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Lighting from the solar power

This is very popular DIY.
Because of I've finished to make this unusually, then I do make this content.
I made a LED light from the battery power charged by solar cell.
I use my older solar panel rated 5W and measured 2.6W (11V at 47 ohms).
I use a charger that is bought in old day.

1. Battery and charger

At first I considered to use Nickel-Metal Hydride battery (NiMH battery) and considering about the charger as follows.
(I don't think to use lithium-ion battery because it become too complex about charger circuit.)

Sorry with Japanese in drawing, the left black box is a boost circuit and lower terminal is threshold.
Though I change mind to use deep cycle lead-acid battery, and then stop to make this circuit.
Because, the battery have a smaller output current capability for my purpose.
The brightness of fluorescent lamp will be 70[lm/W] and my purpose is about 2 of 20W fluorescent lamp.
Then I set my target brightness to 2000 lumens.
If I get 100[lm/W] by LED, it require 20W power.
The roughly maximum current of NiMH battery is 1C.
For example, the 1C is 1500mA=1.5A for 1500mAh NiMH battery or 1.3A for 1300mAh.
Then the maximum output power of for example 1500mAh one is 1.5A*1.2V=1.8W.
Considering with margin, NiMH battery is not so difference in cost compare to lead-acid battery, and smaller capacity,
then I decide to use lead-acid battery. I bought 12V/8Ah deep cycle lead-acid battery (WP8-12 of KUNG LONG).

2. LED

It require too many pcs if I use 20mA LED, and I can't find high efficiency 20mA LED.
It require special cooling system if I use high Watt LED.
Then I decide to use 60mA (3 chips in one) LED.
I select OSW44EZ4E1P of OptoSupply which says 25 lumens.
I estimate the functional brightness to 20 lumens, because the brightness of LED become dark by time
and it will be faster because this is made in China, and decide to use roughly 100pcs.
I divide 4 units, and 8 serial 3 parallel in each unit.

3. LED drive circuit

I make a boost constant current circuit by using MC34063 (compatible and MC34063L for some) as follows.

Because I get the parts from $1 USB cigarette adapter for car, some value of part is not ideal.
Please change each value if you try to make similar circuit by referring MC34063 manual.
I made the circuit board by using handmade CNC.


4. Result

Input power = 12V*0.45A=5.4W (not from battery but from power supply unit)
The measured 8 serial LED voltage is 23.5V. The constant current setting is 0.058A.
Then 23.5V*0.058A*3parallel=4.09W.
The efficiency of boost circuit (75.7%) is not good. May be it is because the parts value is not fit enough.
The battery output current will be 5.4W*4unit/12V=1.8A. 1.8A/8Ah=0.23C.
If the capacity to the cut-off voltage of discharge is 90% of 8Ah (=7.2Ah),
the maximum light time is 7.2/1.8=4 hours.
It's enough.
If the charge current is 0.75Ah/day at sunny, it is as a light time of 0.75Ah*60min/1.8A=25 minutes.
It is reasonable for me, because I don't go to my warehouse every day.

The brightness is 300 luxes at 1m distance.
It is enough brightness for my warehouse.
The case is also come from $1 shop, but the sheet under LED is changed
from paper to thin aluminum adhesive film on PP plate.
　 　

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