up-rate suggestion for hill climbing

[davechiu]

Dear all,

I have this bike: http://www.unikcycles.com/big_.asp?pid=155 It is a good looking and well built bike. Yet, its motor is too weak. I have a 15 degree slope to climb right in front of my house before I get to the main road. Right now it only has a 250W geared motor which isn't good enough.

My question are: Can a stronger motor help? if so, how much power is required?

I really don't want to waste this bike. Thank you very very much for your help.

David

[Rassy]

Hi David. Your comment about the 15 degree slope caught my eye as the road leading to my home has a 15 percent grade. Did you really mean 15 degree slope or is it a 15 percent grade? This makes quite a difference, since a 15 degree slope is over 30% grade.

Anyway, I thought I would share some of my experience with the hill I ride up, which wraps up with a 20% grade on my own driveway. Currently I have a Bafang in a 20" wheel on a recumbent bike. This is the Bafang recommended for a 26" wheel, so it has more torque and less speed in the 20" wheel. I run it with a 48V LiFePO4 battery. With moderate pedaling I can maintain about 9 MPH up the road, but it really starts to stall on my short driveway, but still makes it up with a few hard pedal strokes.

However, when I have my BOB trailer hooked up, which has the same Bafang motor in a 16" wheel, the whole rig goes up the hill (using both motors), at about 13 MPH with light pedaling, and doesn't slow down on the driveway.

So, here's my thoughts on possible solutions:

If your components can handle 48V you might try that.

You could go for a more powerful motor or an additional motor on the rear.

My favorite solution would be to leave the bike as is and add a one wheel pusher trailer with it's own throttle (on the left side). By being fully independent, the motor on the pusher trailer can be a different size motor in a different size wheel running at a different voltage than your bike. And if you use a geared free wheeling motor it won't have any noticable drag when you aren't using it.

Good luck with your modifications.

[davechiu]

Thank you Rassy for your response and analysis.

That slope, unfortunately, is a 12-15 degree slope. I have checked it (on an iPhone with inclinometer software). Imagine walking up that slope on a hot (95F) and humid (over 90%) summer day.

I really want to get rid of my car, or at least driving less, to cut down my carbon output. But it seems to me going green isn't that easy.

So in your opinion, if I want to keep modification to the minimum, a normal e-bike is unlikely to make it?

[Miles]

My question are: Can a stronger motor help? if so, how much power is required?

If it really is 15 degrees, you'll need a power of about 600 Watts to go up it at 5 mph (for 220lbs/100kg gross weight).

[davechiu]

My question are: Can a stronger motor help? if so, how much power is required?

If it really is 15 degrees, you'll need a power of about 600 Watts to go up it at 5 mph (for 220lbs/100kg gross weight).

That is with pedaling? I suppose?

[Miles]

No, that's the total power required. If you contribute 150 watts of pedal power, the motor needs to put out 450 watts etc.

Doubling the weight, or doubling the speed to 10 mph will, roughly, double the power requirement.

So, the minimum requirement would be a set-up with a motor capable of a 500 watt continuous output, when the bike is moving at 5 mph/8kph.

[AussieJester]

. But it seems to me going green isn't that easy.

Its not hard IMO but it definitely aint cheap thats the pisser ...

I think 600watt Miles mentions is WITHOUT pedal assist .EDIT: too quick for me Miles

I also live in a particular hilly area, my mate came up with his 1000watt non
hub motor cruiser last week, is the hill you speak of something like this
grade wise? Cylone make a 650W,720W,900W, 1200W, 1000W,
double 1000W bolt on kit that would suit your bike i think. Very easy
to instal too minimal tools required motor runs through bikes gearing giving you EXCELLENT hill climbing ability

KiM

[dogman]

That's a healthy steep hill! Is it very long? Chances are, your motor is not so different from a bafang, and one way to go at it, would be to try a 48v controller on it, and also upgrade to 48v battery. A 48v 20 amp controller would get you in the neighborhood of 900 watts, and get you up the hill, though you should pedal too. A real long 15 degree hill could melt the motor though. I find my fusin gearmotor overheats on 12 % hills in about 3 miles. Its a 350 watt motor system. Your old battery will die quickly if you try to put a bigger controller on it, so you'd need to spend on a bigger battery. I'm guessing you have 24v now?

