Have a plan for adding a second motor I need vetted please. I a newbie.

[Adamshmadam]

My bike: 2017 ancheer folding. Sport. Moutain
55 pounds. The words sport and Electric vehicle are printed on it.
26 inch 1.95 tires.

Existing motor: Bafang 8fun rear hub cassete
Labeled 250 watts 36 volts. Geared. Gear ratio 1:4.2 I think.


Plan: Buy a front wheel with the motor and disc and tire already attached. That will fit the measurements of my front fork. I'm trying to find this exact motor built into a front wheel.

The original control box has been removed I plan on buying two identical control boxes hooking up those identical control boxes to 2 identical motors. And hook up one battery to both controlers. Hook both controllers to a remote shunt which is attached to a cycle analyst 3. Then hook up throttle to the cycle analyst.

Instead of 36 volts I'm going to use 52. But use the cycle analyst to limit the total amperage to Under 20. Total Peak output of 1,040 watts. So I can get more RPMs more power without a lot more Watts. Don't plan on opening up the throttle all the way just keeping it at like seventy-five 80% if i have to.


Wouldn't mind getting something a lot cheaper than a cycle analyst that would accomplish the same thing.

No pedal assist

Pretty much what the dude at ebike school told me to do after watching this video about 8 or 12 times I kind of have it mapped out in my mind.

So there's probably a lot of details I'm missing some things I am sure I got wrong so if anybody can help vet my plan and help me not make some serious mistake I truly would appreciate it.

CHEERS,
Adam from saint louis

 

[flat tire]

2 motors is sub optimal for an ebike. Ditto front motors. A single higher performance motor is nearly always better.

In general I recommend rear direct drive hub motors. Smooth silent and powerful motors are cheap and come with nice sinewave controllers. The big question is, are you racing off road or riding up big / long hills? I take it not too many hills in stl.

Cycle analyst is worth having whatever you do.

 

[Skorohod]

CHEERS,
Adam from saint louis

Hi, Adam! Make sure your both motors would have same kV with same wheel outer diameter (they should be equal or as close as possible at least), it's crucial for efficiency. Don't forget to reinforce dropouts of your front fork (even small motor can cause a mess with it's torque).

As for controllers and screens, check out for KT controllers with KT-LCD screens. You will need two screens to gain full control of two controllers, but is still can be cheaper, than one CA. Some people use one KT-LCD screen with two controllers with connection through switch or relay. As for alternatives, two 6F Nucular controllers would be perfect, they share one screen through CAN bus, all controls wiring from your handlebar goes only to screen (that eliminates mess with wiring).

 

[markz]

Why are you bothering with 2 motors?
Better to have one more powerful rear hub motor!

.

 

[Adamshmadam]

I think that sounds like a good idea. I don't want to do any mechanical work cuz I suck at it. I want to Simply screw on a new wheel and torque arms. Or pay someone to.
Any suggestions of what would be a good motor direct preferably because on the flats I will save a lot of juice . But it is hilly here and I need a beast of a direct that also get me up the hills. Thank you my friend for your feedback in any more advice you can give me particularly a complete wheel Tire buying suggestion. Thanks it sounds like a lot less complicated plan.

 

[markz]

MXUS 3000W, rear hub, 4 or 5 Turn Count motor in a 24" bicycle rim. Alex DM24 rim, Sapim spokes. Greentime controller.

Next is your battery choice, lots to choose from out there. You say 52V, but 48V is good too. Dont forget a charger, and having enough capacity (Ah) for the distance you want, and discharge (A).

Torque Arms can just be a flat piece of steel, using an angle grinder for the slot where the axle slips in tightly. Then hose clamps to fasten it.

Buy a spare throttle.

Dont need a Cycle Analyst, makes your bike stick out when its locked up.

 

[AngryBob]

What is it you are trying to achieve? More speed, range, hill-climbing?

Current plan seems unwise, though doable.

That thing about not using full throttle, well, that just never happens.

The big DD rear hub is a good choice in many situations, weight and unpowered drag are the drawbacks.

Simply making the battery upgrade with existing hub may work for you, with some care taken to avoid overheating. You would likely need a new controller.

 

[Alan B]

Welcome to ES, Adam.

It is good to think in terms of what your specific goals are and state them clearly. More RPMs and more power is a bit vague but a good start.

I have approached this "insufficient power" problem in different ways on different bikes. I have done both the "different motor" and the "dual motor" solutions. You can see some of those threads in my signature. Adding a second motor doubles the performance in terms of power, which is an amazing step up. Doing the same in one motor in the rear requires a motor which is twice the torque and power. This large motor brings a lot of problems - for example twice the magnet width is one way to double the torque capability (at the same diameter) and there may not be room for that, and even a modest increase in torque capability may not leave room for much gearing anymore. Adding a front motor leaves the rear motor and gearing alone. The dual motor beats most single rear wheel bicycle motor upgrades for acceleration, traction and low speed thrust. It preserves the rear wheel, gearing and motor which may otherwise clutter your garage. But it is not an easy path to take.

First off, going from 36V to 52 volts makes a big difference just by itself. With increased power you can overheat the motor, but if you are careful and set the proper limits in the controller and display you can get a lot more out of it without damage. A motor temperature sensor is important. For a geared hub 52 volts is a good choice. Higher voltages can be very hard on gearmotors. Perhaps you should plan for dual motors but execute the 52 volt upgrade first and then re-evaluate if more is needed.

