Below are data collected on the charging behaviour.

The whole exercise sparks from the observation that MPPT solar charger recording a mean 6-9W Solar output from my 2 x 150W solar panel in full sun coverage. It strike me that when the battery bank is full, we don’t pull the full power out from the panels. I want to know how much power the solar panels can push out at different time of the day, especially when I’ve only 3-4 hours of direct sunlight, is it sufficient to charge up my battery bank.

[table] Time,Panel(W),Battery(V),Load(W),Charging(A)
08:00,8,-,32,-
11:00,17,11.8,32,-
12:00,24,11.6,32,-
12:30,32,11.7,32,-
13:30,48,12.1,35,0.7
14:20,72,12.6,39,2.4
15:10,92,13.0,43,3.6
15:38,140,13.3,47,6.5
17:30,14,12.5,37,0
17:50,12,12.4,37,0
18:15,6,12.2,35,0
18:45,0,12.0,35,0
20:10,0,11.3,24,0
20:40,0,10.2,21,Beep
08:00,9,11.7,0,0
09:00,15,12.0,0,1.1
10:00,23,12.3,0,1.6
10:30,23,12.4,0,1.6
11:00,18,12.5,0,1.3
12:20,30,12.9,0,2.2
12:50,40,13.1,0,2.8
15:30,7,13.4,0,0
17:14,6,13.5,0,0
[/table]

I’ve 2 X 12V7.2Ah battery in the bank ~ 14.4Ah.
Day 1 test, Battery provided power to the LED strip after sun down for 3 hours. est 8.7Ah (2.9A for 3Hr), about 70% drain.
Day 2 charging, without load, both battery got fully charged well before 3pm. All this without direct sunlight.

The Panels should have lots of juice left to charge more batteries. Will build a bank of 10×7.2Ah battery to provide 12hours growth light for this system.