Need switching device controlled by insolation and time of day. Does it exist?

I'd like to control a 40 to 70 amp switch to recharge an electric powered automobile. My goal is that my PV array will provide the power. Thus the switch will only operate when insolation and time of day is optimum. What I envision is a device that can measure the light, then tell the switch to power on when conditions are right. Then power off if not enough PV power is available, thus avoiding using any utility power for recharging purposes. Surely the Greentech Renewables member brain trust knows of such a device.

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I am a retired electronic circuit designer and happen to be designing my first solar system. While looking up information for my project I came across your question and registered so I could offer an answer. I don't know of a commercial product to satisfy your needs. However to design a solution is not very challenging. The solar panels plus a commercial charge controller plus your switch consisting of a low end microprocessor and a few solid state transistors would do the job. A small solar panel would be used to monitor the insolation level. A microprocessor would know the time of day and would learn of insolation level by loading the small solar panel and measuring it's output power. It would then control a few solid state MOS transistors in parallel to switch the current. Cost of electronic parts would be less than $25 and perhaps as low as $8.

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I don't know of anything off the shelf that will do what you want. Timers are readily available but the insolation input is not. We would need to know more about you PV system and your charging system to help you out.
If you have a grid tied net metered PV system then it does not matter when the charger is operating, if you are zeroing out your energy use with the PV system then the charger is using your PV energy even at night.

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dschantz,
From your question, I can infer that:

You are charging a car battery through a DC connected charger
You are also connected to the grid
You have as much as 70A of PV current available

Not sure if these assumptions are correct or not. As Geeze writes, the parts to build just about any system are readily available - what gets tricky is making it safe to run unattended - but a savvy engineer can work that out over time as well.
If you are already on the grid, why not just recharge at night, when power is cheap? If you have extra power during the day, set a stock charge controller to only charge a smallish battery bank durning off-peak morning hours. You can draw on those as a back-up if you don't want to charge the car at night....

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