znomit : I have seen all the work you have done with dynamo hubs. You have extensive real life experience, my little knowledge is still purely based on theory and based on reading about what other people have done (including yours, thanks for that). So I can only agree with what you bring up here. What is the most economical and practical solution does indeed depend on the conditions it will be used in. An external battery pack or even 2 will be cheaper than a hub plus charger. The only disadvantage I see is that with external batteries, you still have to make sure that they are charged when needed. The hub and charger is hassle free.