Need switching device controlled by insolation. Does it exist?

[DanS26]

I'd like to control a 40 to 70 amp AC switch to recharge an electric powered automobile. My goal is that my PV array will provide the power. Thus the switch will only close (ie switch on) when insolation and time of day is optimum. What I envision is a device that can measure light intensity, then electronically 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. I know I could use an heavy duty timer to say turn on at 10am and shut down at say 5pm, but my goal is not to use any utility power for my EV, so that on cloudy days the switch stays open.

Could a switch like this be built from off the shelf parts?

[Sunking]

You are going about this all wrong. You do not want to use the PV to just charge your car. You would be screwing yourself out of quite a bit of money. What you need is a grid tied PV system so every little drop of electricity generated by the PV system is utilized and put to work.

[russ]

Does your state have net metering? Where you can export power to the grid and either get paid for it or get credit for later use?

To charge a car with a stand alone system I believe you would have to have a large battery bank - with grid connect the utility provides the equivalent of a super size battery bank.

The part you are talking about building? Don't for many, many reasons. The fact you are asking says you are not an electrical/electronics expert. That can get messy such as in burning the place down!

Russ

[DanS26]

You are going about this all wrong. You do not want to use the PV to just charge your car. You would be screwing yourself out of quite a bit of money. What you need is a grid tied PV system so every little drop of electricity generated by the PV system is utilized and put to work.

I currently have an 8.5kw system that powers my house. It is a grid tied system so that I have excess power to use during daylight hours. Again my goal is to use this excess power to recharge an EV. I would tie the switch into the current house wiring not to a dedicated inverter. And that's my problem, how to control the switch so that is only closed (ie recharging the EV) during excess sunlight producing hours.

My utility uses net billing so that it is even more incentive to use excess power for internal use.

Dan

[DanS26]

Does your state have net metering? Where you can export power to the grid and either get paid for it or get credit for later use?

To charge a car with a stand alone system I believe you would have to have a large battery bank - with grid connect the utility provides the equivalent of a super size battery bank.

The part you are talking about building? Don't for many, many reasons. The fact you are asking says you are not an electrical/electronics expert. That can get messy such as in burning the place down!

Russ

Hi Russ,

I designed, assembled and installed, all by my lonesome, an 8kw grid tied system. I have all the necessary expertise, contracts, permits, etc. Please don't make assumptions about my qualifications.

Now, I live in Indiana and receive power from an REMC, which is a member owned, non-regulated utility. My contract is for net billing. Thus my inquiry about a switchable AC disconnect device dedicated to using excess power generation to recharge an EV during daylight hours will make sense to you. Thanks for your reply though. I just thought the brain trust at SolarPanelTalk may know of the device I'm looking for or at least offer advice on how to build it.

Dan

[russ]

Installing factory bought equipment (somewhat like Lego land) is a bit different than designing a car charging system - that is what I meant - if you don't understand what you are getting in to then you certainly should not be going there.

Sunking would not be doing what you are talking about.

[DanS26]

Installing factory bought equipment (somewhat like Lego land) is a bit different than designing a car charging system - that is what I meant - if you don't understand what you are getting in to then you certainly should not be going there.

Sunking would not be doing what you are talking about.

Thanks again for the reply. What I hear you saying is that these devices do not exist or that you are not aware of these types of devices.

Dan

[Sunking]

No Dan it dies not exist nor do you need any such device. You cannot control where the power is going in a grid tied system. They must be connected to the grid in order to operate as they are operate that way.

But take this FWIW, if it were possible, you would be screwing yourself out of money.

[Ian S]

I'd like to control a 40 to 70 amp AC switch to recharge an electric powered automobile. My goal is that my PV array will provide the power. Thus the switch will only close (ie switch on) when insolation and time of day is optimum. What I envision is a device that can measure light intensity, then electronically 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. I know I could use an heavy duty timer to say turn on at 10am and shut down at say 5pm, but my goal is not to use any utility power for my EV, so that on cloudy days the switch stays open.

Could a switch like this be built from off the shelf parts?

I'd be interested to know why you want to do this. With your grid tie system and net metering, your PV production is kind of fungible going into the grid when in excess and coming out when not. I don't know about you but I'd still like to have my EV charged even on cloudy days.

[Ian S]

No Dan it dies not exist nor do you need any such device. You cannot control where the power is going in a grid tied system.

As I understand it, all he wants to do is to charge his EV when the sun is shining and not have it charge when it's dark or cloudy. All he's after is an automated method of plugging in his EV when the sun is shining and unplugging it when it's dark or cloudy. Maybe some kind of light controlled circuit that switches a high current SSR. Can that even be done to code?

[DanS26]

As I understand it, all he wants to do is to charge his EV when the sun is shining and not have it charge when it's dark or cloudy. All he's after is an automated method of plugging in his EV when the sun is shining and unplugging it when it's dark or cloudy. Maybe some kind of light controlled circuit that switches a high current SSR. Can that even be done to code?

Exactly, and the reason I want to do this is that my utility buys back my excess power at a wholesale rate not the retail rate. Thus it is better for me to use my excess power to recharge my EV than to sell back to utility. I use my EV around town, not long trips, thus I have plenty of excess power stored in the EV batteries to go without charging for many cloudy days. Yes, if its cloudy for a week or more I might have to manually override the switch and charge from the grid, but I want to avoid that.

Think of it this way, I have a motion detector that turns on my outdoor security lights. An electronic switch is activated by motion. I'm looking for a device activated by light. Look at the devices turning on and off the mercury vapor lamps on all the major highways. Mega-amps there. Same difference.

[Ian S]

Exactly, and the reason I want to do this is that my utility buys back my excess power at a wholesale rate not the retail rate. Thus it is better for me to use my excess power to recharge my EV than to sell back to utility. I use my EV around town, not long trips, thus I have plenty of excess power stored in the EV batteries to go without charging for many cloudy days. Yes, if its cloudy for a week or more I might have to manually override the switch and charge from the grid, but I want to avoid that.

Doesn't your utility net out usage first before paying for any excess generated (payout at the end of some time period like a year?) If so, then I fail to see how your plan would save any money.

[DanS26]

As I understand it, all he wants to do is to charge his EV when the sun is shining and not have it charge when it's dark or cloudy. All he's after is an automated method of plugging in his EV when the sun is shining and unplugging it when it's dark or cloudy. Maybe some kind of light controlled circuit that switches a high current SSR. Can that even be done to code?

Ian,

Are you familiar with transfer switches for stand alone generators? They use a low voltage signal to trip high powered magnets to switch power supply. That type of device is pretty close to what I have in mind. But instead of switching power sources, it would just act as a 50 to 70 amp on/off switch.

Dan

[DanS26]

Doesn't your utility net out usage first before paying for any excess generated (payout at the end of some time period like a year?) If so, then I fail to see how your plan would save any money.

This is Indiana and they do things differently. I buy power from them at retail and sell them my excess at wholesale rates. Two separate lines on the monthly bill.

[Ian S]

This is Indiana and they do things differently. I buy power from them at retail and sell them my excess at wholesale rates. Two separate lines on the monthly bill.

OK that makes sense then and is different from how my utility here in Phoenix works. Hope they don't switch to your plan! Anyway, I'm not really familiar with transfer switches but it sounds like a potential option.