Leaf Bike electric conversion kit

[HagridsButtquack]

Hi everyone, I'm very new to electric motors/bikes so bear with me. I have an old 1970 Yamaha L5 that I'm wanting to convert to electric. It's a small lightweight 90cc bike so I shouldn't need a ton of power. I'm looking at getting one of the Leaf Bike conversion kits. I don't want to have to get a degree in electrical engineering in order to build the thing so a kit seems like an easy and simple solution. My main question is about brakes. The website is pretty vague on details, so I couldn't figure out how braking works. The bike currently has a rear drum brake, which will be removed for the new wheel. Do I need to add a disk brake? Do those motors have built in braking? The kit appears to come with two brake levers, presumably for rear and (front?) brakes. I will be leaving the front drum brake as is. Also, is there any reason to choose the 2000W over the 1500W? I will just be using it to cruise around the neighborhood, run errands, and using it more like an ebike than a motorcyle (riding in bike lanes rather than in traffic, etc). I'm also open to other suggestions as far as motors and such, but I want to keep it pretty simple which is why I like the kit idea. Thanks

 

[amberwolf]

Hi everyone, I'm very new to electric motors/bikes so bear with me. I have an old 1970 Yamaha L5 that I'm wanting to convert to electric. It's a small lightweight 90cc bike so I shouldn't need a ton of power.

To be certain it will do what you want, and so you can buy or build the right battery for it, you'll want to know how much power maximum, and continuously, that you'll need for it. I recommend defining the specific job you need the bike to do for you, under what specific riding conditions, and then you can use that info on simulators and calculators like the motor / trip simulators at ebikes. ca (using the custom fields) to guesstimate power needs, and also wh/mile power usage (to guesstimate battery capacity required for desired range).

If you're using this for typical motorcycle stuff, you'll probably need a much bigger kit than the one linked, with a bigger motor, etc--one designed for a motorcycle. But I can't say for certain without knowing the full details of your usage and conditions.


Once you have the kit you will also need a battery; you have to know what it has to support before buying one, since it is the heart of the system and must supply all the power needed to do everything you need the bike to do for you.

I'm looking at getting one of the Leaf Bike conversion kits.

If your dropout slots don't perfectly fit with zero slop the new motor axle, I recommend either drilling a hole in them to make them into pinching dropouts or fabricate pinching torque plates to bolt to the swingarm to clamp it securely. (torque arms or plates are required so you don't have axle spinout (and destroy the wiring from motor to controller, often also destroying the controller and other devices from the electrical short). There are a few threads describing this type of thing, starting with The Torque Arm Picture Thread.

They don't state the axle size, but most "ebike" motors use a 10mm axle flat, and this one says it takes regular bicycle freewheels that have to fit over bicycle axles, so you probably would have to make those pinching torque plates since your MC axle is probably larger diameter than that, and the motor axle would just spin in your dropouts instead of driving the bike.

There are multiple axle shoulder spacings available on the page, so you need to make sure you get the right one for your swingarm.

My main question is about brakes. The website is pretty vague on details, so I couldn't figure out how braking works. The bike currently has a rear drum brake, which will be removed for the new wheel. Do I need to add a disk brake?

If you want a rear brake, then if your frame doesn't have caliper mounts (probably doesn't) you'd have to design and make or have made a disc caliper adapter for motorcycle disc brakes (which are typically hydraulic instead of cable-operated like your drum brake probably is, so you'll also need the hose and fluid and new lever on the bars or foot control (whichever you use) to match it).

You'll also have to buy the tophat adapter they show on the page for a motorcycle type rotor,

If you know you can rely on only a front brake for your purposes you could skip the rear brake, but if you're nto certain of it I wouldn't recommend it for most MC usages I can think of.

Do those motors have built in braking?

Some controllers support regen braking, but most of them only have on/off braking at some preset level, leaving you with no real control over it. The ad doesn't specify, so it probalby only does this.

More advanced (expensive, harder to setup, etc) controllers support variable regen braking, to give more control.

Both depend on your battery being able to accept momentary high-current charging from the controller without damaging the BMS, cells, etc, to create the load on the motor that creates the braking force.

