heres no info. on the site and no talk about lithium on the site - how would that even work - balance etc,
rickystyx wrote:It looks like it is just a basic electrical transformer with one coil mounted on the chair and the other half on the stand - Transformers are very efficient so nothing really clever in it and you would have to ensure it lined up carefully or lose all of that efficiency - not that much better than connecting a plug really
c500user wrote:rickystyx wrote:It looks like it is just a basic electrical transformer with one coil mounted on the chair and the other half on the stand - Transformers are very efficient so nothing really clever in it and you would have to ensure it lined up carefully or lose all of that efficiency - not that much better than connecting a plug really
It is not quite as simple as you suggest. If you were to connect one coil of a transformer to your charger and the other to your chair make sure you move away very quickly. Be prepared for sparks and possibly fire because you would fry the transformer!
Transformers are AC only. They cannot be used for DC.
Burgerman wrote:Part of the issue is that a transformer gets its efficiency from its laminated iron core. And with wireless charging there is no continuous iron core. So high frequences are used to get it to transfer its power more efficiently. But it needs a lot of area, and the closer the better.
Its OK to charge a proper powerchair with 70Ah batts with 8A as long as you have 8 or 10 hours or more.
Its not OK to charge a 200Ah lithium battery at 8A though because that would take a rather long time! Which is why the 40A PL8 charger is better. Even at 40A, you need 5 solid hours and a bit as CV declines.
So that gadget would need to be much, much bigger! And its already too big.
Burgerman wrote:Since its large and complicated, and guides itself in, and positions itself correctly, wouldnt it just make more sense to have metal contacts... Like my auto mower, kettle base, etc.
They are just adding this wireless part for no sensible reason. Then it could charge faster. And with higher efficiency and 'save the planet'...
ex-Gooserider wrote:In the US kettles seem to use wireless connections, ditto electric toothbrushes and lots of other small electronics (but our phones still have to plug in... )
However they are using very close coupling in that you have a charger base that the device drops onto so basically just the two layers of plastic housing is all that separates the inductors...
This has the advantage of totally isolating the shocking bits from the user, and also means that there is no concern about water / dirt / corrosion, etc. on metal contacts... OTOH I could see the same sort of 'docking arm' arrangement being used w/ an XLR plug or other low-insertion force connector, assuming there was good enough guidance for the arm to find the right hole... As always, its a question of picking the trade-offs....
ex-GooseriderBurgerman wrote:Since its large and complicated, and guides itself in, and positions itself correctly, wouldnt it just make more sense to have metal contacts... Like my auto mower, kettle base, etc.
They are just adding this wireless part for no sensible reason. Then it could charge faster. And with higher efficiency and 'save the planet'...
Since its large and complicated, and guides itself in, and positions itself correctly, wouldnt it just make more sense to have metal contacts... Like my auto mower, kettle base, etc.
Irving wrote:c500user wrote:rickystyx wrote:It looks like it is just a basic electrical transformer with one coil mounted on the chair and the other half on the stand - Transformers are very efficient so nothing really clever in it and you would have to ensure it lined up carefully or lose all of that efficiency - not that much better than connecting a plug really
It is not quite as simple as you suggest. If you were to connect one coil of a transformer to your charger and the other to your chair make sure you move away very quickly. Be prepared for sparks and possibly fire because you would fry the transformer!
Transformers are AC only. They cannot be used for DC.
I don't think Ricky was advocating connecting DC to a transformer. He is indeed correct about the efficiency of transformers and that wireless charging is effectively a transformer. However, wireless charging uses much higher frequencies than a conventional mains transformer, which is a magnetic device, and is more akin to radio transmission and as such is a very lossy process. I've recently been working on remotely charging/powering medical implants from outside the body using wireless techniques and even at those short distances & low powers losses can be 30% or more!
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