Hello CPF Community !
I am new here, it's actually my 1st post.
and the purpose of this message is to get some help ( classic..)
First, please note I am not LED expert,
The story is like this :
I have made a small solar PV offgrid system to power a LED flood light at home. Here the details:
INTRODUCTION
-I use 2x 3.2V 20Ah Lithium 0.33C LiFePo4 batteries togeher in serie
it gives me 6.4V 20Ah
-I use a solar controller 5A 6V
-The LED flood light I use is rated 6V 6W 1A. ( but I have some doubts)
So I connected everything together to light my garden at night. The controller is set for 6 hours. It has been a while since the 1st trial..about 7 months running everyday.. Some facts :
- The LED is still very bright at the beginning of the night.
- 2-3 hours later it starts dimming. when we reach almost 6 hours of use, it's hardly on..it's very very weak
QUESTIONS:
what is wrong with my system ? why the LED cannot be bright 6 hours ?
in terms of safety of discharge, i feel we are good :
- Battery 0.33 x 20Ah = 6.6A and I use only 1Ax6hours = 6A in the night.
in terms of watts, I feel we are good too..
6Wx6hours = 36 Watts per night .
Battery has 6.4V x 20Ah = 128A
If I draw 50% of the battery i can run 2 nights ( 2x 6hours) without charging but everyday it does ( may be not fully, but I assumeI get 3-4 hours of sunshine at least, which gives me 3 hours x 5A = 15A everyday. and LED only uses 6A everynight..
in terms of solar panel:
I use 3x 6V 10W solar panels in parallel . so total is 30W 6V ( and 5A)
Today , at noon, it was cloudy and my charging voltage was 6.17V ( solar panel side)
the charging voltage for batteries was 5.84V
I measure directly on the solar controller's bolts.
At the beginning of the night, when the LED is bright, the measured voltage is 5.77V
When it dims and is very weak, the measured voltage is 5.14V
How is it possible ?
My solar controller is supposed to have a discharge cut off voltage of 5.4V. So, how come the LED is still on with a voltage of 5.14V ?
I try to understand what is wrong but I cannot see throught ..
is my battery dead ? I doubt it..and it's Lithium LiFePo4..
is it not enough solar power to charge ?
What would you change to get 6 hours of brightness everyday ?
Thanks : )
Frank
I am new here, it's actually my 1st post.
and the purpose of this message is to get some help ( classic..)
First, please note I am not LED expert,
The story is like this :
I have made a small solar PV offgrid system to power a LED flood light at home. Here the details:
INTRODUCTION
-I use 2x 3.2V 20Ah Lithium 0.33C LiFePo4 batteries togeher in serie
it gives me 6.4V 20Ah
-I use a solar controller 5A 6V
-The LED flood light I use is rated 6V 6W 1A. ( but I have some doubts)
So I connected everything together to light my garden at night. The controller is set for 6 hours. It has been a while since the 1st trial..about 7 months running everyday.. Some facts :
- The LED is still very bright at the beginning of the night.
- 2-3 hours later it starts dimming. when we reach almost 6 hours of use, it's hardly on..it's very very weak
QUESTIONS:
what is wrong with my system ? why the LED cannot be bright 6 hours ?
in terms of safety of discharge, i feel we are good :
- Battery 0.33 x 20Ah = 6.6A and I use only 1Ax6hours = 6A in the night.
in terms of watts, I feel we are good too..
6Wx6hours = 36 Watts per night .
Battery has 6.4V x 20Ah = 128A
If I draw 50% of the battery i can run 2 nights ( 2x 6hours) without charging but everyday it does ( may be not fully, but I assumeI get 3-4 hours of sunshine at least, which gives me 3 hours x 5A = 15A everyday. and LED only uses 6A everynight..
in terms of solar panel:
I use 3x 6V 10W solar panels in parallel . so total is 30W 6V ( and 5A)
Today , at noon, it was cloudy and my charging voltage was 6.17V ( solar panel side)
the charging voltage for batteries was 5.84V
I measure directly on the solar controller's bolts.
At the beginning of the night, when the LED is bright, the measured voltage is 5.77V
When it dims and is very weak, the measured voltage is 5.14V
How is it possible ?
My solar controller is supposed to have a discharge cut off voltage of 5.4V. So, how come the LED is still on with a voltage of 5.14V ?
I try to understand what is wrong but I cannot see throught ..
is my battery dead ? I doubt it..and it's Lithium LiFePo4..
is it not enough solar power to charge ?
What would you change to get 6 hours of brightness everyday ?
Thanks : )
Frank