Menu

Power Calculations

I’m doing the final tweaks and tests with the weather station. Weather in Oregon has been really crappy and I have the solar panel in a mostly shaded location (worst case scenario). To date, the system has been pretty reliable.

I’ve been doing some power calculations and I think we are going to be OK with the 100w panel and 20Ah battery.

Power Consumption Calculations:
Micro Router: 112mA (avg)
USB Modem: 165mA (avg)
Wx Display: 200mA (avg)
Wifi Camera: 550mA (avg)
Total of 1027mA (avg)
 
Amps x Voltage x 24 hours =
1.03A x 5V x 24 = 123.6Wh per day
 
Solar Power Requirements:
Rated panel wattage = 100W
Solar hours (for Portland area) = 3.5 hrs per day
Efficiency loss = 40%
 
Average Wh per day calc:
Panel wattage x avg solar hours x loss = daily Wh
100W x 4h x .4 = 160 Wh
On a cloudy day:
100W x 2h x .4 = 80 Wh
 
Charging in a day
80 to 160 Wh
80 x (1000/12) = 6666.7 mAh
160 x (1000/12) = 13333.3 mAh
Battery Charging
20 Ah battery capacity
 
Equipment Consumption in mAh
Wh x (1000/5v) = mAh
123.6 x 200 = 24720 mAh per day
 
12v Battery has 20000mah capacity 
2 days to fully charge from completely dead
 
I guess a big concern is how long it will the 12V battery last. Will it last a year? Two? At $40, it isn’t a horribly expensive item to replace each year. I need to do further research on how to measure/evaluate battery health…