My new fat e-bike disappoints - how can I get more power!

[savski]

Hi all,

I wonder if anybody out there can help me. I recently bought a fat e-bike (spec below) with the dream of cycling to work off-road in all weather conditions (I'm in Switzerland where we have a lot of snow!). Anyway, there's a big hill and a couple of smaller ones between me and my work place (15km total distance/550 meters total elevation gain) and needless to say my 26kg fat bike only just about limps up there and I even have to get off and push sometimes, I would probably be quicker on a light-weight mountain bike to be honest but let's not go there!

So the bike has a Bafang hub motor, not sure if it's a 350w motor that's been restricted to meet European laws or if it's really a 250w motor – I tried asking the company but they never reply whatever I ask them and only email contact is given so I can't even phone them.

https://www.surface604.com/fatbike/boar/

So anyway, has anybody got any advice for me? Can I just go and buy a bigger Bafang hub motor and replace it with my existing one – or should I look into getting an additional motor for the front wheel, not sure of any other options. Any help greatly received!

 

[fredfire]

EU laws make it very hard for you to get decent power from a vendor ebike. You'll be better off by building it yourself.
You could try to return the bike (if it's new).
If not, the problem is that the bike has a 36v battery, a easy diy motor would be a bbs-hd and it require a 48v battery.

 

[Zeusless]

I would return the bike. Because already the vendor showed you they are not interested, then when the bike has more problems you will be out of luck. Plus, the bike doesn't perform to how you need anyway.

 

[Drunkskunk]

It depends on what you want from the bike, and what it will take for the bike to not be disappointing any more.

250w on an ebike is good for pulling someone along at pedal bike speeds on reasonably flat ground along smooth trails or paved roads. And that's about it.

With some serious work, you might be able to double the power of the bike and totally void any warranty it had, but that would be about it, and double the power on that bike would still leave many thinking it was a disappointment.

The fun starts at about 4 times the power that bike has. a hub motor of 1000 watts would just start to be capable of off road fun.

 

[Esting]

The battery and controller is built into the frame of this bike it will be very difficult to replace for something bigger say 48V and for more power you need this.
I have taken a test ride on this bike and this was a 350W Canadian version , yours will be a 250W, I quickly realised it was not what I wanted.
And ended up with 48V -500W (850w Peak) (VoltBike Yukon) which I can upgrade Battery/Controller and Motor if I see fit down the road , or when the parts need replacing . I am sorry I now this not going to help you.
This is a link to my bike.

http://www.voltbike.ca/voltbike-yukon/voltbike-yukon-500w.html

 

[motomech]

Install another complete 350 Watt system on the frt. wheel for 2WD.

 

[Eskimo]

EU laws make it very hard for you to get decent power from a vendor ebike. You'll be better off by building it yourself.
You could try to return the bike (if it's new).
If not, the problem is that the bike has a 36v battery, a easy diy motor would be a bbs-hd and it require a 48v battery.

Just wondering, how EU-laws can make it hard for him because his country is not part of the EU...

Switzerland (not in EU) has led the way on speed e-bikes in Europe, liberalizing standards and allowing for an easier process of obtaining a license to use 45 km/h ebikes as an alternative to the common 25 km/h pedelecs found in the EU.

There might still be that stupid 250W-limit in place, but it"s not because of the EU.
If you buy 250W bike, you get 250W bike. It"s sad really, 250W is weak for heavier riders and frames.
Overvolt it? 48V?

 

[LewTwo]

I can run a 250 watt 36 volt rig with no problem
... but I only weigh 150 pounds, the bike weighs less than 30 pounds and there is not a hill to be seen anywhere.

I would definitely send it back.
With that kind of money you can build something MUCH better.

 

[dogman dan]

When I rode the surface 604 at interbike usa, it definitely had a larger motor, and did not disappoint. I think you have a motor rated 500w, which can be run at double that wattage. I'm pretty sure I was riding at least 800w, maybe more.

Cant be sure, without a good picture of your motor. I think you just need to hack your controller, or change it, to get more power.

 

[Ykick]

Sometimes things can just NOT make much sense to modify and fuss with? I dunno if this is one of those or not but it’s something to ponder. At least the Bafang motor can probably handle a bit stronger controller?

But these factory built things are so often not worth going down the modification road. Sometimes Lemonade can be made but it’s often much time, work and expense to achieve a good eBike from a sum of various components.

Moral is: enjoy ‘em for what they are. And in this case that appears to not be much. Learn what you can, move on and continue with a better, more informed plan and eBike which actually satisfies.

 

[John in CR]

Savski,

Welcome to ES. Let's start with your load. The elevation gain is a 3.7% average grade, which is no simple task for 15km, but I'm guessing you have some much steeper stretches mixed in. I use a calculator to determine power requirements. Delete the power number and enter a speed to put it in calc the power mode. http://www.kreuzotter.de/english/espeed.htm.

You haven't mentioned your weight or how much pedal assist you're adding especially on the climb. Both will have a huge impact on what's possible with that bike. Unless you're using it as just electric assist, you're asking too much of the electric system. Exactly where it's falling short we don't have enough info to say. To start with I don't think you have enough battery, not for a long climb of a commute. Sure the bike would do 30km or more on flat ground, but just like pedaling a bike on level ground is leisurely and easy, it's simple for the motor. You're asking for long periods of maximum power from the system.

Let's look at what happens during the climb. Battery voltage decreases with status of charge, so you have less power on tap at the end of the ride than at the beginning. As the status of charge goes down, the amount of voltage sag under load goes up for even less power on tap at the end. Every part of the system has resistance, and current flowing through any resistance make heat, so the batteries warm up, the wires warm up, but most of all the motor heats up. As the temperature increases resistance increases making more heat and creating more voltage sag for even less power on tap. As you bog down to a crawl it sends max current through the system, but since power is equal to torque X rpm, you're getting very little power out, and the resulting very low efficiency means the battery energy is being turned into heat not work.

Geared hubmotors like you're little Bafang have difficulty shedding heat, because the motor itself is inside and other than via the axle it has a layer of air insulating it from the outside shell. Avoid riding to bogged down conditions at all cost, because you risk thermal damage or failure.

The first thing you need is to get a Cycle Analyst, so you can find out exactly what's going on with your bike in terms of voltage and current usage, and how your battery is responding. It may be that the controller is being too restrictive or has some Euro market power restriction, but a new controller is unlikely to solve the whole problem unless you're adding lots of human effort.

Adding a motor to the front is sure to make a tremendous difference. Not only do you double the power and heat dissipation, but each motor sees only half the load your current motor sees. Front hubmotors have special considerations and absolutely require proper torque arms to lock the motor axle to the fork and spread the thousands of pounds of force of the axle acting on the dropouts at such a small radius out to a further distance from center to lessen the force.

One thing to consider now is brake maintenance. For every uphill there's a down, so you'll be fiddling with brakes a lot. The only exception is a direct drive hubmotor, which can give you regen braking. Not only does it add some juice back to the battery, but the real payoff is drastically reduced brake maintenance, since it handles most of the braking work. There's also an increase in safety, because it keeps the brakes nice and cool and ready for emergency stopping. If you're interested in switching to direct drive then now is the time.

You've got a good foundation for a great ebike, so don't give up now.