HELP: How increase max-speed of folding ebike 250W r-hub 36V

[segalion]

I have recently buy a fonding ebike with standar bafang 250W rear hub, with batery inside frame (sanyo 36V 10.4Ah distributed in 40 cells 10x4 with a 10s4p config)
This is a chinnese, cheap and fine design with tipical low cost but nice accesories (freewheel shimano megarange 7 speeds 14-34T, disk brakes, double suspensions, magnesium wheels, ...).

I can reach 30-31Km/h on flat with vewy low assisted, and I would like to increase top speed up to 35-40 Km/h and I dont know how to make it with minimun changes.
I have read that motor limit the speed by their RPMs, and I suppose its about 315RPMs.
I have read that best is to change to 48V, but its supposed very dificult for me. Do you know how increase the RPM overvolting?


The battery is a 10s4p inside frame so its very dificult to get 13s4p, and I dont know I I have to change controller or motor. Motor seems to support 48V, but I dont know nothing about controller.
I was thinking in get a 11S-4p (40V), but I dont know If I have to change (o re-program controller)

Do you know if there another options to get more max-speed with this configuration?

At first time I want to change the shimano 14-34T for a very difficult to find 11-32T 7 speed freewheel, but this only increase speed dowhill.

Thanks for the advices.

 

[ColinB]

To increase your speed, you could:
- Check that the maximum speed is not limited by to controller to be legal in your area.
- Increase power limit of controller. Controller may have power limit settings.
- Increase voltage. (New battery. Will also increase wattage, so may be too much for your controller and/or motor.)
- New motor with higher kv rating. (RPM / volt.) May draw more power, so may need new controller and/or battery.)
- Reduce drag. (Pump up tires, change to smoother tread tires, check that wheels spin freely, brakes are not rubbing, etc.)

35-40km/ha may be too much for a 250 watt motor. And, do you want to go 35-40km/hr on a folding bike?

Colin

 

[footloose]

I love small-wheel folders, but high speeds start to bring out their limitations.
I'm assuming this bike has 16" or 20" wheels?
Perhaps you should consider just riding the bike as is, but if you do want higher speeds...

The motor isn't the issue, it should run fine at higher voltages.
Battery and controller are the keys.

If battery is build into the frame, likely it is fairly proprietary config but you *might* be able to replace battery and BMS.
You've got a 10s4p battery, so 40 cells.
If you went to 13s3p, you'd have 39 cells, and battery could theoretically fit existing space but fitting a BMS might be difficult.
You'd increase voltage from 36V to 48V.
Use some high-end cells and you wouldn't necessarily have to give up any Ah capacity.
Replace the controller with a 48V controller and you'd be good to go.
But honestly, replacing the in-frame battery with a new custom-configured battery might be pretty challenging.

Alternate route: hang one of the small 52V ready made batteries from the seat (http://lunacycle.com/batteries/packs/52v/52v-mighty-mini-cube-ebike-battery-pack-panasonic-ga-7ah-3-pounds/ is an example) and get a new controller. You'd give up some battery capacty, but you'd gain top speed... probably max out around 40 km/h. I did that with a folder. The bike was fast, I think too fast for safety.

 

[Mündawg]

I recently just gave up on trying to do an e bike folder due to detremental danger at high speeds and with turning at those speeds. I was going very fast on my dahon down the mountain road, coasting, had to dodge a squirrel and the bike almost folded over on itself... Made me decide to turn my Trek Mountain bike electric instead.

but as others have expertly stated.. Keep the motor, change the battery and controller.. Or maybe even just the battery? Hear me out.. Put together a good 10S4P pack to fit, use high end cells and a top notch bms.. That way you can crank any controller settings and know the battery will deliver...
Other than that is speed is an issue step it up

 

[segalion]

Thanks to all for your recomendations.

The bike is 20" wheel with 2,125" tire width, and seems a fairly robust aluminium frame (able to support up to 125Kg weight).

I suppose that its not speed limited: in LCD display Im sure is not limited, and in controller I suppose its not limited too, because I get low assisted as I reach 30-32 Km/h (and no assist > @33Km/h). As I read that max RPM in hub motors are tipically upto 350, I have calculed this max speed limitation:
1. with my wheel perimeter = 1614.78mm ( 20inch BMX/Recumb 2.125 inch - 406 in http://www.bikecalc.com/wheel_size_math )
2. and If my motor could be 325 RPM máx (probably this is the motor specs. http://www.szbaf.com/en/components/component/motor/rm-g02250d.html )
I get that 325 x 60 x 1.61478 / 1000 = 31,48 Km/h, that is exactly the speed I feel as maximum, and over that, no assist is perveived...


I am surprised that all of you coincide in dangerous of a folding ebike with high speed ( more tha 30 Km/h).
I have only 250 Km experience, but I dont perceive danger (more than a standar bike). I am satisfied with torque on ebike, as It has little wheels.

All my trips are 10 Km to work, mainly street and very secure road (big streets) and my intention was to get more speed in some straight sections to gain some minutes, but as all of you recomend me not to increase top speed due to danger... I am going to follow your recomendations and forget to increase my top speed.