| Fairly low mileage but it also spends a fair bit of time inside. Most miles go on the unpowered one as the cargo bike (actually a rear-steer tricycle) is for large cargo. It's a nominal 200W panel (older fairly inefficient monocrystalline, big enough for a small sunshade which is its main function) and will fill the 1.1kWh battery in about a day (in a near-optimal climate), or two if the weather is meh. Before I mounted it on the trike I could get ~100-150km before plugging it into the panel on flatter ground or about 20-30km on a route with several big hills (12% grade) and a heavy (50kg bike + 50-100kg cargo + 75kg rider) load. The trike is pretty speed limited by handling though (20-25km/h) and it takes very little effort on the flat to keep it above the 25km/h speed limiter. On flat ground or shallow hills (1-2%) during the sunny part of the day (9-3) I can't use more power than the panel provides without going up hills because of the speed restriction. I'd imagine on a bakfiets in an area where 32km/h limiters were allowed you'd get about 30-50km depending on the terrain. Some back of the envelope: Consider this: https://www.bakfiets.com/elektrische-bakfiets/cargobike-clas... A less ghetto lid than my arrangement would be 0.63m^2 This would fit okay as a lid: https://www.solar4rvs.com.au/sunman-earc-100w-flexible-solar... a little narrow and would hang over the edge a little. Assume it's about 45 degrees from optimal (70%) and that you're getting the average irradiance from somewhere like denmark (1000kWh/yr). You'll get about 71kWh/yr. Cut off 7kWh for charging loss so 62kWh. A typical bike battery is 500Wh, so 120 charges or 1 full charge every 3 days. A charge might get you 20km or it might get you 90km, but for a typical rider with moderate hills who puts in a 40-60W contribution (same effort as walking) and doesn't want to risk grinding home the last 10km on a cloudy day, a reasonable ballpark is 50km/day. So you're looking at ~15-20km (but you'll need to charge it in winter), or maybe up to 5x that (and decent range even in winter) if you think very carefully about parking, live in a better climate for solar, and do 25 rather than 32. |