Hub motors and Hills

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Last seen: 14 years 5 months ago
Joined: Sunday, October 21, 2007 - 21:51
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Hub motors and Hills

Ive been working on my own custom built ebike for a few months now..

I hear stories and see advertisements for ebikes which can go upto 50KM on one charge.

I'm currently using a custom built 72V 18AH pack.. (the pack is only designed for short bursts of high 20 amps)
thats a peak performance of 1440W with a crystalite hub motor and a 20 Amp controller.

I hooked up an AMP meter to it one day.. going up a fairly steep hill... and noticed needle on the amp meter pretty much hit max 20 AMPS.

although my battery pack can burst 20AMPs for a few seconds it cant sustain that without shortening the capacity of the batteries.

I'm curious to see what peoples opinions about Hub Motors and hills are.

I live in a rather hilly area.. and my pack can only last about 9KM with peddle assist. for a ride which is generally up hill... a very gradual climb.. with a few very steep hills in between.

Am I better off Splitting the pack in 2 and giving it twice as much amp capacity and 36V...
I was thinking of making a switch.. which could switch from 72V down to 36V on hill climbs.
Does anyone know what the peak speed of 36V is with 16inch wheels?

Has anyone done this ?

I know that Chain drive motors have the advantage over hub motors on hills.. but they are also generally less efficient on flat and make a lot more noise.

Ideally if my pack was made up of high drain batteries and I rode the ebike on a flat surface with little to know wind resistance.. then I should be able to ride for an hour on a single charge..

but still going only 20-30 KM an hour thats only 20 - 30 KM..

I just don't see how mathematically any ebike can range up to 50KM unless its going down hill with a fit rider OR it has a 40AH battery pack.

a 60-72V 40AH battery pack using NiMh would be the size of a small suitcase..the kind that might hold a laptop.

with Li-Po it would be about half the size and half - 1/3 the weight.. and of course double the cost.

and I dont see how its possible with SLA batteries as that kind of capacity would break all the spokes on your back wheel.

any thoughts ?

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