The larger one will charge the phone one and a bit times, and the smaller it to make sure I have charge for my watch. In principle it's enough for 5 or 6 charges but I still need to test it.
The dark horse is the solar panel. Its a back up I suppose, in case I don't reach a place to recharge. But is it worth the 80g?
The panel is from Lixada - cheap but with a simple fairly rugged design with just a socket for a USB cable. Nominal output is 10 Watts. 2 Amps on 5V would charge the 2700 mAh phone battery in an hour and 30 minutes. But life's not that simple. Firstly the device has a rated output of 1700mA at 6.xV. - but at the USB port only 1200mA max. on 5V. So in practice it's a 6W panel.
How much current does the panel actually deliver? When I've tried indoors at the windowit has seemed fairly ineffective. The charging light comes on on the phone but the charge status doesn't move noticeably - if anything it discharges! But with good sun (for springtime in Sweden) it does charge a powerbank battery - slowly.
What's going on? How good or bad is it? I did a quick search on Google play and downloaded a battery app that can show charging current and put the panel and phone out in the sun.. Slightly intermittent sun...
The first thing is, with the phone screen on, apps, wifi and mobile data running the panel doesn't keep up with current drain unless there's good sun, and then only just.
But if the phone is not drawing much current? With the phone in flight mode and the display off it managed about 250mAh in 58 minutes. At that rate, eleven hours for a full charge and its giving around 1.2W. There's still some drain in the phone. Charge it turned off and that's probably 'only' nine hours for a full charge.
On the other hand, on YouTube a guy shows it delivering 700mA to a Power bank. That could give a useful 25% charge in an hour and still not much over half the rated output.
The differences could be three things, how much sun its getting, whether my unit is as efficient (it should but who knows?) and whether the panel is better able to drive current to a bank rather than a phone. Four things... The phone is measuring current into the phone battery - not the current from the panel.
Conclusively inconclusive. If more sun gives a better charge rate then it is worth having - albeit if you're stuck up a mountain in pouring rain it's not going to help at all! Even as it is topping up the phone 10% over a lunch stop is good to have.
But a bigger powerbank could be a better bet for the weight.
More testing I think and see if there's more juice to be had from more sun. :) Or maybe add a tinfoil reflector? :D
Update: new tests on a sunny slightly hazy morning gave an average 560mA over 20 minutes and a 7% charge. Over 20% per hour is starting to sound interesting :)
