ElectricMotorcycleForum.com
General Category => Electric Motorcycle News => Topic started by: enaef on December 31, 2019, 02:52:39 AM
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https://www.bennetts.co.uk/bikesocial/news-and-views/news/2019/december/bmw-electric-bike-wireless-charging
ZeroMark has asked for something like this five years ago:
https://www.electricmotorcycleforum.com/boards/index.php?topic=6314.msg48647#msg48647
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I can think of some really basic critiques that suggest that this fun and clever patent will never see production:
- Aiming to park so that the kickstand lands squarely in the center of a mat every day seems tiresome. Plugging in a cord that you can leave coiled up somewhere in your garage seems easier. (for outdoor stations, the effort seems quite similar)
- The conductors which might fit in a sidestand are not going to admit much current, so it's limited to trickle/slow charging.
- Inducing a current in the kickstand seems like it might accelerate fatigue in this structural component. It could detract from longevity.
- Fault tolerance and servicing seems harder to manage than for an electrical plug inlet.
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Maybe your bike will be able to be recharged from a traffic sensing loop while you are waiting for a traffic signal to change. ;)
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According to this....
https://www.google.com/search?q=inductance+wireless+charging+efficiency&ie=UTF-8&oe=UTF-8&hl=en-us&client=safari
wireless charging is currently (pun) only 75-80% efficient so I don't see this as a viable solution.
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The current probably doesn't go through the kickstand, Brian.
I always park in the same spot, so I'm tempted to put a stand on the wall there ^-^
-Crissa
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Electromagnetic induction meets only reluctance. The kickstand isn’t magically protected even if it’s isolated electrically.
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I'm with Brian. Someone had a "good idea" that's never going to work very well in practice. Not only would you have to have massive wires running through the kickstand, you'd have to have a ludicrously large bottom pad on the kickstand to get any kind of an efficient coil in there. The kickstand would look like a piece of a baseball bat with a concrete paver stuck on the end. And come on now, how difficult is it to plug in? We've been "plugging in" our ICE vehicles forever when they need refueling.
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Not only sounds very flaky to me, it is also a solution to a problem that doesn't exist, IMO.
-Don- Turlock, CA (RV-- almost home)
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Without being an engineer I also had my doubts if such a wireless charging 'solution' really was an answer to a non-existent problem, as DonTom has put it.
Then a heretical thought crossed my mind and I asked myself if it was possible that a company would go for a patent only to confuse competitors :o ?
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The size of coil is directly related to the range, not the current.
And the diagram doesn't show the moving parts of the kickstand being part of the conductor, it shows a wire there.
You could also use the shape of the kickstand to be part of the loop. But the loop itself never contains the entire current at any single point until the far end where it comes out.
-Crissa
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The size of coil is directly related to the range, not the current.
You're oversimplifying. Think about it. The full induced current has to be supported by the wire in the pickup coil as well as the wires leading from the coil to the charging circuitry (the current is identically the same throughout the whole loop). To achieve any sort of charging power, that current has to be massive. You can't use tiny magnet wire. You have to use some giant wires.
To achieve any sort of coupling efficiency between the coils, you have to use lots of turns of that high-current wire, as well as a good iron or ferrite core on both sides.
The wireless cell phone charging people struggle to pass 5 watts of charging through an area if a few square inches. Scale that up by a thousand.
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Only the cord leaving the coil needs to support the entire current. The receiving coil holds only a fraction of it. This is how inductance works; it's spread over a wide surface.
So it would be like having one of our cables strapped to the kickstand and a disk capacitor there. It wouldn't be any bigger than a soda can or probably the '13-'19 Zero kickstand.
I'm a little surprised this isn't considered an obvious use of a prior patent, tho.
-Crissa
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Not only sounds very flaky to me, it is also a solution to a problem that doesn't exist, IMO.
-Don- Turlock, CA (RV-- almost home)
IMO, that's it in a nutshell. I used to work for a VC, and maybe 80% of the entrepreneurs we met had ideas that failed that basic point. Now, sometimes a solution is developed for a need people didn't know they had (text messaging), but that's fairly rare.
There's no reason to think that this is a problem.
Incidentally, I think wireless charging for BEV cars is mostly a similar issue; it requires a lot of standardization to work.
There are niche applications where people might not be handling the charging cables themselves (very heavy cables to charge ferries, for example, are used in Scandinavia), but in those a robotic charger works well.
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A problem that doesn't exist for us is not the same as a problem that exists for the vast majority who don't yet use what we do.
-Crissa
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Only the cord leaving the coil needs to support the entire current. The receiving coil holds only a fraction of it. This is how inductance works; it's spread over a wide surface.
No, that's just completely wrong. It's a very well-known principle in Electronics that the current in any closed loop (only two nodes, one at each end) is identical at every point in that loop. Current is nothing but the flow of electrons, and electrons can neither be created or destroyed. It's like a closed loop of road with cars circulating around it -- unless you're somehow adding or subtracting cars, the average "car flux" is equal at every single point around the loop. They have to come from somewhere, and they have to go somewhere, just like electrons. Look up "loop analysis" if you'd like to learn more.
