Best motor setting for cargo bike

cwah · May 30, 2018

Hello

Here is my full suspension cargo bike:
https://www.dropbox.com/s/fj7f2z9jrhf2q3t/IMG_20180521_010859.jpg?dl=0

- It is used on big city with lots of start and stop.
- It will have load between 100kg (just me) and 250kg (me + passengers and cargo)
- It will need sometime to accelerate quickly to escape from dangerous situation
-Only need 15-30mph speed. Average probably around 20-23mph.
- It's raining a lot and I do about 600 miles / month. Mid drives are probably out of equation because due to the amount of miles I'd probably have to service the motor/chain/cassette every few weeks and that will drive me crazy

Currently I have a leaf motor 1000w and use about 60v 50A. So 3000W peak.

However, it's not that efficient and struggle a bit uphill and acceleration.

What best configuration for my need?
1. Add a front geared motor. But which one? I consider maybe the q128h at 1100W (55v20A) but I'm concerned on broken clutch
2. Get a bigger rear motor like the mxus 3000

danielrlee · May 30, 2018

cwah said:
Hello

Here is my full suspension cargo bike:
https://www.dropbox.com/s/fj7f2z9jrhf2q3t/IMG_20180521_010859.jpg?dl=0

- It is used on big city with lots of start and stop.
- It will have load between 100kg (just me) and 250kg (me + passengers and cargo)
- It will need sometime to accelerate quickly to escape from dangerous situation
-Only need 15-30mph speed. Average probably around 20-23mph.
- It's raining a lot and I do about 600 miles / month. Mid drives are probably out of equation because due to the amount of miles I'd probably have to service the motor/chain/cassette every few weeks and that will drive me crazy

Currently I have a leaf motor 1000w and use about 60v 50A. So 3000W peak.

However, it's not that efficient and struggle a bit uphill and acceleration.

What best configuration for my need?
1. Add a front geared motor. But which one? I consider maybe the q128h at 1100W (55v20A) but I'm concerned on broken clutch
2. Get a bigger rear motor like the mxus 3000

Cwah, how long have you been reading these forums? Surely you of all people have learnt by now the KISS principle?

Keep
It
Simple
Stupid

A single large DD hub motor is what you need, but I bet you already know that deep down, don't you? I'd look at the MXUS 3k & QS205 with the possible addition of ferrofluid.

What is the spec of your battery pack for this bike? I suspect this might be where the key to your current underwhelming performance lies.

Also, are you maxed out on your controller current, or is there any headroom available to reprogram?

cwah · May 30, 2018

My controller can do up to 350A. It's enormous.

My battery can probably do 80A at 60v

But my motor is rated 1000w and phase wires will melt.

I could get a bigger motor but I m not sure it would be as efficient as getting a 2nd front geared one

danielrlee · May 30, 2018

cwah said:
My controller can do up to 350A. It's enormous.

You could always try temporarily reprogramming a higher current to see how the motor responds. If you don't get the performance increase you expect, it might suggest a battery issue.

cwah said:
My battery can probably do 80A at 60v

What's the voltage sag of the battery while drawing 50A as you currently do?

cwah said:
But my motor is rated 1000w and phase wires will melt.

I'm currently running 3.5kW through a H3540 (1000W rated) and the 12AWG phase wires cope fine. If yours get hot at the connectors, they're likely the issue. Although it won't save you from burnt phase wires, do you have temperature monitoring on your motor? Thought of adding ferrofluid?

cwah said:
I could get a bigger motor but I m not sure it would be as efficient as getting a 2nd front geared one

Your DD Leaf mounted in a 20 inch wheel is probably more efficient than you think.

dogman dan · May 30, 2018

Well, its not really all that inefficient, its just really loaded. Anything over 200kg for bikes is reallllllllllllllly loaded.

Uh,, kind of like when you fill a pickup truck with rocks, it sure does take off from a light slower. Plenty of power, and efficiency, but 3000 pounds of rocks will slow ya down.

I would say throw 2000w at least at it, a motor rated for 1000w should be able to take 4000w intermittently. But limiting to 2000, maybe 2500w means your phase wires don't have to be gargantuan. Splice on fat wire soon as you can though, so the thin wire inside can heat sink out to fat wire soon as it gets out of the hub.

This is all shit you know by now of course. Just posting to confirm what you know.

cwah · May 30, 2018

I can just increase the throttle input and it would just increase power on my controller.

I just tried to pull 100A and my battery voltage went down from 59v to 50v. I think at 50A it goes down to 55V from 59v. So it's a bit saggy but it's ok.

