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I am attempting to create a charger from a solar panel that outputs power through a USB port. I have a 10W 12V solar panel. I tested the solar panel on a sunny day and it outputs 17V and .5A. I also bought a USB charger that plugs into a 12V car outlet. I figured I could just connect the solar panel to the USB charger and charge my phone, but this didn't work. I would like to know if adding a battery to this arrangement would solve my problem? Also, I was wondering if someone on this forum could describe a simple way to create this USB solar charger?
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That makes a nice little project to get started believe it or not, but you'll want two additional components.
Yes, grab a battery. A small sealed AGM type of about 3 to 5 amps maximum would do nicely. Between your 10 watt panel and the battery should go a charge controller. I think a Morningstar Sunguard 4.5a PWM type would be perfect.
Your 12v - 5v usb adapter can attach directly to the battery, if it hasn't already been smoked by the direct application of the panel. Maybe you'll want to wire up a cigarette lighter adapter to the battery to slide the usb adapter into.
The fun part is grabbing a decent multimeter, and after charging the phone and letting the battery rest for at least a few hours, take a voltage reading. From the info here, you can kind of determine the state of charge of the battery, ie 12.8v+ = full charge, 12.6v = 75% charged, 12.2v = 50% charged. You don't want to really go below 50%, although one could argue that a 5ah agm is cheap to begin with.
SAFETY - even at these relatively low currents, you still want to respect it - don't drop anything across the posts, or wear jewelry while taking measurements etc.
It is a simple way to start, yet provide enough fun feedback to be useful. Before long, you'll be thinking up higher-power applications... -
Yes, although you would also need a charge controller at that point. It can be really simple (a 15V 1W zener with a heatsink for example, or a 7815 to regulate down to 15V.)
A simpler way might be to use a linear regulator. The venerable 7805 (Radio Shack sells them) will regulate the 12V down to 5V. There's a schematic of how to connect it on the back of the package. At your power levels you could see as much as 6 watts of dissipation so use a good heatsinkAlso, I was wondering if someone on this forum could describe a simple way to create this USB solar charger?Comment
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