But if that motor is too small, or the gears too weak, then the thing to do would be to throw money at it, and get the whole system new, and add it to the bike.
A bmc 600 watt, and some high discharge rate 48v battery should do the trick, or as suggested, a cyclone. Since your bike doesn't appear to have any gears, a cyclone would be a poor choice.

A less expensive similar solution would be a Fusin motor kit. They have a 48v gearmotor that should do it, but may not last quite as long as the BMC which is the better grade of gearmotor.

Another solution that would work for a time, get a bike rack and park the car at the bottom of the hill.

[AussieJester]

or as suggested, a cyclone. Since your bike doesn't appear to have any gears, a cyclone would be a poor choice.

Actually his bike has a 3 speed nexus hub (click the link in OP has bikes specs) same as the bike in the video i linked to using a cyclone kit going up and equally steep hill at 31km/hr. Even if it had no gears the option is there to re-gear it so a cylone has the ability to climb better than a hub motor on identical volts.

KiM

[davechiu]

Thank you! thank you! thank you all of you for your replies.

Dear KiM: That cyclone kit looks nice and the torque/power seems amazing. And it is cheap too. Sounds a viable option. Stealth factor is a concern though. No form of ebike is legal here...But if there is no other option, I may try the Cyclone.

Dear dogman: The 15 degree slope isn't very long, half a mile I think. But my home is surrounded by stretches of 1:10 to 1:8 slopes (some go up and some go down naturally). Do you think I should try a bigger controller first? The battery is a 36V 10Ah one. How much power, say, a 20A controller can give in this case? (What is the formula for the conversion? I think I should do the math myself)

I am a ebike absolute beginner. I appreciate your kind comments and input.

[davechiu]

The bike is actually quite a good one. I costs me less than US$600 with S&H and everything included. Just that I am asking too much of it. Not its fault.

I may take some photos of it to share with you before I take it apart for surgery.

[HTB_Terry]

Dave, the first step you can do is to ugrade the controller. You are most likely running at 15 amps, maybe 12A. You are probably running at about 350 usable watts. Going up hill you are going slow so the efficiency goes down, say it's only 250 watts. Increasing the current to 25 amps gets you maybe 25-35% more power. These are rough estimates but the bottom line is that you will get more power for the hills. Your range will decrease if you go up a lot of hills. The current protection on the battery might limit at 25A, but most don't. The next step would be to parallel a second battery to provide even more current. Then you could go to 30 to 35 amps. I would recommend the small 25A controller from Keywin. You do have to be carefull about putting a high powered motor on a suspension fork. That bike is not designed for hill climbing and does not lend itself to extensive rebuilding.

[davechiu]

Dear Terry,

I would expect something like this will work, right?

Ecrazyman 36V 350W brushless controller (25A max)
http://cgi.ebay.com.hk/ws/eBayISAPI.dll ... .m14.l1262

BTW, right now the bike has an 1:1 PAS which I find quite annoying. Can I get rid of that with a non-PAS controller? Is there any wire to cut? The thumb throttle is a normal '3 LEDs + a red switch' config.

[Lock]

Yes. Ebike is illegal in Hong Kong. That's why I am doing it.

Good Man

Yer Unikcycle "Dutch Lady" bike looks/sounds a lot like the "ave. Tour 26" Pedelec" bike reviewed recently by ExtraEnergy.org:
http://www.extraenergy.org/main.php?language=en&category=products&subcateg=119&id=2935

In their comments on the review:
"Power sensor needs to be re-calibrated often"

...just a thought
Cheers
Lock

[dogman]

Since the really steep slope is not so long, I'd try the higher amp controller, but if you went to 48v, then a new battery would be needed for sure. Maybe a 20 or 25 amp controller that can be run at either voltage would be a good choice. As long as the main power wires into the motor are not too thin the motor can take it. And if so, the wires could be made thicker to take more current. The only issue would be if the slope was long enough to melt a motor. A half mile won't be likely melt one. If you do stay at 36v, then Terry's advice to add another battery with a paralell connection makes sense. 36v 20 ah will power a 30 amp controller ok.

Nice bike if it has a nexus hub, no wonder you want to keep using it. I just thought it was a single speed since I saw no derailur in the pic.

A different controller would not require the pedelec, so it could be removed when the new controller goes on. You may be able to just unplug the pedelec wires on your current controller. Try it and see.