I don't have temp monitoring on my motor but I know the phase wire will melt before because a bit of them have already melted so I'm considering changing motor. The wires come out from the end of the axle and it makes it super hard to replace.

I can obviously get a much bigger motor, but the question is... Would that be more efficiency than a small geared drive on the front? The constant start and stop + heavy load are really the main issues . Direct drive really don't thrive for low speed and high torque.

If adding a geared allow me to accelerate decently and increase significantly the range it would be maybe greater? I'm trying to simulate with the simulator but I'm not sure how best to compare dual drive Vs single on constant start and stop environment

danielrlee · May 31, 2018

cwah said:
I can just increase the throttle input and it would just increase power on my controller.

I just tried to pull 100A and my battery voltage went down from 59v to 50v. I think at 50A it goes down to 55V from 59v. So it's a bit saggy but it's ok.

I don't have temp monitoring on my motor but I know the phase wire will melt before because a bit of them have already melted so I'm considering changing motor. The wires come out from the end of the axle and it makes it super hard to replace.

I can obviously get a much bigger motor, but the question is... Would that be more efficiency than a small geared drive on the front? The constant start and stop + heavy load are really the main issues . Direct drive really don't thrive for low speed and high torque.

If adding a geared allow me to accelerate decently and increase significantly the range it would be maybe greater? I'm trying to simulate with the simulator but I'm not sure how best to compare dual drive Vs single on constant start and stop environment

Although less than ideal, the voltage sag seems reasonable for the battery, so I agree it is not the issue.

I disagree that a DD hub motor in a 20" wheel is inefficient, though it's all relative.

If you increase the current to your existing motor, or add an additional geared motor, you're still going to be limited to roughly an additional 1kW, so you won't see huge performance gains in either instance. In addition, 2WD will require another controller, so creates additional complexity. Admittedly, it would give a little redundancy if one of your motors/controllers were to fail.

Upgrade your existing motor to a larger DD hub and with more current there's no reason you won't see near enough 100% performance gain. Managing the torque will be its own issue though.

cwah · May 31, 2018

Yeah it's all relative.

But for condition like mine, how can a bigger DD be more efficient than a low rpm geared motor?

Imagine a scenario where I need to do a 15% grade with 250kg load. My small geared low rpm could be running close to peak efficiency at 5-10km/h. It would also help on start & stop situation.

Of course, these are just hypothesis. I'd need a real life situation to compare

danielrlee · May 31, 2018

It might sound a silly question, but why do you seek to improve efficiency? Why is your bike not efficient enough as it stands?

Surely the real issue is the lack of power. In that regard, how much gain do you expect from a small geared hub motor when you're already running 3kW?

cwah · May 31, 2018

I was thinking as I do a lot of start and stop with heavy load, most of the time the motor is running on its inefficient band.

More power = even more energy wasted.

The hope was to increase range by 20% by adding a more efficient geared motor

markz · May 31, 2018

Geared Efficiency only in regards to the stop and go.
Then there is the noise the geared motor makes.
Also there are more moving parts in a geared motor.
Then what if teeth start breaking off, I bought a BMC V1 with one gear 1/4 stripped. Not sure how that even happens.
Yeah go with a MAC motor from EM3EV and find the right turn count you require with what controller and wheels you have.

You could have a torque monster with an ultra silent direct drive MXUS 5000W in a 21" wheel, say a 3T or 4T where it can just take the amps, then match with a Sinewave Controller. That would be an absolute beast of a machine!

dogman dan · Jun 2, 2018

I think you are just wanting to start fast on not much battery, spike loads, or resulting sag. You want a fast, efficient start.

Well buddy, it aint happening more than you have already. You are there at max efficient setup for hubbies, with a pretty big motor and 20" wheel. The only real way to get that fast start more efficient is to lose weight.

Your battery problem is just that you throw too much amps at it, a slower start, using about 2000w is going to be more efficient.

Fast starts in traffic ARE great. But to get them use this.

cwah · Jun 2, 2018

Hey guys

You are probably right. I should just get a bigger motor. I m thinking to put a mxus V3 turbo with bent magnet. Hopefully weight shouldn't be too high

Best motor setting for cargo bike

cwah

100 MW

danielrlee

10 kW

cwah

100 MW

danielrlee

10 kW

dogman dan

1 PW

cwah

100 MW

danielrlee

10 kW

cwah

100 MW

danielrlee

10 kW

cwah

100 MW

markz

100 TW

dogman dan

1 PW

cwah

100 MW

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