Joined: Jan 2009
Posts: 44,341
Likes: 6,641
From: New York, NY, and High Falls, NY, USA
Bikes: 1962 Rudge Sports, 1971 Raleigh Super Course, 1971 Raleigh Pro Track, 1974 Raleigh International, 1975 Viscount Fixie, 1982 McLean, 1996 Lemond (Ti), 2002 Burley Zydeco tandem
I took a nine-hour one-day ride last summer and used a one-pound external battery. I used it for charging a few things, one at a time. I had a USB-chargeable headlight, a tablet, and a smartphone. It was more than enough. I think the rating on the battery was 20,000 mAh.