Pretty slick to split the on board charger into two pieces. Still, I don't see the advantage over direct connection. Our thought was that if one is going to go to all this effort why not just make a probe/port connector mechanism (
). This would also allow for manually driven or autonomous connectivity. Also, with this split charger inductive means, you still need to have a way to charge it from a straight grid connection. So double the circuitry (or 1.5 times?)
But either way, or some other way, needs to become a standard for it to do much good.
That is really good work. Thanks for posting. And I think each of the perspectives have a lot of merit.
Here are some adjustments in reverse order
n) Yeah, there needs to be a standard, or defacto standard. Tesla, or Toyota, or some China based manufacturer could make a defacto standard exist. My experience with standards bodies is that there are people who are participating that are paid to serve the interests of their employers. Defacto standards work better. This approach is about safety and efficiency. I am not sure the luxury market cares enough about efficiency for this.
n-1) There is actually very little of the split circuit that ends up in the car. About 1/4 of the losses (1% of total power delivered, as we expect 96% efficiency) with no active switching devices - just diodes, capacitors and feedback. It is about 1/6th of the circuit that is in the car by PCB area.
Let's look at the part that goes in the diffuser of the car. That is an 8 inch caliper for reference. The alignment is planar on the sloped surface to accommodate suspension travel and asymmetries. Using the slope of the diffuser accommodates a lot of suspension ambiguity.
This next picture shows two Litz wire secondary windings, one shown with the oversized return ferrite core that helps control magnetic fields. These two power trains could be interleaved to provide more than enough capacity for home charging for daily commutes. ~7-10 kW.
One would provide 3.6 kW.
The circuitry to smooth the sinusoidal waveform is smaller than a human hand.
This next picture is for completeness (looking up from the pavement). The flash shows where the primary windings and ferrite center leg goes. This active area is 2 inches wider than it has to be.
I think there is enough window to manually park with a back up camera with some on screen sighting assist.
n-2) Yes, there needs to be a conventional onboard charger. Here are some, slightly convoluted, thoughts on that... If super charging and close coupled inductive charging at home are the primary mechanisms for charging, the onboard charger may become vestigial. In the interim, yes.
n-3) The advantages over direct connection are:
a) This is designed for multiuser parking spots. Although it can be implemented in a dedicated spot as a docking post, the objective is flat (< 2.5 inches tall) or subsurface in non-controlled environments. It can be driven over by an F-250 with no damage. It is salt and ammonia impervious. Flooding is not a problem and the target service interval is 10 years. The goal would be that a city or condominium could install this without objection, or service, or vandalism for a long time.
c) Perception of safety. Think about how electric toothbrushes are charged. Do you want a direct connection right beside the sink? There are also benefits of not hooking some utility grounds to the frame of the vehicle during lightning storms.
The goal is inductive charging benefits, with much better efficiency (half the carbon footprint of the latest technology), much lower "on vehicle" weight, and much lower costs (the baseline power supply we are splitting 5/6ths to 1/6th sells for $300).
The close coupling does not have the luxury feel, so you really have to care about efficiency and (perception of) safety to implement something like this.
Note: my employer does consider this as IP, so I have to say patent pending.
