I think I'm a big sissy, but.....

[iangreenhalgh]

Finally finished my first ebike build today.

Put a pair of '1000w' Chinese hub motors on my old Kona MTB and built a pair of 48v 20Ah 18650 packs for it.

It's just too powerful, this thing isn't an electrically assisted bicycle, it's an electron fuelled rocketship.

The tires and lightweight frame just feel like they can't handle the power and I don't like the way even modest throttle application has me shooting along faster than is worth pedalling.

I built this thing to get more exercise and I think it's complete overkill, I'm almost never gong to need to pedal.

So do I sell it as-is and build a new less powerful one or do I rebuild this one with one motor and perhaps a controller that draws less amps?

 

[Antenor]

Maybe detune is the easiest way.
Only one motor and 20 amp will be enough to make it fell like a bike again.
And you can always use the other motor to do a street bike

Enviado do meu SM-G850F através de Tapatalk

 

[dustNbone]

It sounds like you might need to reprogram your controller for more reasonable throttle response, or replace it with one that will allow it. Maybe something that will give you a 3 speed switch for different power settings on the fly. You should be able to tame it down to make it easier to control, but I'm not knowledgeable on your controller/motor at all so hopefully someone else here can give you an idea.

 

[nutnspecial]

As above, so below. Well, right here, for now, as bottom post = tame the controls (or get used to it , adding appropriate pedal gearing.), or take one hub off and reuse/resell and/or drop your amps down by modding the shunts.

1x 1000w is like 4 humans pedalling madly, so what in the world gave you the impression for the first build that 2wd (2kw) would somehow just be 'assist' lol? Sure it can be, but for most users it's like 'assist' potential of 5-10x full human power!

electron fuelled rocketship

Lol welcome to our club!!!

 

[iangreenhalgh]

Well, let me explain that when I started building the thing a little over 7 months ago I was 100lbs heavier and felt I would need two motors to get me up the big long hills here.

However, my health has improved drastically allowing me to lose weight, so clearly now, I don't need two motors.

There are other problems than just raw power however, I mounted the batteries in panniers either side of the back wheel and the weight distribution is all wrong, I took a corner fairly slowly and the damn thing went sideways and I smacked sideways into a 1000 litre builder's bag of sand, lucky that was there or it would have been the stone wall behind it.

I'm sure 3000w is a lot of fun on the right bike with the right tires, but not on this bike, sadly, it's just dangerous. I say 3000w because my watt meters show the controllers pulling a tad over 30A, despite there being marked 28A and my 13s batteries are over 50v fully charged so the Chinese are rather under-rating their '1000w' kits.

I'm kinda broke right now so I'll take the option of rebuilding this bike with just the rear motor and mounting one of the batteries inside the triangle of the frame.

I'll keep the other motor and battery and parts though, when money allows I'll rethink my bike strategy again. Might go for a fat bike.

 

[nutnspecial]

Lol, yep better too much power than not enough imo! My neighbor is planning a 'fat boy' (That's wat he calls 'em, still after being corrected 3 times lol- I don't know how much hope there is for that potential ES'er :x ). But fatbikes def have their niche/potential- I wouldn't mind trying one prob for under 20-ish mph and offroad, with as much power I can get, that the tires can take .

I'm curious what gross vehicle weight is for you now, with 2kw being high overkill for assist? And what type of gradient? I noticed a single 1kw DD needs human assist on the steeper stuff (+10%), with ~225lbs GVR.

I guess it comes down to whether you're assisting it, or it's assisting you?

 

[iangreenhalgh]

Now , I weigh 320, but I aim to get that down to 270.

I think a lot of the problem I'm having is using a cheap crappy bike with cheap, crappy tires - too much power for the platform.

The other problem is how I mounted the batteries, it's so tail happy it makes a Porsche 9-11 look well planted!



It's not so bad in a straight line, but corners it does not like.

Gradients, well, I live in the Cumbrian mountains so it's not so much the steepness (although we have plenty of steep) it's the duration - I fear burning out a motor as some of the hills are very long climbs.

 

[Alan B]

If you could get that battery weight into the triangle things would work out a lot better. Perhaps put a switch to turn off the front motor when you don't need the power.

 

[iangreenhalgh]

I'm working on rebuilding the batteries into one that will fit into the triangle. I think the largest I can manage is 13s 12p, and given that I'm using Samsung 26F cells, which have a 2C discharge rate, I don't think 12p is enough to handle both motors as the controllers pull 30A apiece and 12 x 5.4 = 64.8, so it will just about do it in a pinch, but I keep reading that it is best not to go above 1C and preferably not above 0.5C with laptop grade cells.

 

[Alan B]

If your controllers aren't programmable you have a number of choices, from adding a Cycle Analyst or two to getting better controllers.

Part of your problem is the poor throttle control of those controllers you have. If they were torque mode you could modulate the power finely and avoid the overcurrent.

Depending on your budget and technical ability there is a wide range of improvement approaches.

 

[liveforphysics]

Part of your problem is the poor throttle control of those controllers you have. If they were torque mode you could modulate the power finely and avoid the overcurrent.

Alan nailed it. It's not over-power, it's under-control-of-power.

Get FOC motor controllers.

 

[whereswally606]

I have some Lebowski pcb boards coming in from china, pm me if you want to build one, they are a pretty good foc controller once you have built it.

 

[iangreenhalgh]

This FOC thing sounds interesting, where can I read more on it and these lebowski boards?

Worked on the bike all day so far and stripped off all the wiring, removed the panniers and the front motor, now to start rebuilding it.

Already started on the battery, it's as big as I can make it and still fit in the frame - 13s12p using 156 Samsung 26F cells. I need to get some 5mm MDF or plywood and make a box to put it in now.

 

[Alan B]

http://www.copleycontrols.com/Motion/pdf/Field-Oriented-Control.pdf Paper describing Field Oriented Control

https://endless-sphere.com/forums/viewtopic.php?f=31&t=65031 for the PhaseRunner Field Oriented Controller, one example of a new commercial controller optimized for bicycles, from Ebikes.ca

search for threads by lebowski, many threads on that project