How Wireless EV Charging Works

[bernardgreen]

Back onto the topic, an update on wireless charging methods

https://eepower.com/news/can-tesla-lead-the-pack-to-wireless-ev-charging/?

 

[ericmark]

That will remove the trip hazard of the charging lead, but can't see how it will speed up charging.

 

[Harry Bloomfield]

That will remove the trip hazard of the charging lead, but can't see how it will speed up charging.

Or how it can be sufficiently efficient, to make it worthwhile. The losses will be tremendous.

 

[ericmark]

Or how it can be sufficiently efficient, to make it worthwhile. The losses will be tremendous.

Will it also charge my watch, or in some cases phones?

 

[JohnW2]

Or how it can be sufficiently efficient, to make it worthwhile. The losses will be tremendous.

As I've said before (and attracted some flak , I don't think it's true 'efficiency' that you're talking about but, rather 'effectiveness'.

As I've said, inductive coupling can be useless as a means of effectively transferring electrical energy, but nevertheless n may be very 'efficient'.

 

[Harry Bloomfield]

As I've said before (and attracted some flak , I don't think it's true 'efficiency' that you're talking about but, rather 'effectiveness'.

No, I really meant 'losses', energy just wasted, heating the environment, the surroundings, and the vehicle chassis due to eddy currents.

 

[JohnW2]

No, I really meant 'losses', energy just wasted, heating the environment, the surroundings, and the vehicle chassis due to eddy currents.

As I keep saying, there are not necessarily any major 'losses' (wasted energy) - which, if present, would represent true 'efficiency problems'.

However a system of inductive coupling can be very ineffective (very little energy transferred, hence very 'slow') without there being appreciable 'losses' (i.e. 'poor efficiency'). In the real world, there will obviously always be some actual losses (hence less than 100%efficiency),but not necessarily very much.

 

[DetlefSchmitz]

I don't think it's true 'efficiency' that you're talking about but, rather 'effectiveness'.

No, I really meant 'losses', energy just wasted, heating the environment, the surroundings, and the vehicle chassis due to eddy currents.

He's strawmanning again.

 

[JohnW2]

He's strawmanning again.

I didn't understand why you said that the first time, and nor do I understand why you have repeated.

As you quoted, Harry referred to " 'losses', energy just wasted, heating the environment" - which, if it occurred, would indeed be an indicator of poor efficiency. However, as I keep saying, yet no-one seems to understand, 'ineffective' transfer of energy by (weak) inductive coupling does NOT necessarily have to be associated with such losses/wastage (i.e. poor efficiency, in the true meaning of the word).

To cite a sort-of analogy, a power source capable of providing only a few mA, but at an appropriate voltage, would be a very 'ineffective' way of charging a car battery (since it would 'take forever' to charge the battery) but that doesn't mean that it couldn't be very 'efficient'.

I'm used to people here being quite upset by the incorrect use of terminology, which is why I pointed out that people appeared to be using the words 'efficient' and 'efficiency' to refer to things other than what those words actually mean. The energy transferprocess we've been talking about may,of course, in some cases be inefficient as well as 'ineffective', but that is not necessarily the case.

 

[morqthana]

I'm used to people here being quite upset by the incorrect use of terminology,

And by the correct use it seems.

The energy transferprocess we've been talking about may,of course, in some cases be inefficient as well as 'ineffective', but that is not necessarily the case.

Or inefficient but effective.

 

[JohnW2]

And by the correct use it seems.

It rather seems so

Or inefficient but effective.

Perhaps, but that gets a little more complicated, since some people would probably say that 'effective' encompasses at least some degree of 'efficient' - i.e. a power transfer system might be 'effective' in the sense that it delivered the required amount of energy to the load, but if it were very inefficient, such that a lot of supplied power was 'wasted', rather than transferred to the load, some might well question whether it really was an 'effective' (or, at least, sensible!) way of doing things.

 

[DetlefSchmitz]

I didn't understand why you said that the first time

You start out by telling people who discuss percentage efficiency of wireless car charging that they are are really talking about something different that you can't define, that might be the rate of transfer of power compared with some imagined ideal. Then you tell them that because they are not talking about real efficiency they are talking nonsense. So you are telling people that they are claiming something different to what they are talking about and then telling them that they are wrong. All the discussion that mention an efficiency percentage has been about exactly that. Only you introduced the strawman of rate of charging up a car or whatever it is you are talking about. That would not be measured in %, as it would have some element of time in its measurement, like % charge/ hour, or some such. I would be interested in your evidence that I was lying when I said I was referring to absolute efficiency.

Speed of charging is clearly important, but what was being discussed was, as I said before, how much power gets wasted, as the net amount of power that will be used by cars will be a significant proportion of the country's generated power, so the waste will also be significant.

 

[JohnW2]

Speed of charging is clearly important, but what was being discussed was, as I said before, how much power gets wasted, as the net amount of power that will be used by cars will be a significant proportion of the country's generated power, so the waste will also be significant.

As I've said umpteen times, poor/slow energy transfer does not, per se, mean that there is necessarily a lot of energy 'wastage'.

" I'm out ".

 

[Harry Bloomfield]

As I've said umpteen times, poor/slow energy transfer does not, per se, mean that there is necessarily a lot of energy 'wastage'.

" I'm out ".

As simply as I can possibly put it....

If the input to the charger is 100Kw, and only 50Kw is making it into the battery, that is a loss of efficiency of 50%. What the actual wireless loss might prove to be, I don't know, but it will certainly be much higher than can possibly be achieved, via wired.

Why do you suppose, old-fashioned, copper wound transformers are so carefully designed to minimise losses, and have a core linking the input and output windings?

 

[JohnW2]

As simply as I can possibly put it.... If the input to the charger is 100Kw, and only 50Kw is making it into the battery, that is a loss of efficiency of 50%.

Indeed it would be .... but, if that were the situation where are you suggesting that the other 50% might be going, and being dissipated?

If you would like a slightly easier version of that question, consider a hypothetical situation in which, other than for the intended 'receiver coil' the nearest other conductive material was a mile away from the 'sending' coil. Do you still think it would be possible for 50kW of power to "get into, and be dissipated in, something"? If so, what and how?

Why do you suppose, old-fashioned, copper wound transformers are so carefully designed to minimise losses, and have a core linking the input and output windings?

To increase the coupling between primary and secondary, thereby increasing what I've been calling 'effectiveness' (of energy transformer). Again, if you think that there would be lots of 'losses' (poor efficiency) in the absence of a core, where do you think that the 'lost energy' would then be dissipated?