A few of the advanced controllers (FOC types) can actively brake by using power instead of regenerating it to the battery, by opposing the rotation of the motor...but if things aren't setup correctly in the controller, and it isn't tuned for your specific motor correctly, it could damage the controller.

The kit appears to come with two brake levers, presumably for rear and (front?) brakes. I will be leaving the front drum brake as is.

Those are probably only for bicycle brake cables; if so you will need to keep your front drum lever and cabling. They're also probably made for bicycle handlebars, and may not fit on your MC bars. Same for the throttle in the kit, and the clamps for the display.

riding in bike lanes rather than in traffic, etc

You might not be able to get away with that where you live; I'd recommend checking your local laws and LEO attitudes (and local cyclists, since they may not agree with a motorcycle in their lanes) about them first.

 

[HagridsButtquack]

If your dropout slots don't perfectly fit with zero slop the new motor axle, I recommend either drilling a hole in them to make them into pinching dropouts or fabricate pinching torque plates to bolt to the swingarm to clamp it securely. (torque arms or plates are required so you don't have axle spinout (and destroy the wiring from motor to controller, often also destroying the controller and other devices from the electrical short). There are a few threads describing this type of thing, starting with The Torque Arm Picture Thread.

They don't state the axle size, but most "ebike" motors use a 10mm axle flat, and this one says it takes regular bicycle freewheels that have to fit over bicycle axles, so you probably would have to make those pinching torque plates since your MC axle is probably larger diameter than that, and the motor axle would just spin in your dropouts instead of driving the bike.

There are multiple axle shoulder spacings available on the page, so you need to make sure you get the right one for your swingarm.

Thanks for your very thorough answer. The axle being a smaller diameter is something I hadn't even considered so I'll definitely have to look into that as well. I know these kits have been used by people on small motorcycles, but hopefully someone that has used one of these motors before can chime in with their experience.

Ideally I would like regenerative braking if possible, but I guess I'll have to check with them and see if these motors have it since it doesn't specify. If you do get regenerative braking, can that alone serve as your rear brake? And then I can get away with just having the front drum brake?

 

[E-HP]

I don't want to have to get a degree in electrical engineering in order to build the thing so a kit seems like an easy and simple solution. My main question is about brakes. The website is pretty vague on details, so I couldn't figure out how braking works.

How are you mechanical/welding/metal fabrication skills? On the link you provided, in the middle of the page, are the components needed for a rear disc brake conversion, but I suspect you will need to weld/bolt something on the swingarm to mount the disc caliper since you currently have drums.
The motor is capable of regen, since it is direct drive. But, you need a regen capable controller to implement it, and I'm not sure the Leaf kit controllers have that feature (but it looks like they use "DC MOTO CONTROLLERBYLITHIUMBATTERY" controllers, that folks on the forum have modified for regen). Regen on typical controllers won't bring it down to 0 mph, but to around walking speed, and you'll need actual brakes to stop completely. Higher end controllers can go down to 0 mph, but not sure what your budget is, but you won't get it with the kit controller.
A motorcycle conversion is more challenging than a bike conversion, even with a kit, since motorcycles aren't as standardized so there's often metal work involved, but I'm eager to see how it goes.

 

[HagridsButtquack]

How are you mechanical/welding/metal fabrication skills? On the link you provided, in the middle of the page, are the components needed for a rear disc brake conversion, but I suspect you will need to weld/bolt something on the swingarm to mount the disc caliper since you currently have drums.
The motor is capable of regen, since it is direct drive. But, you need a regen capable controller to implement it, and I'm not sure the Leaf kit controllers have that feature (but it looks like they use "DC MOTO CONTROLLERBYLITHIUMBATTERY" controllers, that folks on the forum have modified for regen). Regen on typical controllers won't bring it down to 0 mph, but to around walking speed, and you'll need actual brakes to stop completely. Higher end controllers can go down to 0 mph, but not sure what your budget is, but you won't get it with the kit controller.
A motorcycle conversion is more challenging than a bike conversion, even with a kit, since motorcycles aren't as standardized so there's often metal work involved, but I'm eager to see how it goes.

