A couple of weeks ago I set out on a 240-mile journey from my home in Ithaca NY to the New York Yearly Meeting (a Quaker gathering) in Silver Bay. Silver Bay is a resort on Lake George in the scenic Adirondacks. My vehicle of choice: a Surly Big Dummy cargo bike equipped with a Stokemonkey electric motor. I had made this journey last year covering the distance in three days. This year I planned to tackle the distance in two days, going 120 miles each day.
Last year my strategy was to charge my batteries en route using three solar panels supported over the rear of my bike. The solar panels were helpful, but couldn’t generate as much electricity as I needed. This year I upgraded my bike to use two 36-volt LiFePo4 batteries in series (for 720 watt-hours), and for this trip I carried an additional pair of 36-volt SLA batteries (for an additional 600 watt-hours). All of these batteries together weigh about 70 pounds.
I purposefully limited the amount of power my bike could draw from the batteries. My 72-volt system can easily push my bike over 20 mph, but at that speed my distance would be limited to about 60 miles. However, if I kept my speed between 10 and 15 mph I could get a full 120 miles out of my batteries, though I would have to be in the saddle 12 hours.Continue reading →