So I've been reading here for a couple of days in spare time. I'm sure I'm missing pieces here, but examples and getting them corrected is the best way I can learn.
So I want to be able to operate for 48hr with a single radio (12VDC) at a 15% duty cycle (transmitting using 13A 15% of the time, and listening using 1A 85% of the time) using batteries and panels to charge them. I'll have about 14hr of daytime each day during the field day weekend. So I'm guesstimating 7hr of charge time each day. (I'm sure there is a better way to figure that)
Panel needs: So I'm calculating 85%*1A+15%*13A over 24hr would be 806.4Whr. With a fudge factor of 30%, I'm planning for 1048.3Whr per day. To put that back when charging, I'd need 1048.3Whr/7hr=149.8W of solar panels.
Battery capacity needs: absolute minimum would be to operate 24hr on battery only, assuming weather cooperates and I can get charging again during the second day. So for that 1048.3Whr/12V=87.36 Ahr, but this would completely drain the battery, so double it to stay above 50% and plan on 174.72Ah.
So I'd be looking at at least 150W of solar into a 180Ah battery string. I haven't read about charge controller sizing, so I'm making assumptions here.... On average I'm looking at 2.8A of current outflow. To put that back the charge controller should be able to handle at least 3A. (I've got a 10A charge controller kicking around in my solar learning sandbox)
my thoughts before I post and (hopefully) get all my mistakes corrected
- I did the battery capacity on 24hr because it is safer, but if I'm getting 7hr of charge time, can I calculate for 17hr of battery only operation?
- How different is real-life use from the basic calculations? Is that difference mostly encapsulated in the 30% fudge factor (no inverters involved, just DC)??
So I want to be able to operate for 48hr with a single radio (12VDC) at a 15% duty cycle (transmitting using 13A 15% of the time, and listening using 1A 85% of the time) using batteries and panels to charge them. I'll have about 14hr of daytime each day during the field day weekend. So I'm guesstimating 7hr of charge time each day. (I'm sure there is a better way to figure that)
Panel needs: So I'm calculating 85%*1A+15%*13A over 24hr would be 806.4Whr. With a fudge factor of 30%, I'm planning for 1048.3Whr per day. To put that back when charging, I'd need 1048.3Whr/7hr=149.8W of solar panels.
Battery capacity needs: absolute minimum would be to operate 24hr on battery only, assuming weather cooperates and I can get charging again during the second day. So for that 1048.3Whr/12V=87.36 Ahr, but this would completely drain the battery, so double it to stay above 50% and plan on 174.72Ah.
So I'd be looking at at least 150W of solar into a 180Ah battery string. I haven't read about charge controller sizing, so I'm making assumptions here.... On average I'm looking at 2.8A of current outflow. To put that back the charge controller should be able to handle at least 3A. (I've got a 10A charge controller kicking around in my solar learning sandbox)
my thoughts before I post and (hopefully) get all my mistakes corrected
- I did the battery capacity on 24hr because it is safer, but if I'm getting 7hr of charge time, can I calculate for 17hr of battery only operation?
- How different is real-life use from the basic calculations? Is that difference mostly encapsulated in the 30% fudge factor (no inverters involved, just DC)??
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