I'm building an off-grid security system, based on a smartphone as a 24/7 security cam and an arduino nano for several sensors. A pretty interesting build in my opinion, maybe I'll post about it sometime. But I'm struggling trying to calculate the required values for my system. The three things I need to find are:
- Battery capacity
- solar-panel wattage
Information I have:
The smartphone running in camera mode is the main load, the arduino is pretty negligible. I'm using a Samsung Galaxy S4 with a battery of 2600 mAh capacity. I tested it and found that it lasts 3 hours for a full charge. The phone's regular wall-charger is 5v\2A.
I actually tried to run it with an old solar panel system I got from a friend, which uses a 12v 7Ah lead battery and this set of 10W panel and a 3A pwm charge controller. I used a car-usb-charger (to convert from the 12v on the load output pins on the charge controller) and it didn't hold very long, only for half a day or so.
I live in Israel so at the very least 6 good strong sunlight hours a day.
Here is my attempt for some calculations: 2600mAh battery consumed in 3 hours can be rounded up to a 1Ah load (or, since it is in 5v, to a 1Ah*5v=5Wh load), so overall the system consumes 24A daily (or, 120W). Therefore a battery with 30-50Ah capacity is suitable, and a 30W-40W solar panel will do (since 30W*6h = 180Wh daily output). If this is correct, I'm thinking about buying a 30W solar panel, a 10A PWM charge controller (with 5v/3A usb outlet which is really good for my needs) and a 12v 40Ah Deep Cycle Lead Acid Battery.
Am I doing it right? Is this correct? Please share your knowladge.
All the best, Roei.