Aha! A Freeloader add-on Freeloader AA/AAA Battery Charger ... but the Freeloader's construction shouts "break me! drop my bits in the road!" to me.
Correct. It has several serious drawbacks:
1/ the oh-so useful built in torch has a whopping great push button that is bound to drain the batteries if left at the bottom of a bag (stupid when it *also* has a slide switch for the LED)
2/ the power out connector is a proprietary easy-to loose cable
3/ the power out connector fairly quickly worked loose and became unreliable
4/ attempting to open the case to fix the above points was a fairly destructive process
5/ it won't reliably charge and be charged at the same time
6/ the battery compartment is a bit tight for the new-school oversized rechargeable AAs (but this is really the battery's fault)
7/ it gets very hot when charging.
On the plus side it is very small and (point 3 & 4 notwithstanding) fairly robust.
I've just received a
Powerboost pro2 charger. So far so good, it seems to not suffer most the issues above (but not yet tried 4 or 6!)
EDIT: I do also have the Extreme 4 battery charger. Not so keen on that one for touring as it's so much bigger, the batteries don't stay in when shaken, and again uses a strange USB cable.
All these chargers suffer the problem you have to charge in pairs; not ideal when all head torches seem to take 3 AAAs.