As you probably know, I'm going down the hardcore homebrew route with a view to integrating everything into one box. I've got a
working prototype of the
insanely efficient active rectifier - no voltage drop *squee* - (for extracting useful power from a hub dynamo at the sort of pace I could expect to manage fully loaded back when I spent more time breathing solder fumes than riding bikes) and USB charging sections. I've used this successfully to keep my ageing smartphone in power on various trips this summer.
The next stage is to add some logic to deal with excess voltage from the dynamo at speed (it's currently dissipating excess power as heat, which is wasteful and tends to toast the zener diodes on fast descents) and a battery pack. While my Nokia is happy with an intermittent charging source, other gadgets seem not to be, and it makes things more flexible to be able to store a couple of phones worth of charge.
Adding solar and mains/12V inputs should then be straightforward. I think I do want a solar panel for days that involve more camping than cycling, but I've yet to work out what to use. Depends on whether I'm aiming at small devices, or running a netbook (which I reckon is just about doable, assuming it's mostly going to be used for short GPS and photo wrangling sessions, rather than prolonged spodding). There are some
utterly droolworthy flexible 5W panels out there.
I was considering using AA NiMH cells as the battery pack, with a view to being able to charge the ones from my GPS/torch/etc. But it seems that building the sort of multi-channel NiMH charger that entails is going to mean a lot of inductors and stuff that add weight and complexity. It seems better to have a large lithium-ion/lithium-polymer battery pack with a single charging channel, and deal with AA/AAAs externally with an off-the-shelf charger.
I discovered the
SCH600F charger, which meets the fairly restrictive requirements of running from a 5V supply at dynamo/solar-friendly currents while having independent charging channels for the cells - nearly all USB-powered chargers charge cells in pairs for simplicity, which is useless when you've got devices that run from 3 AAAs. It's cheap and plastic, but is surprisingly lightweight and does what it says on the tin. It needs minor fettling to make it touring-ready, in the form of disconnecting the 'refresh' button internally, as that's just going to get knocked and waste all your valuable charge, and the addition of a Mk 1 elastic band to hold the battery compartment flap shut.