up-rate suggestion for hill climbing

D

davechiu

1 mW
Joined
Jun 8, 2009
Messages
16
Dear all,

I have this bike:
220081022162838.jpg
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
 
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. :D
 
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 said:
davechiu said:
My question are: Can a stronger motor help? if so, how much power is required?
Click to expand...

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).
Click to expand...

That is with pedaling? I suppose?
 
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.
 
davechiu said:
. But it seems to me going green isn't that easy.
Click to expand...

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 :p

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

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
 
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) :oops:

I am a ebike absolute beginner. I appreciate your kind comments and input.
 
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.
 
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.
 
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?ViewItem&item=300283998807&pt=LH_DefaultDomain_0&hash=item45ea523257&_trksid=p4634.c0.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.
 
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.
 
davechiu said:
Dear all,

I have this bike:
220081022162838.jpg
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
Click to expand...

You've got a lot of strikes against you with that bike

small motor that can't take a lot of power for very long

likely a low current controller which is matched to the small motor but means you can't generate sufficient power.

likely a low 'C' rated battery which is fine if the current load is low but may not function if called upon to deliver substantially higher currents. If the battery has a BMS it'll likely shut down if the controller current is increased too much.

large 700C tires are good for speed but they also mean a lower amount of thrust is available at low bike speeds such as when climbing a hill.

3-speed rear hub means you can't gear down and pedal comfortably at slow speeds.


I ride a conversion that's similar in principle with a 250W front motor in a 700C rim with a 15A controller. The steepest grade I've faced is about 12% and that was pushing the motor pretty hard and I run it on 48V. I'm not sure what the limit is for my combination but I'm sure it wouldn't do a 15 degree hill which is about a 27% grade :shock: With all that said I'd concur that the first step would be to try a higher current controller, maybe 25A, and see if your battery can take it without cutting out. If the battery fails to deliver the goods or the motor fails then it starts getting more expensive. the bottom line is to climb a grade like you say you have you need a more powerful motor, a high current controller and a battery capable of supplying high currents without a great deal of voltage sag.

-R
 
Lock said:
davechiu said:
Yes. Ebike is illegal in Hong Kong. That's why I am doing it.
Click to expand...
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
Click to expand...

Yes, that looks VERY similar to mine. But 1799 EUR? that's US$2600. Mine is just $600. Either the dealer marks up a lot, or they use some very high grade parts on it.
 
Let me start off by saying that I have only been e-biking about six months. But I also live in a hilly area and have the 48v 500 watt Fusin gearmotor kit. So I may be able to give you some answers.The guys on this forum know more than me.
One thing that puts this kit above others is the 3 speed switch. These "gears" aren't really gears. It's all in the amazing controller. Some how it electronically changes the torque range of the motor. I have found that virtually no hill can stop the motor when it's in low. Actually only one hill in my area can really stop it(a mile or more of +15% with a turn) and that's only when I tow my trailer(50+lbs.). It doesn't limit power it simply changes torque range. I know this because I have a cycle anylst that gives me amp and watt readings. From what I understand a gear motor is better for climbing hills anyways. Either way a hill like that puts alot of stress on the motor. I'm using Rassy's suggestion and building a pusher trailer. I carry alot of groceries. I've run mine till it burned my hand when I touched it. Plus you get a really cool headlight that would look good on your bike.
Two drawbacks to this kit. One it has a lot of wires. But with some zip ties and some creativity this is easily dealt with. Two is the Fusin battery. It has alot of voltage sag. The controller cuts out at 44v. Now even the slightest grade makes it reach cutout. If you switch down to a lower "gear" it stops but it gets old having to climb every hill in low "gear". Get a Ping battery. I've not had it cutout yet no matter what the hill. I posted this on the Fusin forum also except without the mention of the battery because I already talked to Louis about it. I just don't want anyone else to get a 325 dollar paper weight. I'm still getting 20 miles out of a charge so it produced as advertised but that's 20 miles in low or medium "gear". Anyways probably the controller idea someone had was the best. Good Luck
 
Yeah Dave, that is the controller I had in mind. If you are in HK, the shipping would be minimal so it would be a cheap upgrade. Ask that the PAS input be added, you don't have to use it. I'm not clear how yours works, but if you have a throttle, you can just not plug in the PAS connector on most controllers, including Kewin's. I did have one controller where it had to be plugged in, so I just moved the magnets away from the sensor. You will have to do some soldering and changing connectors. The only other thing to check is whether you can change the front sprocket to a smaller one if you need a lower gear for the hills.
 
Thank you Terry.

BTW, the eCrazyman hasn't replied my email inquiry on the shipping cost yet. Perhaps the S&H is a big part of the profit?
 
Dave I admire you for doing something that you know is illegal because the law seems unjust. Civil disobedience is the duty of any citizen anywhere when the law of the land seems unjust. If you don't stand for something you will fall for anything. Be careful but stand tall. Thank you
 
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