mbs wrote:i'm wondering if you guys have any suggestions or any idea of the best hub motor today?
Federal law in the United States states that an electric bicycle must have a top speed when powered solely by the motor under 20 mph (32 km/h) and a motor which produces less than 750 W (1.01 hp).
amberwolf wrote:That's not federal law restricting all ebikes. That's the federal CPSC regulations about what can be manufactured and sold as an (low powered) ebike (for use on public roads).
People keep posting that up as if it was "the law". it's not. Each state and locality has different ones.
mbs wrote:the best direct drive hub motor in terms of efficiency(base on its efficiency curve). i'm trying to build my own ebike right now and if it's not too much to ask, i'm wondering if you guys do know or can suggest other direct drive hub motor that has a great efficiency.
Jeremy Harris wrote:mbs wrote:the best direct drive hub motor in terms of efficiency(base on its efficiency curve). i'm trying to build my own ebike right now and if it's not too much to ask, i'm wondering if you guys do know or can suggest other direct drive hub motor that has a great efficiency.
Again, it depends entirely on what you're going to do with it.
We need more information, I'm afraid.
- The size of the wheel you're going to fit the motor into has a massive effect (because diameter determines motor torque and motor torque is directly proportional to current and current is the single biggest driver when it comes to motor efficiency).
- The total weight of the bike and yourself (because weight determines the power needed to climb hills and accelerate and so also the torque requirement and hence the current and efficiency, as above).
- The maximum speed on the level that you want to go (because speed determines rpm and rpm is determined by the motor velocity constant and battery voltage, and the velocity constant is determined by the motor winding, which has a direct impact on motor resistance and hence efficiency at any given torque).
The simulator on the Grin web site, here: http://ebikes.ca/simulator/ is a really good starting point to play "what ifs" with, and may help you understand how efficiency varies a great deal with load.
mbs wrote:yes! i'm currently looking for a 20 inch diameter, and operated at 48v. i did already look at their site before, it seems that 9c 2807 would already fit my ebike project but i'm still in search for a better motor(efficiency curve) right now.
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