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Charger Bike
Are you using the same chain driven by the pedals as the one driven by the motor? ie, 1 chain and not 2.

Maybe some pictures could help see your setup.
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Here are a few pix.  The motor is in a plastic fairing above the pedals.  On the rear wheel, there are two sprockets, one for the pedals, one for the motor, both on the
R/H side of the nexus7 hub.  

Please excuse the messy install - I was just in a hurry to see it work Smile.
I think the most practical fix would be to put a freewheel on the pedal sprocket. And I'm sure I can't buy such off the shelf. I'll have to remove the plastic fairing and see what's inside, and how much space there is. Hopefully enough so I can shoehorn something in. I do have metal cutting and welding capabilities. And a pedal
crank turns pretty slowly, so it doesn't have to be exquisitely balanced.

Am thinking to get the go-kart freewheel that I saw on Amazon, get a new pedal sprocket, cut out the inside and MIG weld it to the outside of the freewheel. Or something like that.

... and a quick google shows that it *might* be possible to *buy* an actual pedal sprocket with a freewheel in the middle!
I popped off the R/H chain fairing.  It makes it much clearer how the thing works...

I also removed the R/H crank arm.

Web searching shows that it's not totally unknown to see a freewheel on the crank.  Shimano used to do them ( the FFS - Front Freewheel System ).  Also,
they seem to be used on mountain bikes.  AND on center-drive ebikes.

There is a little plastic sprocket contacting the pedal chain.  It's attached to a little electrical thing with some wires going out.  I imagine it's a strain gauge, and
that's how the auto pedal assist system worked.
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I ordered a front freewheel, pedal arms and chainwheel from So with any luck, I'll be riding in style by the weekend. Front freewheels are apparently not uncommon on mountain bikes.
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OK, the front freewheel is installed. One complication was that sickbikeparts offers 30-tooth sprockets and 36 tooth sprockets...and the existing sprocket is 33 teeth. I chose 30 teeth because I'm old and weak, and need all the help I can get to make it up the hill Smile. Of course, the chain got all loose and I had to remove a few links. Then the chain for the motor got loose. I was starting to research parts for the (tiny, nonstandard ) chain when I realized that the whole motor assembly was on a pivot with an adjustment screw. A couple of turns on that adjuster got the motor chain tight again.

The bike rides MUCH better with that front freewheel. I can actually get on it, hit the throttle, and go. Almost like a motorcycle.


It's not very strong. Not strong enough to get me up the hill without pedaling. And the bottom gear is VERY low with that 30T front sprocket. To comfortably pedal, I need at least second gear, which puts the motor at even more of a disadvantage. So I have some troubleshooting to do.

First thing is better battery connectors. I used the cheap connectors that came with the controller, and they're quite warm after a short ride. I obtained a baggie of AMASS
XT60's, which should be better.

Then - what about the controller? I used a "Wingsmoto 24v 500w Motor Speed Controller Electrical Scooter E Bike Bicycle Tricycle Brush Motor Control Box " from Amazon.

Lastly, the battery itself. It's a 7s5p that I made of Pegatron modem cells from batteryhookup. Just a hair over 10 amp-hour capacity per the repackr tool. I put it together with substantial nickel straps spot-welded with the kweld. HOWEVER - the individual cells are rated only 2A per cell. So that's 10A total. 10A at 28V is 280W maximum. I have a 20A BMS on it.

I think I need to instrument it. Strap a meter to the handlebar, ride up the hill and see what voltage and current is produced. I have a no-contact DC current probe rated 0-60A. Not super accurate, because readings will change when the bike turns in the earth's magnetic field - but close enough for govt work. Or, if I want to get real answers, instead of a meter, I should strap up a battery powered digital oscilloscope ( yes, I have one ). Hook one input to the motor voltage, another one to the current probe. Then I'll be able to see the PWM pulses driving the motor, both as voltage and current.

Another thing to try would be to just hook the battery directly to the motor - with a switch - and see if it makes more power. If so, the controller is a weak spot.

If it turns out that the battery is not adequate, I might bite the bullet and buy a set of brand new high-current cells - Samsung or LG - 3600mA-h, and put together a pack with the 40A BMS I've got sitting on the desk here.
OK - I upgraded the battery connectors to the Amass XT60. I think it made a difference. Still not too strong though. I strapped a multimeter to the handlebar with masking tape, connected a current probe to one of the motor leads. Rode up a slight incline, I was seeing currents between 28A and 50A.

On this very short test ride, the battery got seriously warm.

Just ordered 36 new LG MJ1 18650 cells from batteryjunction. These are rated 3500mA-h and 10A continuous output. I shall make them into a 7s5p pack ( got one extra cell just in case ) and package it with a 40A BMS. I suspect that the internal resistance of the existing pack is choking down the motor.

...and going back to the basics, I cleaned and lubed the chains; checked the tires, they were way low. Performance is a bit better, but still no cigar. I want it to carry
me up the hill at 10-15 mph without pedaling. Is that unreasonable?

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