Our smallest example yet.

Our smallest example yet

A very small project, that is easy to do, and just a nice project for many different situations.

Part list:

  • Solar panel about 25-30Wp (calculations are below).
  • A small enclosure to be mounted on any wall.
  • Small AGM battery.
  • Two fixed and two switched outputs.
  • One 5A fuse.
  • Indicator LED or battery gauge.
  • Two USB outputs.

We call this project, a greenhouse light on solar, but you might enjoy this on a shed, barn, or where ever.

Hanging LED light 12Vdc – 5W
Hanging LED light 12Vdc – 5W

Sometimes al we need is a little light in a remote area on a lot. Now we can put down cables in conduit from the house, but sometimes al we need is a little sun during the day to have light 24/7.

Now with just one PV-panel, a small 18-24Ah battery and 4 different outputs should do the trick. Two outputs are fixed and two are switched for easy install.

LED Flooder + motion sensor – 12Vdc
LED Flooder + motion sensor – 12Vdc

Maybe a nice LED flooder with motion sensor, they are widely available on 12Vdc. No need for a light switch. If you approach the greenhouse or shed, this could go on a fixed 12Vdc output.

Time to get started. 

Every extra possibility or gadget if you like uses power, so we have to make sure, calculations are right or at the least a bit acqurate. Now, I make assumptions, so better update this list to your needs:

  • Two inside lights 2x 5 Watt LED runs for 4 hours on an evening.
  • Outside light 1x 10 Watt LED flooder runs for 1 hour on an evening.
  • The 4th output run 4 hours an evening, and might use upto 15 Watts an hour, if connected, now this could be a small radio or a BT (Blue Tooth) speaker.
  • Battery-gauge (hardly any power).
  • Dual USB-ports (5V/3A).

Simple math: storage need! 

  • 2x 5W x 4h = 40Wh
  • 1x 10W x 1h = 10Wh
  • 15W x 4h = 60Wh

Now we strongly believe in not dis-charging our batteries more than 20 procent (our reason), but since you might not spent every night in the greenhouse, or use every option, we might take it easy on this rule.

We need power storage for 110Wh and will try to store this as approx. 50% capacity, so the battery wouldn’t be drained after one night. All in all we need to store 110Wh x 50% is just 220Wh. This seems much, but dividing this by 12 Volts, means a small 18-24Ah Gel battery.

These AGM cells can be charged anywhere between 1.5 and 3 Amps, so just a 25-30Wp PV-panel is enough.

12Vdc – 18Ah : Approx. 7.13″ x 3.01″ x 6.57″
12Vdc – 18Ah : Approx. 7.13″ x 3.01″ x 6.57″
12Vdc – 24Ah : Approx. 6.5″ x 6.9″ x 5.0″
12Vdc – 24Ah : Approx. 6.5″ x 6.9″ x 5.0″A

On more extra, that hardly uses power is a small batterymeter, we you could check the battery-gauge or just use a 12v signal indicator that is simply on if power is present.

Battery gauge 5-LED's, 12Vdc + on-switch
Battery gauge 5-LED’s, 12Vdc + on-switch

Even where it would be no problem to use our small favorite BSV-20A charge controller, we found something nice and even smaller to fit our smallest project, these miniature controllers are available in a 3 and 10-amp version at only 2.72″ x 2.01″ x 0.89″.

Small controller
Small controller for our small project.
Case with 14 screw-connections for PV-panel, Battery and the four outputs.
Two outputs are switched
Two outputs are switched, connecting to the LED-lights makes that an easy install.


Assembly coming soon

More funstuff:

Looking at the inside of the enclosure it’s only the tiny charge controller in there, that seems like a waste of space. The rest is filled with wiring.

Since this example is design for a shed or garden house we build something extra just for the fun of it.

  • A Bluetooth module.
  • 2x RCA plugs to connect an amplified speaker.
  • A small buck module to feed our BT-module with just 5-Volts.

With this toys that hardly use space or power we can easily connect a cellphone through Bluetooth and stream music to the RCA plugs.

KRC-86B Bluetooth module:

KRC-86B Bluetooth module.
KRC-86B Bluetooth module.

A very small PCB, 1.26″ x 1.26″ with more than enough connections to please. It has the new CSR-chip for better audio. The module is sold with an extra LED an 470uF capacitor. The only connections we use is power-supply, the status LED and the outputs to the RCA-plugs.

Since this module uses only 5-Volts we have another, even smaller PCB, with a DC-DC inverter from 12-5Vdc.

Amplified speakers:

This might sound scary or difficult but every set of computer speakers with a seperate power supply of 12-Volt could be used.

Remote control an output:

Another thing using the extra space in the enclosore could be one remote-controlled output.

Remote controlled output,.
Remote controlled output, typically the 4th one.

Some idea’s are:

  • The outside light on a shed or barn.
  • The bedroom-loft light in a tiny house.
  • Some storage space.

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