Disaster Solar

This is one of my first setups! It’s a 30W Solar Panel, 22 Amp Hour Battery, and a cheap charge controller.

$84.50+$45.15+$19.99= $149.64. 

Since these components are all low voltage DC, and the amperage put out by the solar panel is quite low, I suggest you use standard 2.1×5.5mm DC barrel plugs to connect everything. Grab a pack of 10 male  and 10 female from Amazon. If you keep developing solar power setups as a hobby, you’ll definitely use them all eventually, and a pack of 10 barrel plugs is roughly the cost of 1 ‘solar panel connector’ like this MC4. These also have the benefit of connecting directly to devices that use 2.1×5.5mm barrel plugs, though you should always take care to ensure you provide the voltage your device expects, and that your battery and voltage regulators are capable of providing enough current to power your device.

The Wi-Fi radio in this system is a Ubiquiti Nanostation Loco M2. It’s running the Commotion DR2 firmware, which allows it to broadcast an Access Point locally while simultaneously communicating with a distant radio.

In order to maintain portability, I went with a 22Ah battery, which weighs only 14 pounds (6.35kg). I wanted a system that could be put in a backpack or travel box, and still be comfortable to carry with 1 hand. This system is pretty powerful considering its portability, but is still a little undersized for Ubiquiti devices. I’ve used a 5W average power consumption for the calculations below.

Based on my power measurements, this is actually a slightly too small panel and battery to run this load 24/7. The M2 Loco draws between 4 and 8 Watts when being used. The Nanostation can drain a 22Ah 12V battery in 33 hours-53 hours, depending on the number of users. So this system works great for occasional or temporary use… i.e. 16 hours a day, or for up to 2 days in an emergency. I try to run it for 20 hours or less at a time, to ensure the battery never drops below 50% charge.  With a 50W solar panel and a 40Ah battery, you could run a Nanostation M2 Loco 24/7 even with 2 days in a row of no sun.

 if you want to run any device off solar power 24/7/365, step 1 is to determine the ‘minimum hours of sun per day in winter’ using a U. Oregon sun chart. You also need to determine the average and/or maximum power consumption of your device, and determine either how many days in a row without sun your area can get, or if the occasional failure is acceptable, the number of ‘reserve days’ you can be powered with no sun.

If you want to perform the calculation above for your own devices, I made a spreadsheet that does the math for you. You’ll also find power measurements from common devices, including the Nanostation M2, TP-Link 703N, Raspberry Pi Model B, and some newer devices, such as the Village Telco Catbert and Koruza Wireless Optical Device.