Solar Powered Christmas Light System

I own a business doing commercial Christmas Light installations. I lease equipment to almost all my customers for the required lighting they want, so I use the best equipment as I want the customers to be super happy.

Over the years, I have had needs to provide lighting displays in areas that do not have AC power available. I have used alot of solar-powered mini light sets and commercial-grade battery-powered mini light sets. I have not been happy with the results.

The sets with the little solar panels are not very bright and often don't last thru the entire night before they run down. The battery-powered sets are nice and bright, but I usually have to replace the batteries in the sets at least once during the season. They are also very limited in colors and styles of lights available.

I have thought of building a system with a big battery, solar charger, Invertor and photo-timer to run big bulb (C9) Led light strings. I decided to engineer something more efficient than what I would get with that setup and less expensive to construct. Nothing is available for sale to do what I want without be cost prohibitive.

The LED C9 bulbs I use are mostly SMD technology and Dimmable. They operate at 120v AC at about 0.5 watts per bulbs. Each LED Bulb has a voltage convertor that changes the pulsed AC power to DC power inside the bulb to run the LED SMD elements on DC. If running the sets on pure DC, the voltage only needs to be about 70v DC for the LED to light.

I have built a prototype system using 6 12v 17ah batteries in serial. I have a 12v photocell controller (ON at Dusk, OFF at Dawn) wired to the top battery in the string so it only gets the 12v needed to operate and switches the positive lead. The negative of that battery feeds to the remaining 5 batteries in the string with the last battery providing the negative for the lighting circuit. The lighting circuit has a nominal system voltage of 72v with an actual voltage of 72 - 84 volts.

I needed 86.4 volts from my solar panels to charge the battery string, but didn't want the expense (and space) for 6 solar panels. I got a 1500watt Buck/Boost DC/DC convertor to bump up 2 12v solar panels to a constant voltage I set at 86.4 to charge the batteries.

So far the testing is going great. The batteries are maintaining a good charge after a solid 10 hours of lighting the lights. I have run them 3 days with no solar charging and just had 1 cell drop below 13.0 volts.

Thought I would share for anybody interested. Pics to follow.

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Solar Powered Christmas Light System