A couple of our tree houses do not have electricity due to their more remote locations on the property. In an attempt to bring some illumination into those areas to demonstrate as well as embrace the options of solar energy, we have developed a simple and effective source of power.
We located a suitable a 10 foot long, 12 volt LED rope light. This only consumed 4 watts of power (under 0.4 of an amp). Given that we wanted the battery to support at least 20 hours of usage, it calculated out to requiring about a 7 Ah battery.
We then constructed a small battery box, that contains a 12V Werker SLA (Sealed Lead Acid Battery) 8Ah SLA Battery. These batteries are light and safe, require no maintenance and are completely sealed. The battery box required a cigarette lighter socket to plug the LED rope light into, and another polarized connector to connect it to the solar panel, while it was being charged. After searching some options, we finally settled on a 12 volt auto trailer light connector. Simple and very inexpensive. , We also employed a small voltage controller. Morningstar manufactures a couple of useful ones for this project. The voltage controller has two main functions: it simply makes certain that however long the battery is left on charge, it will not overcharge. it also makes sure that when the battery starts to run down it turns off the lights instead of completely discharging the battery. This is called LVD or Low Voltage Disconnect. A charge controller is a must, otherwise you will very quickly damage the battery and severely impact its lifespan.
The charge controller lives in the battery box and shows the status of the battery: low, medium or fully charged. The LVD light also indicates if the voltage has become too low to operate the lights. We then installed a 20 watt solar panel on an old satellite dish support and obtained an optimal location for both winter and summer sun. The batteries easily provide lighting for three nights before requiring a recharge and the battery box recharges in about 5-7 hours. A fuse was added simply as a precaution in the event that the lights were ever damaged and caused a short.
We love the idea of making people aware of how are resources are not infinite. Being handed your “electricity-in-a-box” does make us a little more inclined to conserve and be a little more frugal with its use.
Here is a list of the parts required to do this yourself. We show all the parts being obtained from Amazon, but clearly there may be more local and possibly cheaper sources for what you would need.