Best Wishes,
Mike

But really, I think there’s a greater threat of thermal damage from leaving it in the sun than from overcharging li-ion batteries with 80 ma.

The only real drawback is fairly obvious:
Extremely low current (amps) will result in very long times to charge.

Still, if you mounted 2 of these on an EEE PC and wired them in parallel, you could get an effective juice of 12v at around 0.2 Amps… not too snappy for a couple modules, but if the 3 amp output of the DC adapter means anything, that would give an amp hour every 10 hours (less from losses) of direct sunlight.

I don’t think it’s worth it, really, but it would only cost about $80 to find out, potentially.

Personally I would look for better modules before settling on those ones. I also might consider a fold-out design of home-made modules (from broken ones, of course) to provide more power than needed, using some charge controlling and blocking diodes to account for other issues that might come up… but that’s not exactly super-portable like the EEE PC intends to be.

for best results use a usb inline battery backup

People with questions could go to the instruct-able and ask for more details there. That that is where the project and maker/user are active, after all.

Thank you to the creator of this project for clarifying some of the details on this project by visiting this site.

Eee PC solar project:
Yes, there is enough space to put panels on the back side of the display, but it would make the device thicker (bigger) which appears to go against part of the “small ideal” which is one of the Eee’s selling points.

Lipos come in all flavors, raw cells, cells w/ under-/over-voltage protection, some have charging circuits however they also have additional leads. So, if your cell only has 2 pins, there is no built in charging circuit.

As for protection, I can only confirm that there are, in fact, batteries with no protection at all.

80mA won’t make anything explode (those things typically charge at 1,000s of mA), but it will certainly damage the cells (ie. they will have a shorter lifespan)… Basically the same mjn said :-P

(Disclaimer: I design high-power flashlights, so I know the batteries there, ie. round batteries. I assume square batteries are more of the same.. Would be weird if they weren’t)

(Also have in mind that open-circuit voltage != actual in-circuit voltage)

This circuitry is built into some packs, not others. I’ve yet to see a modern laptop battery pack without this circuitry. I’ve never seen a cell phone battery with a built in protection circuit. Typically they have a built in temperature sensor – hence the three terminals that most cell phone batteries have. I’ve never taken apart a DS battery – but I highly doubt they have built in protection circuitry. Not in that form factor. No way.

OK with that out of the way – how do you typically charge li-ion or li-poly batteries? Well – most circuits give them a constant current with a voltage limit. Most packs can handle 1C or higher. So what this means is that you start out charging at your set current but as the pack gets full its voltage approaches the voltage limit and the charge current slowly tapers off.

Now – this guy’s circuit just connects a current source to the terminals of the battery pack. It is a weak current source, but it still is a current source. This means that he is in fact overcharging his cells, albeit slowly. Will they explode? I bet if you left it out in the sun on a hot day the pack would puff up. He’s certainly doing damage to the pack – but how much is just too hard to say.