Comments on: How to Make a Cheap USB Solar Charger

By: pr

pr — Sun, 04 Jan 2009 08:40:49 +0000

Photovoltaic cells produce current proportional to illumination. The voltage is dependent on temperature, going up as it gets colder, but it’s a pretty shallow slope. So it won’t overvolt just because the sun is shining, in fact the voltage goes down because the cell gets hot.

Adding a regulator to this thing is going to cut it’s production a lot. A 7805 regulator has two diode drops, i.e. if you want 5 V, you have to feed it 7.2 V. Maybe a 5 V zener across the output would be a better way to limit voltage, but at some point the current would blow it up.

Whether a little extra voltage would matter depends on what you’re putting it into. Ordinary electronics won’t care. I accidentally ran my 2-AA CD player on 7.5 V for an extended time, and it didn’t care a bit. Ni-Cad’s and NiMH’s won’t mind being overcharged a little bit, either.

Lithium ions are much more sensitive to overcharge, which is why they usually carry their own protection circuitry, so again a feeding it a little extra voltage won’t be a problem.

By: Spyros

Spyros — Fri, 01 Aug 2008 12:28:43 +0000

The only problem is that you have to have sorar panels that give the exact power that the battery requires to be charged according to its manual or else it will be destroyed after two-three times of being recharged that way.So it can be used only in case of emergency..
Despite that i have to say that it’s a brilliant idea.Keep on!

By: clifford

clifford — Mon, 28 Jul 2008 13:48:57 +0000

can any1 teach me how to make one?

By: DaCheetah

DaCheetah — Sun, 18 Nov 2007 00:15:52 +0000

Grrr. Am I the only one who really hates it when people say “sodder” instead of solder?
(I’d also have thrown in a cheap 5v regulator just incase the cells were putting out more than 5v on a sunny day, some USB stuff is rather sensitive.)

By: Nanosolar PowerSheets

Nanosolar PowerSheets — Fri, 16 Nov 2007 20:05:30 +0000

[...] am a huge solar technology fan as I have mentioned before and so nothing makes me happier than to see new technology being developed to make solar power [...]