Mutual inductance uses a magnetic coupling between two coils of wire to create a voltage on the secondary coil proportional to the voltage on the primary coil, but all that does is push electrons around the secondary coil. There's no magic electron creation or destruction going on, and loop analysis principles still apply. Kirkhoff's laws state that the sum of the voltage drops around any loop is always exactly zero, and the sum of the currents into/out of any node is also always equal to zero.
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A problem that doesn't exist for us is not the same as a problem that exists for the vast majority who don't yet use what we do.
-Crissa
It doesn't take more time to plug a car in when arriving home than plugging in a mobile phone to charge.
The vast majority of people already does that, and while wireless charging of phones is a thing, it's not that common; it's not a significant need in residential environments -- mostly a convenience feature in cars, or other locations where multiple people might be charging.
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My electric toothbrush charges by an induction process. I just place it on top of a plastic dish that is plugged into my wall outlet and it recharges in a few hours after a week of use.
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My electric toothbrush charges by an induction process. I just place it on top of a plastic dish that is plugged into my wall outlet and it recharges in a few hours after a week of use.
They all do nowadays; the reason for that AFAIK is that in many regions, AC appliances didn't meet safety requirements for bathroom use. Once a conversion to low-voltage DC was needed anyway, it made sense for the e-toothbrush to be rechargeable so it could be taken on trips without the charger. Over here, many residences (incl. my apartment) don't have electric sockets in bathrooms at all, since they would require special GFCI circuits, waterproof covers on the sockets etc.
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My electric toothbrush charges by an induction process. I just place it on top of a plastic dish that is plugged into my wall outlet and it recharges in a few hours after a week of use.
They all do nowadays; the reason for that AFAIK is that in many regions, AC appliances didn't meet safety requirements for bathroom use. Once a conversion to low-voltage DC was needed anyway, it made sense for the e-toothbrush to be rechargeable so it could be taken on trips without the charger. Over here, many residences (incl. my apartment) don't have electric sockets in bathrooms at all, since they would require special GFCI circuits, waterproof covers on the sockets etc.
My bathroom electric sockets would also have similar devices - if my home wasn't built 50 years ago. ;)
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GFCI's are very easy to add, and are really cheap insurance in areas like bathrooms and kitchens where wet conditions happen frequently. They really could save your life, and IMO there's really no excuse for not retrofitting older buildings.
I'm a bit more skeptical of AFCI's, however. (Arc-fault circuit interrupters). They're required in lots of places now in new construction, but I'm just not convinced retrofitting is really justified.
Are splash shields really required in bathrooms now? How about kitchens? Those things are great outdoors but I've never seen one yet indoors.
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GFCI's are very easy to add, and are really cheap insurance in areas like bathrooms and kitchens where wet conditions happen frequently. They really could save your life, and IMO there's really no excuse for not retrofitting older buildings.
I'm a bit more skeptical of AFCI's, however. (Arc-fault circuit interrupters). They're required in lots of places now in new construction, but I'm just not convinced retrofitting is really justified.
Are splash shields really required in bathrooms now? How about kitchens? Those things are great outdoors but I've never seen one yet indoors.
I'm not in the US :)
And GFCIs are cheap, but when you're in a rented apartment, it's not your call whether to retrofit them.
For new construction, we have mandatory GFCI for the breaker panel as a whole, not individual sockets; GFCI-equipped sockets are pretty rare & expensive, and there are very few code-compliant locations for sockets in bathrooms anyway.
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Doug, that's a closed loop... which is not how coils, capacitors, or parallel circuits work.
-Crissa
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As for the OP this seems like it's just for the 12V battery. Likely meant for their gas bikes. I know some have the battery so covered up and hard to get to it makes hooking up a trickle charger a pain during the winter and just no-ride weeks.
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As for the OP this seems like it's just for the 12V battery. Likely meant for their gas bikes. I know some have the battery so covered up and hard to get to it makes hooking up a trickle charger a pain during the winter and just no-ride weeks.
That seems extremely unlikely. Trickle chargers are low-current, and all you need is a 12V cigarette lighter accessory socket (in BMW's case, a DIN plug (-; ), or SAE plug or similar wired directly to the battery you can connect the trickle charger to -- that's a $15 addition to any ICE bike, and I've added one to most bikes I've owned and even just rented.
The article specifically talks about electric bikes.
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I guess we'll just disagree on this one.
First that inductive charging is very weak and inefficient compared to wired charging. There is just no way that is charging a 10+ kWh battery in less than a week.
It seems like just another bell and whistle for BMW owners. Luxury = lazy.
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The technology can work. Reduce the gap, increase efficiency.
Here's a working product: https://www.pluglesspower.com/gen2-tech-specs/
I can't say I'd ever use it unless it really became a really common standard. But it does exist and does work!
-Crissa
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Sure it works. The technology exists. But that pickup coil is 35 pounds and 33 inches across, for 7.5 kW charging. That's actually better than I thought, given a 4" separation between the primary and secondary coils, and it would get even smaller with closer contact (the end of the kickstand touching the charging pad in the floor).
I still think any reasonable design in the ~6-7 kW range would be very bulky and unmanageable. It might work for overnight ~1-1.5 kW charging system.
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Because it has a transmit distance of four inches, and an off target distance of several inches as well, Doug. The bike example has a distance in a couple mm.
If we could just roll up and get a kilowatt, well, it wouldn't be such an issue. Especially if these were everywhere you parked your bike ^-^
-Crissa