

[morqthana]

Yes but a single load, you have to sum all loads, resistive loads can be larger but reactive are limited, hence why you cannot power larger machinery from an inverter and have to use a convertor. If upgrading a supply then you would go three phase, solves many issues and helps balance the grid.

Yes - I was forgetting that SMPSUs aren't resistive, but you ought to be able to get to a .95 power factor.

And anyway - a street of houses taken as a whole is a 3-phase load....

 

[morqthana]

I believe that you know when you have lost EV power as the car seems to lose power as it reverts to it's 1.5 litre engine.

See if you can lay your hands on a BMW M12/13 1.5l engine...