DIY fully off grid power for my ham radio shack!

I have been experimenting with various changes to finally achieve fully off grid power supply for my amateur radio shack. Started off by purchasing 180W monocrystalline PERC solar panel with 200W charge controller, 65Ah sealed lead acid battery and 1150VA inverter.

Initially I had mounted the solar panel on a plastic stool on the terrace. My tiny terrace was partially shaded by my water tank on one side and a safety fence on the other sides. Naturally charging was not up to the mark, even though I am in the tropics, at a latitude of about 11 degrees North. Then I decided to raise the solar panel a bit more on a stand used for drying clothes at home. Now it was only slightly lower than the safety fence and charging was better. Still I was not able to get the full potential of the 180W solar panel. While it had taken 3 days for a full charge, now it improved to about one and half days! That seemed quite unsatisfactory for me.

Next step was a bit odd. I took nylon ropes and tied it on the solar panel so that I could lower it over the safety fence on to a lower tiled roof of the sun shade. VU3UQI pointed out that the shadow caused by the nylon ropes on the solar panel could increase the resistance of the photovoltaic cells which are not fully illuminated while the other cells are in bright sunlight. This could cause higher resistance of those cells and eventual burn out of those cells. Being left with no other option at my location, I decided to accept the risk for time being. At a later date, I might try out the alternate option given by VU3UQI of using a frame made of PVC pipes to hold the wires. That can avoid shadows on the photovoltaic cells and risk of cell burn out.

Now that charging of the battery is occurring at a much better rate, I first bought a 55W pedestal fan to run on the inverter. That came dismantled in a box and I had to assemble it with the help of the person who brought it from the vendor! The pedestal fan keeps the shack cool at day time.

One more smaller ‘Pygmy’ fan with light was also bought online from https://amzn.to/4hIhMUX! Please note that if you buy from this link, Amazon will pay me a small amount as an affiliate, at no extra cost to the buyer. Advantage of this one is that it is just 8W and portable. It can be charged from the USB port on the side of the solar charge controller. So it can run without switching on the inverter. Running the inverter has potential for some wastage of energy during conversion from 12V to 220V. This fan runs on a rechargeable lithium ion battery, which is rated as 2400 mAh at 3.7V. As per the specification, the fan can run at full speed for 2 hours or for 4 hours at slow speed. LED indicator shows different colours for different speeds of the fan. There is a different LED for charging indicator on the reverse side which will be blinking red on low battery state and red while charging. Green colour indicates fully charged status.

Yesterday I bought these 10 sq mm insulated copper wires and connector used for inverters from an inverter spare parts shop. They connected the eyelet at one end of the wire and stripped the other end for me. It would have been a bit difficult for me to solder the joint of that thick copper wire.

Connected the eyelets of black and red wires to the 65Ah sealed lead acid battery. Other ends were connected to the three port connector. Battery was also connected to the solar charge controller which was already connected to the solar panel on the sun shade above.

You can see the solar charge controller showing green battery state of charge indication. The blinking ‘sun’ shaped light means that battery charging is going on. When the battery is fully charged it will be lit up continuously instead of blinking. Battery state of charge indicator will become yellow while discharging without charging beyond a certain voltage and later red when it is at low battery state.

Battery voltage is shown as 12.4V on the inverter while the radio is on along with a 55W pedestal fan, both off grid! At fully charged state this can show up to 14.1V.

Positive terminal of the battery connected with wires to the inverter, charge controller and radio.

Left side goes to the radio and right side to the battery, from the connector, which has been taped off as a safety precaution to prevent any inadvertent short circuit. I plan to connect a two way switch here so that I can switch between my SMPS power supply for the radio and the off grid power supply. That will be useful on cloudy days with poor illumination of solar panels.