Thanks. My mechanical skills are solid, I've been working on old cars and motorcycles for a long time. I've done very little to no welding though. If the regen could get it down to walking speed I could use the front brake for a full stop. I'll have to look into if I need to modify the controller or not, that seems doable.

 

[E-HP]

Thanks. My mechanical skills are solid, I've been working on old cars and motorcycles for a long time. I've done very little to no welding though. If the regen could get it down to walking speed I could use the front brake for a full stop. I'll have to look into if I need to modify the controller or not, that seems doable.

Coincidentally, I was looking at Thundercamel's update to his "StefEbike" build thread, and noticed he has a DCMoto controller, which I think the brand Leaf kits uses. Anyway, he modded his for regen, soldering a couple wires on the board so you may be able to get some idea about how to mod yours or inquire about how low a speed the regen is good for.

StefEbike for my wonderful disabled wife

Thanks Chalo, Good to know you haven't seen steel ferrules either. I at least did learn to grind the housing ends flat from Sheldon Brown in time for the repair. Looks like I forgot to mention that I helped build another eBike in April; this time for my wife's stepdad whom I get along well...

endless-sphere.com

 

[amberwolf]

Ideally I would like regenerative braking if possible, but I guess I'll have to check with them and see if these motors have it since it doesn't specify.

It isn't the motor that "has regen", it's the controller. As long as the motor is a DD rather than geared motor (such as with all the Leaf motors I know of), it can physically do regen.

As noted previously, what kind of regen you get depends on the controller, and it's likely that this one, if it has it at all, is only on/off at some factory-preset level. Usually these also have some lower cutoff speed at which they cease trying to brake, and some of them may have an upper speed they will not brake beyond. They often don't have a very high braking current, so may not be enough to replace a mechanical brake. Some of them don't respond quite instantly to braking control inputs--they often start braking instantly, but may not stop braking instantly (or may stop braking but not start motoring afterward instantly upon throttle command).

More advanced ones may have more advanced braking options as well.

If you do get regenerative braking, can that alone serve as your rear brake? And then I can get away with just having the front drum brake?

Honestly you'll have to test it on your specific build under your conditions and riding style to see if it does what you want.

How well it may work depends on the controller's regen current capability and your battery's ability to accept that current without damage (and the battery's internal resistance--lower is better for both braking and acceleration), and the motor's ability to generate the current from the speed you're decelerating from. And the ability of all of those to do this repeatedly as often as necessary for your riding style and conditions.

The higher the current generated, the more braking force there is. The faster you're going, the higher that current is likely to be, decreasing as you slow down. For common controllers using on/off braking with no variable control, for those few that have a high braking current capability, the sudden full braking force from high speed could be pretty high. Under poor traction conditions, it can cause loss of control.


It takes a certain amount of power to create an acceleration force, and a similar amount to have a similar braking force. For example, if you need to stop from a certain speed in a shorter distance than it takes you to acclerate to that speed, the braking current generated has to be higher than the acceleration current.


Typically, most braking is done with the front brake. If your riding style and conditions require a rear brake or you use it more than the front, then you probably need it to be as strong *and modulatable* as possible, up to the point it breaks the tire's traction to the road--once it starts to skid it doesn't matter how much braking force is generated, because it isn't doing anything for you anymore.

Modulation requires variable regen, so if the controller you use only has on/off regen, it won't work for that. So you should decide before buying anything whether you want that modulatability of braking or if you are ok with sudden full force braking every time regardless of road/traction conditions, etc.

 

[HagridsButtquack]

If your dropout slots don't perfectly fit with zero slop the new motor axle, I recommend either drilling a hole in them to make them into pinching dropouts or fabricate pinching torque plates to bolt to the swingarm to clamp it securely. (torque arms or plates are required so you don't have axle spinout (and destroy the wiring from motor to controller, often also destroying the controller and other devices from the electrical short). There are a few threads describing this type of thing, starting with The Torque Arm Picture Thread.

They don't state the axle size, but most "ebike" motors use a 10mm axle flat, and this one says it takes regular bicycle freewheels that have to fit over bicycle axles, so you probably would have to make those pinching torque plates since your MC axle is probably larger diameter than that, and the motor axle would just spin in your dropouts instead of driving the bike.

