I have a sensor in a remote area that draws 15 mA @ 6 V for 16 hours each day, powered by a 6 V, 1100 Wh low discharge battery. I'm trying to achieve around 2 years of autonomy.
Daily consumption is 1.44 Wh (6 V x 0.015 A x 16 hours), so I'll need around 1051 Wh for 2 years. Assuming a discharge of 70% of the battery before replacing it, my power budget is around 1502 Wh, too high for my 1100 Wh battery.
I have a small 6 V, 1 W solar panel laying around so I thought I could use it to charge my battery. I made a simple test with a small 6 V lead acid battery on a sunny day (not too bright) and measured 6.9 V @ 70 mA when charging, so on a full sunny day at the peak I guess I can get more than that. To be conservative, I'll consider 6 hours of sun each day @ 70 mA, or 420 mAh per day. My sensor draws 240mAh per day, so at least in spring/summer I could expect to not drain the battery and also charge it a little bit (I guess).
So my questions are:
- Will this small panel make any difference charging this battery?
- Is it OK to connect the solar panel directly to the battery? (I'll add one Schottky diode to prevent discharge during the night)
- Since the battery is expensive, is there any chance a faulty solar panel could destroy the battery (broken panel, short circuit...)?
Any other ideas are welcome. Thanks