I am designing a system of 6 street lights .
initially opted for 10watt floods but i further searched and optimized to 3Watt flood lights .
They provide enough brightness for small street .
There was a issue of cloudy days, i down sized the battery capacity .
So initial units can get grid power as charging from grid is now cheap(low WH battery) .
Initial test:
Tested the led 230V driver out voltage :10.1V
230V-->driver-->floodlight
But i want to run the full set on DC , removed the driver and tested via linear dropping
resistor:
12V battery-->44Ohm dropper-->flood light
This gave current of approx 0.1Amps for a suitable brightness ,voltage across flood led 9.3V
[i know the dropper with electronics will be best,i will come to that]
As i didnot had 5W ,44OHM resistor so test resistors (.25Watt ) got heated and i had to abort the test
!
So I calculated
12V 7.5AH battery can source ...7hour approx @1AMP
same battery will give .............9hour approx @1AMP when led voltage is 9V
same battery will give ............15hour approx @.6AMP when we use six No.s LED [per led current .1A]
Conclusion:
Practically 10hour backup is possible ,cloudy days it will get a feed from grid.
Questions
a) is the calculation correct ?
b) 20Watt solar panel should be fine for the job as battery is just 7.5AH?
c) Will it be good to use a basic charger circuit, MPTT tradeoff may be 10%?
d) please suggest a dropper for 12V to 9V @.1AMP ,I am eyeing on options
- LM317 as CCS (tidy )
- few 1N4007 as dropper (cheapest)
-Fexible FET CCS http://bit.ly/1elYzGp :the FET ccs can also have a dimming via dumb 555circuit
initially opted for 10watt floods but i further searched and optimized to 3Watt flood lights .
They provide enough brightness for small street .
There was a issue of cloudy days, i down sized the battery capacity .
So initial units can get grid power as charging from grid is now cheap(low WH battery) .
Initial test:
Tested the led 230V driver out voltage :10.1V
230V-->driver-->floodlight
But i want to run the full set on DC , removed the driver and tested via linear dropping
resistor:
12V battery-->44Ohm dropper-->flood light
This gave current of approx 0.1Amps for a suitable brightness ,voltage across flood led 9.3V
[i know the dropper with electronics will be best,i will come to that]
As i didnot had 5W ,44OHM resistor so test resistors (.25Watt ) got heated and i had to abort the test
!
So I calculated
12V 7.5AH battery can source ...7hour approx @1AMP
same battery will give .............9hour approx @1AMP when led voltage is 9V
same battery will give ............15hour approx @.6AMP when we use six No.s LED [per led current .1A]
Conclusion:
Practically 10hour backup is possible ,cloudy days it will get a feed from grid.
Questions
a) is the calculation correct ?
b) 20Watt solar panel should be fine for the job as battery is just 7.5AH?
c) Will it be good to use a basic charger circuit, MPTT tradeoff may be 10%?
d) please suggest a dropper for 12V to 9V @.1AMP ,I am eyeing on options
- LM317 as CCS (tidy )
- few 1N4007 as dropper (cheapest)
-Fexible FET CCS http://bit.ly/1elYzGp :the FET ccs can also have a dimming via dumb 555circuit
Comment