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Solar Switching - Have an idea? Answered

Hi All, I have an PV grid system newly installed, now I have looked at how to store the excess power but want a cheap controller to switch on the battery charger when I export, now there is gadgets with clamp meters but the can range from £180 to £300 quid which isn't cost return effective in my opinion, anyway being new to the PV world I'm currently monitoring my system and noticed every time I export my electricity meter has a solid red LED light up, this makes me wonder could a simple LDR circuit be made to after say 5 seconds of a solid output of the LED switch on a relay which in turn controls a battery charger, I want the delay in switching cause when I'm using the grid it blinks and don't want it switching on and off at that point, Hope someone can help, Many Thanks in advance, Matt

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steveastrouk

Best Answer 4 years ago

Sounds like you could use an LDR to do it, with a timer. You can probably do it with one of these

http://www.ebay.com/itm/Autonics-AT8N-Multi-Functi...

...in power on delay mode - the output goes high after the timing period elapses, and if the trigger resets, the output stays low.

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Matth354

3 years ago

Thanks Guy

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Matth354

4 years ago

Hi Nick,

Thanks for this, I did look at immersun and iboost but have a combi boiler fitted with little room to convert back to a tank,

Batteries are no problem as I have a family member who owns a company which services fork lift trucks, so 2v cells are easy to get and no cost will be involved saving a huge amount on my part,

I also have my sparky brother for the mains switching gear and inverter installation at trade prices, he suggests installing a light sensor to switch the grid off and move to battery using a monitor he can get the grid back when the battery drops low,

Auditing our usage I work 9-5 my wife works nights so during the day she's asleep and the kids are at school so must of what we generate even with careful planning is exported,

Most of our usage is from 5pm - 10pm when the sun is low or none in winter,

From 10pm till sun up also uses around 1.8kw which could be supplied by battery too.

Cheers for the reply

Matt

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rickharrisMatth354

Answer 4 years ago

I have no idea where they get them but the sensor for my Iboost is tiny and I guess cheap. It is working off the AC input cable - possibly it senses when the voltage falls to zero - ie when the panels are producing as much current as the incoming supply is providing. As you say a red LED comes on on the meter and mine reads rev Volts.

You could try as Steve suggests a simple LED taped over the LED to turn your supply over to your battery charging cct.

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Matth354

4 years ago

sorry Rick :-)

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rickharris

4 years ago

Storing the energy in a battery bank is actually quite costly. the batteries need to be stored properly, regularly maintained and you need quite a lot of them to be useful, either in terms of voltage or current storage. You also need to feed back into the inverter your PV system uses or a separate inverter unless your going to wire a DC based electricity system through the house. Feeding back to the PV inverter would be quite complex.

What my Solar panels do is I have a solar boost system installed. It measure the current flow in the mains cable - If it is going out of the house, i.e. we are not using the electricity generated then if the hot water tank is below temp it diverts the electricity into the immersion heater to heat up the water.

When the water is hot it sends the electricity back out to the grid. Thus I am storing the energy in a useful form that is already there and needs little maintenance. It isn't quite using all the generated energy but it reduces my need to heat water with gas or electricity.

My system has been in almost a year now and works great. 4KW of panels have so far given use about £1000 back in FIt payments and a very significant saving in electricity usage and gas usage over last year - about 2/3 of gas has been used and about half the electricity.

Your PV cell installer would be the best guide as to what you can do to store the electricity if you really decide to go that way.