Originally Posted by
gauvins
1You don't generate meaningful current if you ride at less than, say, 12kms/h. Over hilly terrain, it is not uncommon to spend most of the time making very slow progress, and then barreling downhill just a few minutes, therefore generating almost no electricity.
It's just a question of what's meaningful current to you. Dynamo hubs generate current even at very low speed. You can see this when you walk with your bike and the LEDs emit light. That wouldn't be enough to supply your phone but a power bank might be able to trickle charge. And hopefully your tours aren't happening solely at that pace! That sounds like it would be a bad time to me.
My normal usage on tour is to have my phone in airplane mode while playing media and viewing offline maps. In that context the dynamo can get me to full charge in a few hours. I still carry a power bank to meet my needs in camp - usually reading, watching movies, audio/video calling, etc.