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Solar PV for our shed


Mars
 Mars
(@editor)
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I’m looking into how I can hook up a solar panel on our shed roof that can charge a battery that will occasionally be used to power some lights inside the shed.

What will this entail? Is it even worth doing?

Caernarfon 18kW ASHP from Global Energy System – 6.16kW solar PV array
Follow our sustainability journey at My Home Farm
Our heat pump installation: https://youtu.be/c3V0k_GeFOo


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Derek M
(@derek-m)
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Posted by: @editor

I’m looking into how I can hook up a solar panel on our shed roof that can charge a battery that will occasionally be used to power some lights inside the shed.

What will this entail? Is it even worth doing?

I am assuming that you don't have a 240v power supply to your shed.

I suppose that it depends on how many lights and their power requirement and how often and for how long they would need to be powered.

My wife has installed quite a number of fairly high power solar lights in our back garden, the type of which could possibly be used for your purpose at quite reasonable cost.


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robl
 robl
(@robl)
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@Mars

I've done this kind of thing - there's an easy way, and a hard way!

The easy way is to buy a solar panel + battery + PIR light like the one linked below, and put the PIR+light bit inside the shed.  The crucial details are to get one that goes completely off when the PIR doesn't detect anything(some are on dim all the time, bright when PIR detects - they don't like UK winters and end up flat), also that the PV panel is separate to the PIR sensor & led.  I recommend Li-Ion based units.  Nb: I'm not recommending this specific unit, it's just so you know what I mean!

https://www.amazon.co.uk/Powered-Motion-Sensor-Security-Outdoor/dp/B075NLZ92X/ref=sr_1_22?keywords=solar+pir+sensor+light&qid=1655907453&sprefix=solar+PIR+sen%2Caps%2C163&sr=8-22

The more complex way it to buy a panel, and a battery controller, and a battery, and a light, and a switch, and some wire and don't forget a fuse...  It is more flexible... but much more effort, will cost more, and will end up flat 'cos you leave the light on!

 

 


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Mars
 Mars
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Topic starter  

@robl, that’s good out of the box thinking. Simple project to do. Would need the ability for the light to be turned down because won’t need something like a 1500 lumen floodlight in the shed 😀 - love the premise though.

I’ve been looking at a kit that comes with a 12V 1000 amp lithium battery - it’s expensive though. If that was connected to a lamp or strip light I assume I wouldn’t need to have a transformer to drive them. Am I correct?

Caernarfon 18kW ASHP from Global Energy System – 6.16kW solar PV array
Follow our sustainability journey at My Home Farm
Our heat pump installation: https://youtu.be/c3V0k_GeFOo


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robl
 robl
(@robl)
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@editor 

To turn down the light brightness, you'd generally put a resistor in series.  I wouldn't be worried about buying a unit like the one linked, opening it, and putting a 100ohm potentiometer in series, like this one:

https://www.amazon.co.uk/Taiss-RV24YN20S-Carbon-potentiometer-single-turn/dp/B07JMLJJPX/ref=sr_1_18?crid=385BSV2PAA2GG&keywords=100+ohm+potentiometer&qid=1655972818&sprefix=100+ohm+potentiometer%2Caps%2C106&sr=8-18

Use the middle pin on the pot, and one of the end ones, and solder it in series with the lamp.  Then when you turn the knob the brightness will vary.  The resistor will dissipate a little heat, so just pick one big enough - I think the one I linked looks fine.  You could go way more complex to avoid that tiny loss of power, but honestly it isn't worth it!

With the other approach, you're quite right - no need to transform the voltage up and down, best to keep 12V and drive 12v ready leds directly.  You may find a series resistor is a good idea again as your battery under charge is likely to be slightly over 12v, so the leds will run a little brighter.


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