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Cheap Electric fatbike
PonoBill:
I tagged this onto the downhill video, but shouldn't have. Just being lazy.
Here's my latest project. Built this yesterday. It's a cheap fatbike ($250 from K-Mart) mated to a REALLY good Chinese crank drive electric. These Bafang BBS02 drives are beautifully engineered. This is the new 100mm, version that fits most fatbike bottom brackets. I had to cut 15mm off my braket to fit it, which would be shameful with an expensive fatbike but for $250 it's no biggie. The power electronics are in the drive, so there's just one waterproof harness for the control circuits, one for the battery and one for the speed sensor. Super clean installation and a TON of power. 1200 watts peak, 750 continuous. Highly configurable and very good UART control system (tons of info available on line). Or just stick it together and ride with default settings (like limited to 20MPH). Super powerful, especially with the seven speed gearing on my cheapo. Even has discs.
The 100 mm versions are hard to come by here, no one wants to ship them to Maui, so I bought 11 of them straight from Bafang and imported them. If someone wants one on the Hawaiian Islands I'll sell it to you at my cost. I don't know exactly what that is, but it's somewhere around $600. I had plans to do something exotic with them, but other priorities arose. If you're on the mainland you can get these pretty easily for about $700, but be sure you're getting the right length for the bottom bracket. Standard is 68mm, but most fatbikes are either 100 or 112.
Got to be the cheapest way possible to build an electric fatbike with a quality drive. I'll never build another hubmotor bike--too clumsy. The K-mart here in Maui has three of the model I used left in stock.
I'm using three 14.8 V 5000ma RC LiPos to power mine. Super cheap way to do a fatbike battery if you already have a 4 channel LiPo charger. I already had four of the batteries for multicopters. The photo shows 4 but I had to drop to 3--the drive errored out from overvoltage. Nice that it just says "sorry, can't do that" instead of just toasting. I'm eventually building a set of three batteries that will sit in parallel with two sets diode-isolated and one switchable as a spare. With 15 amps at an actual 50V it should give a lot of range. . 750 watt/hours, or about an hour at full power. More like two hours at 20 mph. Kind of bitchy to charge, but a few hundred bucks less than a standard bike battery and much lighter.
Subber:
Nice!!!
Looking forward to the Ride Report.
PonoBill:
Rides great. I can break the rear wheel loose in dirt. Very zippy and super smooth. I don't like how the pedal assist system works. It's backwards. If you pedal lightly it supplies more power, when you pedal hard it backs off. I'm going to disconnect that or change the parameters in the controller. I prefer to throttle the power anyway. I think the automatic stuff is kind of dangerous.
I have the speed cutoff set at 20mph and the bike reaches that really quickly in second gear (with five to go). So I'm going to set that to thirty, though thirty MPH seems like time for a full helmet not just a bike one.
Got to say I LOVE the fat tires. Ways smoother than suspension bikes. Going to be fun on sand. It would be great in snow too.
covesurfer:
I gotta come over to Ponohouse and ride that thing. Seriously. I want to try it out.
LB Surper:
Curious, how are you packing the batteries so they don't get damaged while riding?
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