So I checked with them and they said the kits have a 14mm diameter axle, which coincidentally is exactly the same as my existing axle so it should work without any modifications. I think I'm just gonna use the front brake for now and eventually figure out regen braking or a rear brake.

My only question at this point is which motor to get. You can see here that they have 3 motors options. 48/52v 1500w, 48/52v 2000w, and 60v 2000w. I've been trying to figure out what the difference between those would be and my best understanding is that a higher wattage will give more speed and power at the cost of using more energy, while a higher voltage will give more speed but less power? Please correct me if I'm wrong, and which one of those 3 do you think would be the best option? Again, this will just be for casual running around, doesn't need to go very fast or carry much weight.

 

[amberwolf]

So I checked with them and they said the kits have a 14mm diameter axle, which coincidentally is exactly the same as my existing axle so it should work without any modifications.

If your existing axle is 14mm, then that means the axle flats on a hubmotor (which are almost always 10mm apart) will just spin inside your dropouts unless you make torque plates or pinching dropout plates, etc., to bolt or weld to your frame.

The hubmotor axle diameter (it's round part) isn't what matters in relation to your existing droputs, it is the distance between the two flat sides of the axle.

That flat part must be very securely clamped in place, as any rotation/movement at all will eventually damage either the securing mechanism or the axle enough to allow it to just spin in place when accelerating or braking, instead of the wheel doing this, and rip your wires up, shorting out the motor, controller, etc. (usually destroying the controller and often the motor halls and anything else that was connected to the controller's 5v (throttle, etc).

The axle shoulder width also matters--this needs to match the distance between the inboard faces of the dropouts, between the two halves of the swingarm. If it's too wide it won't fit in your swingarm. If it's too narrow you won't have enough axle length to secure into the swingarm's dropouts.

My only question at this point is which motor to get. You can see here that they have 3 motors options. 48/52v 1500w, 48/52v 2000w, and 60v 2000w. I've been trying to figure out what the difference between those would be and my best understanding is that a higher wattage will give more speed and power at the cost of using more energy, while a higher voltage will give more speed but less power?

It doesn't work quite like that.

Watts = power.

Power (watts) = Volts x Amps.

More volts for the same amps is still more power.

More amps for the same volts is still more power.

More Volts (voltage) *generally* = more speed, but *only* if the motor winding (kV, Rpm/Volt) and wheel/tire diameter and current are the same between two different-voltage-options.

More Amps (current) *generally* = more torque, but *only* if the motor winding (kT, Torque/Amp) and wheel/tire diameter and voltage are the same between two different-current-options.

Reality is more complicated, and exactly what you get depends on the actual riding conditions and the speed you're going, so to see how this works, experiment with the motor simulator over at ebikes.ca.

Whether you can even use the more power or more current or more volts in a particular system or set of conditions depends on those conditions and the stuff (electric and mechanical) you've got and how it's configured.

Please correct me if I'm wrong, and which one of those 3 do you think would be the best option? Again, this will just be for casual running around, doesn't need to go very fast or carry much weight.

I can't really guess which would do what you want. Phrases like "Very fast" and "much weight" are highly variable depending on the person talking, and we don't know what that means to you. To me, not going very fast means say, 5-10mph. Not carrying much weight to me means only a few hundred pounds, including the trike or bike, me, and the dog or cargo. (fast would be >20mph, and a lot of weight would be >1000lbs, with several hundred pounds of cargo).

If you don't want define the job you need it to do, and use one of the simulators to at least guesstimate how much power you *actually need* to do the job you need the bike to do for you, then you are better off going for the highest power you can get, so you aren't at least totally disappointed in performance. It might be enough power, or it might not.

Don't forget you'll need a battery that can do more than what the system will ever ask of it, because it will age and be less capable as it does so (the cheaper the battery, the lower quality it probably is, and the faster that aging is likely to happen). So starting out with one that's better than you need means it can still do what you want for some time. The battery is the heart of the whole system, so if it can't do what you need it to, the system definitely can't.

Even better, starting out with one that's even more capable than that by some large margin means it might still be usable with a higher power system if it turns out that whatever you get now doesn't do the job you need, so you're not having to buy *everything* twice (just the controller/motor).