I am pulling my hair off over this problem.
Will greatly appreciate any clue, hints, comments, no matter how small.
My remote unmanded anemometer station total load is 450mA. It is powered with a 44W solar power panel. I use a 70AH 12V battery(1). So the battery should last 70AH/(450mA*24H)=6.5days in total darkness. I am not using a battery charging regulator, so the 44W solar panel(2) charge directly to the battery without going through a regulator.
For the past 3 weeks, it has been rainy and cloudy in Singapore but occasionally with 1-2 hours strong sunshine per day.(3)
These few days, my system went dead at 2-4am, and starts up again at 9-10am, indicating battery flat during nighttime.
I am puzzled by this, by experience of other suppliers a 5 days backup battery is normally adequate for Singapore weather even in rainy season. The yearly average peak sunshine hours of singapore is 4 hours.
I am thinking alone these angles and probabilities, what do you guys think? :
a. I did not install a battery charging regulator, thus during cloudy days, the battery cannot be charged properly and thus wear out quickly. The battery has only been in operation for only 3 months. The regulator was not supplied by system maker saying that for this small current solar system it is not needed.
b. The solar panel is bad in quality, and thus cannot charge the battery properly. I am not sure who and where is the manufacturer(china maybe?). But other Japanese brand is twice as expensive.
c. Though I placed 500g of drying agent in the panel box, but I am thinking that the high humidity caused small current leakage in the system and thus battery power dissipated more quickly.
d. The battery is bad in quality?
e. THe anemometer is outputting 4-20mA to a datalogger/modem. I used a 4-20mA signal multiplier and branched the 4-20mA signal to another datalogger. THe multiplier is eating a lot of power(about 2x,3x the original system). Since we have put in this new multiplier and a larger battery, we have been having battery flat problem. I dont have any rational clue but the multiplier "feels" very suspicious.
Did I miss any angles? What is your experience?
(1) Battery specs: geocities.com/bambinorama/YC70-12.pdf
(2)Solar panel specs:
(cascade two pieces)
Nominal Max output(PM) 22Wx2 (@1kW/m2.25degC.AM1.5)
Nominal Open circuit Voltage 18V
Nominal short circuit current 1.65A
Nominal Max Output Voltage 14.4V
Nominal Max output Current 1.5Ax2
Nominal weight 3.0Kg
(3) Singapore pass twenty days weather summary: http://www.wunderground.com/history/station/48698/2008/8/9/MonthlyHistory.html http://www.wunderground.com/history/station/48698/2008/9/9/MonthlyHistory.html
A typical cloudy day: http://www.wunderground.com/history/station/48698/2008/9/6/DailyHistory.html