Solar power... AC/DC

Hi all,

Just musing here. I am looking at installing some solar collectors on my roof. Then a thought hit me. My house runs on AC current. My EVSE sends that AC power to my car and it converts it to DC current to be stored in the battery. The premise of the DC Quick Chargers is that they do the conversion and delivery a bunch of DC to the battery and bypass the onboard converter. So, back to solar. My solar panels would produce DC power. I would then convert it to AC and use that in my home. Some of which might be used to charge my FFE. DC to AC and back to DC. Is there any possibility of a device that would take the DC directly from the solar and deliver it directly to the car battery? Maybe even bypass the onboard unit.

I'm sure smart people have already considered this, and since I don't see anything written about it, have dismissed it as impractical.

Any thoughts?

Marv

Although I'm an EE, I'm not a power expert; but I'll give you my thought. One of the reasons we have AC as a power distribution system in the US and most parts of the world is because it can be transformed to whatever voltage you want. Those high voltage wires overhead can be reduced to 120 through a few different AC transformers. With that said, the voltage to charge your car has to be controlled keep your Li batteries happy. The voltage from your Solar array will not be that voltage and must be transformed to what the car wants to see. To do that, you would need to convert your DC solar voltage to AC so it can be converted to a different DC voltage that is appropriate for the a vehicle charging circuit. The intermediate AC voltage wouldn't necessarily need to be 60HZ 120V or 240V, but it will be alternating at some frequencies.

But you are likely correct that you need to get rid of the middle men. There is an inefficiency loss going through the solar inverter to the grid, and then coming back out of the grid to your car that has inefficiencies converting that AC to DC. If there were just a single conversion from Solar DC to vehicle DC (although a conversion process would be needed that would would have loss associated) you would be better off.

Thanks for the reply. Appreciate your thoughts.

The problem would be:
-The DC voltage is different between systems. The DC to DC converter would have to have a wide input range.
-The DC current to the car would have to be variable...it will change throughout the day and if a cloud passes over.
-The system would still need an AC inverter to take the excess charge and put it in the grid.
-If you change (or can change) your billing to Time of Use (TOU), you may get more credit from your power company for your solar energy than what it will cost you at night to charge your car. For instance, my solar array generates about 30 cents credit per kWh, but costs my only 10 cents per kWh at midnight. So directly charging my car during the day wouldn't be good for me....although Southern California Edison is changing the rules to be less beneficial to me.