That is the role of the “USB Smart Adapter”, somehow it tweaks the USB ports by changing their mAh ratings to deliver the requirements of the appliances being charged (probably within certain limits).
My Ipad Mini requires 5W only. And as I mentioned before I HAVE BEEN ABLE to Increase the battery reading on my Ipad Mini by 17% (i.e from 60% to 77%) using two fully charged AA Batteries.
Powerpacks or just bringing extra set of batteries is definitely a good / lightweight strategy. In my case I do enjoy outings in very cold environments so I need to be particularly careful about keeping batteries warm so they don’t lose their charge, because if they do, that’s it.
Still the idea of harvesting solar power is very appealing to me, for environmental reasons and as a potential UNLIMITED source of power. The tricky part is to have a lightweight system that actually works.
The Powerfilm USB+AA has been reported to be effective charging its two AA batteries even in not ideal conditions. Manfred Kopish has several mentions on these forums of successfully using this product on the field. I bought this product under the assumption that I would be able to power only small devices (i.e Steripen, GPS, Headlamp, camera, etc). Then I run into the “USB Smart adapter” which somehow tweaks the limited output on the Powerfilm USB+AA to deliver more juice than its manufacture’s specification.
Without the USB smart adapter I don’t even get a “charging signal” on my Iphone 4s or my Ipad Mini. If I plug the “USB smart adapter” into the USB port of the Powerfilm USB+AA I DO get a charging signal on my Ipad Mini and have successfully transferred juice to bump its battery at least by 17% points every time so 4 AA batteries (two at a time) should allow me to increase the battery in my Ipad Mini by 34% points, which is more than what I need (and all this without using the sun at all, which of course I intent to use).
So I have to test this in the field, but my plan is to bring a couple of sets of AA Batteries (1 set = 2 batteries) and have them permanently charging while I hike (2 AA at a time). I should be able to get 4 AA batteries fully charged by the end of the day. This gives me 10,800 mAh (4 x 2700) of renewable (on the field) power everyday. (Even if is every OTHER day, that should work fine for my needs). What is the weight penalty: 4.8 oz (4.5 oz for the Powerfilm USB+AA and 0.3oz for the USB Smart adapter). I’m not counting the weight of the 4 AA batteries since I was bringing them anyway.