|The Finished Solar Backpack!|
Last year , i was trekking in the mountains and was surprised by the lack of electricity. Although there was an abundance of sunlight during the day, all lighting there during the evenings/night was with oil lamps which not only smoky but provided very little light. Vowing to return next year better prepared, i made a solar backpack. It can be also used to power widgets such as the arduino, raspberry pi, etc. Here are the features:
- Can charge upto 6 mobile phones at one time!
- 140 lumen high power led lighting
- 27wh high capacity battery
- Modular Design for expansion
- 5W Solar panel for 6v battery
- Old Bag / Bagpack
- General Purpose PCB
- Schottky Diode (1n5189/ SS14 etc)
- 6v Sealed Lead Acid battery
- 2 pin Terminal plug
Solar Mobile Phone Charger Circuit:
- 5v 3A LDO (I used a ucc383. You can use an LDO with a lower current capacity also)
- Heatsink for the TO-220 package LDO
- USB Port
- High Power led (Can be 1w-3w. I used a CREE XM-L as it is the most efficient led the world)
- Heat Sink for LED
- Lens/Reflector for the LED
- LED Driver
- Attach the solar panel to the backpack. You can stitch it, use hot glue, epoxy or any other adhesive as you see fit. I used a synthetic rubber based adhesive called FeviBond.
- Using a general purpose board, construct the following circuit:
Circuit Diagram for solar backpack
PCB of Solar Backpack
- To make the light engine, i soldered some wire to the Cree XML led and mounted it on the heat sink.
- Although the Cree XML can be driven with 3 Amps or current giving a staggering 1000 lumens, i could not find a suitable driver. Hence, i am using a 350ma driver.
- Some LED drivers, for use as halogen replacements have a bridge rectifier.If you wish, you can remove the diodes as they cause a voltage drop of about one volt. I removed them as they reduce efficiency
- Mount the led driver on the other side of the heat sink
|Led Driver mounted on heatsink|
- Attach the reflector or lens to the led.
|Reflector mounted on the led|
|Mobile phone being powered by 100% solar power!|