[newarts]

I think you should follow corfa's example & do a more quantitative assessment. Lithium batteries while expensive can perform extremely well depending on the application.

Total energy stored for Li-ion is noinally about 1/3 more than common batteries, but that's not the whole story. Li -ion batteries hold their voltage for much longer than other batteries so if your device stops working when the battery voltage drops below about 1.2V or the device draws a large current the Li-battery will last about 2-3 as long as others. This depends on the device; it won't make much difference for an led flashlight but it might make a big difference for a gps.

Here's a graph illustrating the differences: Battery Life

[normhead]

It depends entirely on your needs. When I travel, I have a GPS, a couple of flashlights, two cameras, etc, that one you posted looks pretty cool in that it's an all in one set up, but, the lightest setup I've used successfully is 6 watts output. That one is 2.5. So based on my previous experience, I'd guess it would take being in full sun all day to charge 4 AA's/ You can generally take manufacturers charge time estimates worth a grain of salt. They just take the maximum output of the device and tell you how long it theoretically should take. In my experience, actual performance in the field is from 1 tenth to one half of the manufacturers estimated performance. They never take into account the basic inefficiencies in the systems. Lighting conditions are not always perfect, putting 2300ma into a battery doesn't charge a 2300ma battery, I believe the best conversion rate is around 60%, I hate saying they intentionally lie... but, they know these things... they intentionally lie about performance.

Listen, honestly, I have put a lot of time and effort into making this stuff work.. and I own everything I need, although getting it cost me a lot more than I thought it was going to. I wouldn't recommend less than a 12 watt panel if you're going to depend on it. And if I totalled everything I own it would be well over $500. But unless you're going for more than 3 weeks, I would just carry extra batteries. How many batteries can you get for your $150? And how often are you going to do this? For one week trips to 10 days, my solar stuff stays home. It's just not worth the effort.