Solar USB charger

jonr

I need a small (5W or 10W) solar panel to charge a cell phone.  I first looked at complete systems, but people reported that they didn't work well (not enough power to fully charge).     Then I looked at a more DIY solution using a small PV panel plus a buck voltage regulator - but that would suffer from voltage collapse under low output conditions.     I finally ordered this regulator; it has an input voltage adjustment (ie, manually adjusted MPPT). 

http://www.ebay.com/itm/BQ24650-MPPT-Solar-Panel-Lithium-Lead-acid-Battery-Charging-Board-Controller-5A-

Will be interesting to see how well it works.   The same regulator might also be useful for powering some small DC pumps (< 5A).  Or charging small lithium batteries.

Photowhit

Not sure why you would want or need one of those charge controllers. Your cell phone has a perfectly good charge controller built in... I have some 5 watt 6 volt solar panels and added a 5 volt voltage regulator that handles up to 1 amp, and a sub outlet from a computer. It becomes a source of power that charges even picky usb charging devices such as my old Nokia N800 (pocket computer/thingy)

I've also heard and seen, I guess at Pinterest, of people doing the same thing with a small maintenances car battery panel (VW use to ship them with a suction cup to the car windshield. and a car lighter usb adapter. It sounds simple and effective. Of course ready made solar usb power sources aren't too expensive by them selves, usually less than 5 watts though.

jonr

Despite the label, it's a voltage regulator, not really a charge controller.   A normal buck regulator (probably what you have) doesn't do any form of MPPT.  So when the phone tries to draw more than the panel can put out, the voltage will collapse, probably to well below optimal (MPP).    That may still work, but slowly.     Would be interesting to check your panel voltage under various light conditions.  Around 8V should be optimal.  If it gets dragged down to 4V, then it becomes a ~2.5W panel.

Photowhit

Voltage regulator, picture is a link;


USB's come in all sorts of amperage, originally they were usually no more than .5 amps, so the charge controllers work fine with the old usb specs. The Nokia was very temperamental and didn't work on some cheap usb wall warts I had purchased from China, but worked fine on my quickly cobbled together charger.

Buy and spend what ever you want, I know this works.

I gave the original away with the Nokia, but I have made another for someone else and have the pieces, though I'd have to strip a usb out of a computer or find a usb extension (I think I saw one around recently) I'll even will send you the pieces for the cost of postage!

jonr

A linear regulator makes a 5W @ 8V panel into a 3.4W @ 5.5V panel - at best (without collapse).     Far worse with the 5W @ 17V panel I have laying around.   But I agree that there are lots of ways that will eventually charge a cell phone.

I see some indications that newer cell phones with Quick Charge 2 or 3 might tolerate and make use of up to 12V.

Johann

Use a smaller solar panel and put a smaller charge controller on it. Charge one of those cheap $ 15  12volt 7ahr batteries and hook up a car plug. Get one of those car USB that plug up to the car plugs/cigarette lighter plug and you are in business.

Now you have USB power all day and night.

mcgivor

Johann said:

Use a smaller solar panel and put a smaller charge controller on it. Charge one of those cheap $ 15  12volt 7ahr batteries and hook up a car plug. Get one of those car USB that plug up to the car plugs/cigarette lighter plug and you are in business.

Now you have USB power all day and night.

Thats what I did, cage 2 phones and a tablet via 3 way adaptor, battery lasts about 4 years.