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Discussion Starter · #1 ·
I have a crazy Idea, if it has already been mentioned in another thread feel free to delete this one.

In a 3 Phase System:
Could you Disconnect the Wires from the Controller to the motor and then feed Grid 3Phase 50/60hz ~415/450VAC into the same wires?
The Controller would think it was getting regen from the motor and in-turn feed the power back into the batteries.

This would eliminate the need for a separate battery charging system that would be fairly costly.

You would need to regulate the power input from the 3Phase Mains "regen amount" You could build a very basic power regulator that communicated with the BMS and when the BMS started limiting the power into the batteries you could slow or stop the mains power from going in.

Crazy? Doable? or Done already?
 

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The controller frequency would have to be synchronized with the grid frequency. Like a grid tie inverter.

A phase angle controller made using SCRs would work much better, or even regular rectifier diodes.
 

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Discussion Starter · #3 ·
The controller frequency would have to be synchronized with the grid frequency. Like a grid tie inverter.

A phase angle controller made using SCRs would work much better, or even regular rectifier diodes.
speed=(120 x freq)/no. of poles
I just figured a 50Hz signal would "trick" the controller into thinking the 4-pole motor was spinning at:
1500=(120 x 50)/4

I thought it had to be more complicated else more people would be doing it :p
 

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Well yes you can match the frequency of the grid with the controller (after acceleration) , but that doesn't mean you'll match the phase. The controller might be going negative(negative half sine) when the grid is going positive (positive half sine)

And again, SCRs or regular diodes don't care about the phase.
 

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Could you Disconnect the Wires from the Controller to the motor and then feed Grid 3Phase 50/60hz ~415/450VAC into the same wires?
The Controller would think it was getting regen from the motor and in-turn feed the power back into the batteries.

Crazy? Doable? or Done already?
Doable, and has been done by AC Propulsion:

http://www.acpropulsion.com/products-reductive.html

I believe that the Tesla Roadster does this also, and at least at one stage licensed technology from AC Propulsion. So there may be patent issues with implementing this certain ways.

The other issue is that you have to either use the inductance of the motor, or add external inductors. You also need appropriate software, and since this system is capable of bidirectional power transfer (battery to mains as well as mains to battery), needs regulatory approval, which is costly. The external inductors add weight and take up space, and are more expensive than a cheap, low power charger. If you use the motor's inductance, you have the issue of the possibility of the motor's shaft moving, and safety issues. You also need extra contactors to switch the mains in and either the motor out, or the motor in series with the mains.

All these extra inductors, contactors, software and regulatory approval makes the idea unsuitable for replacing an overnight charger. However, it allows fast bidirectional charging (V2G, Vehicle to Grid), which would otherwise be more expensive and add more weight and take up more space in the vehicle.

So in summary: good if you want a fast charger and/or V2G, bad if you want to save $700 to a few thousand dollars on a 2-3 kW charger.
 

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Discussion Starter · #6 ·
So in summary: good if you want a fast charger and/or V2G, bad if you want to save $700 to a few thousand dollars on a 2-3 kW charger.
Cool! Yea I didn't realize it was so complicated. It would be nice to couple this with a Solar System and use the vehicle for V2G in your house at night or to balance/supplement the power generated from the solar.
Only problem is you'd have to do all your driving in the evening after charging during the day. Or supplement with Wind power. This means there is no "Grid Connect".

I think a traditional charging system will have to suffice for now :)

V2G seems like a really cool idea tho, if there were 10,000 vehicles parked at their workplaces with V2G smoothing out the Grid it would give heaps more options on how to mange power generation.

They are putting Smart meters in Australia at the moment that give 30min readings and allow granular demand management.
 

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Grid tie or battery back up to your solar will work great. Charge battery bank during the day and charge from them at night. Or if your grid tied it makes no difference when you charge. Using the controller as a charger you must also be able to stop the charge at the proper voltages and amps. It is not a simple thing to do.
 
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