Adding a front motor makes a HUGE improvement in power. But it also adds weight and complexity. Suspension front forks can be challenging to put a hubmotor into, and the motor's torque on the forks may cause them to bind and not slide very well.

There are lots more wires on a 2WD bike. Managing wires on a folding bike is important.

One throttle and one battery is fine, though the battery needs to have double current capacity to handle dual controllers. 20 amps divided between two controllers is pretty limiting, more capacity would be good, even if you don't use it often. The two controllers should be physically very close together and the negative battery leads connected together very close to the controllers as any voltage differential between the negative leads will cause the throttles to be interpreted differently and the voltage drops from the current in the negative lead can make the interactions worse. You'll want physically small controllers. The Phaserunners would be optimal but costly, you may want to try cheaper solutions but they may be problematic.

The Cycle Analyst is pretty much unmatched for programming and control capabilities. You could always make your own with an Arduino or similar but it is a lot of work.

The Kv (rpm per volt) of the motors should be close to the same. Front motors are not as wide as rear motors, and motors come in many different windings so getting the exact same motor for the front may not be practical or possible. If you use a controller that has torque throttle it matters a lot less as the torque mode equalizes the speeds and keeps both motors working together. Speed mode controllers are much more problematic and not recommended for dual motor single throttle setups. One or the other motor will do most of the work with speed mode controllers, and they can "fight" each other. Identical Kv's don't totally solve this, but torque mode controllers do.

Your bike is very light (for an ebike). The weight is going to go up with pretty much every one of these changes. A more powerful rear motor, a bigger battery, dual motors. In particular DD motors which can take a lot more power, are heavy. More powerful geared motors aren't as heavy and generate more torque at low speeds but require more maintenance. If you are going to put much power through geared motors get spare gears and clutches, and put better grease in them.

You will need torque arms on both motors. These become more important as the torque is increased. They make it more difficult to fix flat tires.

Good luck on your journey.

 

[flat tire]

Adding a front motor for hard acceleration defeats the purpose. If you get to where you can even smell power, let alone taste it, your front wheel will be barely skimming off the ground every time your bike accelerates.

Also this guy wants to go from a 250W geared hub motor to something better so none of the stuff about a single motor being too big applies.

A 9C or 1500W leaf would blow this guy's mind.

 

[john61ct]

Adding a front motor for hard acceleration defeats the purpose. If you get to where you can even smell power, let alone taste it, your front wheel will be barely skimming off the ground every time your bike accelerates.

Are you talking about where weight distribution is greater over the back wheel?

Putting 40-75lbs towards the front should help with that right?

Or irrelevant with an extra-long cargo or tandem bik right?

 

[flat tire]

Yes, front hub is good place for anti wheelies but with double digit KW on a fat hub with any kind of normal bike wheelbase you will still lift the front into 30+ mph depending on body position.

A dual motor bike could be cool for a top speed run or something like that. But it will suck for everything else, except maybe exceptional situations like deep mud or swamp.

 

[john61ct]

Pushing very heavy loads up long steep hills.

 

[Alan B]

It depends at what power and performance level you are working in. Clearly if you put enough power into the back wheel the front won't have useful traction. This would be "drag racing" level performance. I experienced that at about 6000 watts to a rear Cromotor. I've never experienced that with 1500W or even 2500W to a 9C. At least not on a mountain bike frame. I've put 2400W to a rear 9C and 1200W to a front BMC gearmotor and it works extremely well, outperforming a fat tire bike with a Cromotor in some testing we did. It has zero tendency to wheelie as far as I've seen. Believe me the gearmotor is adding a LOT of torque to this bike, turning it off is really noticeable. The gearmotor is really good at making torque at low speed. In my case I wanted to preserve a good rear 9C motor wheel but needed more thrust at low speeds. The 9C was not operating efficiently at these low speeds (climbing steep dirt). Adding a front motor totally solved the problem. Both motors are cold running at low to moderates speeds up steep dirt fire roads. It completely altered the character of the bike.

The original poster, in this thread seems to be looking for around 1kw total power performance, without throwing away his gearing or his rear motor wheel. Clearly at these modest power levels a front wheel motor is effective. Changing to a 9C or Leaf motor in the rear comes with a lot of negative issues like increased weight, poor weight distribution, loss of space for gearing, etc. Not everyone wants a bike like that.

Have you run dual small gearmotors in an ebike? Some direct experience with that type of configuration would be useful to this thread. There are people who have done this and threads talking about this on ES.

The OP stated that he's in hilly country, so any DD solution is going to have to be compared against the hills to determine the suitability. 1000 watts to a DD motor is not very good at climbing hills. If the power budget is increased this can be solved. 1500W helps a lot. 2500 watts is better. 4000 watts is really nice, if you have the motor to handle it.

 

[Adamshmadam]

Interesting you should ask. It's purely because of the steep grades here in my village of Glen Carbon, Illinois in the Saint Louis eastern metropolitan area. 25 Minutes from downtown. It is very hilly here. I like on top of a glen. All down hill or all up for a ways on some steep grades.

Thanks for the feedback
CHEERS,
Adam