Limit Speed But Keep It Consistent Even Going Uphill

[death by bacon]

What affects speed? What affects climbing power? I want to build an ebike but limit its speed to 25kph but I still want it to be able to climb hills and reach 25kph. Is it possible to do this using generic front/rear hub ebike kits? What settings need to be modified to achieve this?

 

[portals]

What affects speed? What affects climbing power? I want to build an ebike but limit its speed to 25mph but I still want it to be able to climb hills and reach 25kph. Is it possible to do this using generic front/rear hub ebike kits? What settings need to be modified to achieve this?

My home built donor ebike has a rear hub 1500W and 52V 17.5Ah battery, I can pedal PAS to get to say 25mph then hold down button for cpl secs to put it in cruise mode and it will keep to 25mph on hills unless it's a 'really' steep hill in which case I give it full throttle and pedal to give it a hand.

 

[amberwolf]

If you just want to limit speed, then pick a controller, motor, and battery that will easily do the worst-case climbing job at the speed you want (or better), and then just setup the speed limit in the controller (if it has one) to what you want to limit to.

If the controller doesn't have a speed limit, you can build a device to read wheel speed and then roll back throttle if this speed is exceeded until it's not. Or buy the Cycle Analyst from ebikes.ca that is designed to do this (and a bunch of other things you probably don't need, but some others which are useful to almost anyone with an ebike).

Ebikes.ca also has a motor simulator, that once you learn a bit about how it works (it has instructions) you can use it to figure out how much power, etc that you will need to do the job you have to have the bike to, so you can more easily get the right parts for the job.

 

[death by bacon]

My home built donor ebike has a rear hub 1500W and 52V 17.5Ah battery, I can pedal PAS to get to say 25kph then hold down button for cpl secs to put it in cruise mode and it will keep to 25kph on hills unless it's a 'really' steep hill in which case I give it full throttle and pedal to give it a hand.

This is the exact setup I was going for - 1500w, 52v, rear wheel hub.

That's actually a good idea using the cruise mode. Can the speed for the cruise mode be setup manually on the get go? What controller/kit are you using to make this possible?

 

[death by bacon]

If you just want to limit speed, then pick a controller, motor, and battery that will easily do the worst-case climbing job at the speed you want (or better), and then just setup the speed limit in the controller (if it has one) to what you want to limit to.

If the controller doesn't have a speed limit, you can build a device to read wheel speed and then roll back throttle if this speed is exceeded until it's not. Or buy the Cycle Analyst from ebikes.ca that is designed to do this (and a bunch of other things you probably don't need, but some others which are useful to almost anyone with an ebike).

Ebikes.ca also has a motor simulator, that once you learn a bit about how it works (it has instructions) you can use it to figure out how much power, etc that you will need to do the job you have to have the bike to, so you can more easily get the right parts for the job.

Exactly. I am going for a 1500w rear wheel hub, and 52v battery.

Is there an out-of-the-box device/controller like that where you can setup different modes? E.g. Mode 1 for limited speed but good climbing. Mode 2 for full power, etc.

 

[amberwolf]

If you just limit speed, it doesn't limit power. (you could also limit power if necessary, but there's not usually a need to do so unless your control system (throttle, pedals, etc) doesn't give you the ability to modulate that power well enough for some circumstances.)

For instance, on my SB Cruiser trike, I always have full power (around 3-4kw) available, but the Cycle Analyst I use to let me control the system via pedal cadence (not the same as typical PAS, but actual variable control) is also set to limit speed to 20mph. It's not a cruise, just a limit, so I am riding at whatever speed I want to via the pedals just like any unpowered trike, except that I'm making the motor do the work for me. (it has a cruise if you want it, but I ride in traffic, s where the speed has to change all the time, so cruise isn't useful or safe).

I'm just using "dumb" controllers with no setup or programming or display/etc., and the CA does all the modulating and limiting for me. It's more expensive, but it is more versatile for my usage. If you don't want a display, the CA can be put wherever you like, you don't have to ever access it while riding. (if you need a way to change settings you can use a remote button setup on the handlebars).

If you prefer a cheaper alternative, the KT series of controllers can probably do what want (pretty sure you can set a speed limit on them). If not with the OEM firmware, you can use the open-source firmware OSFW (there are several threads around the forum about that), and I *think* you can buy them preloaded with that.

The Lishui OSFW can probably also do this, don't know if the OEM FW can.

Both of those use displays to change modes, set them up, etc., not sure if you can run them "headless" (no display) without just running the default settings rather than your own custom ones. (you'd have to look up the threads for them to verify that if you don't want a display).

 

[E-HP]

What affects speed? What affects climbing power? I want to build an ebike but limit its speed to 25kph but I still want it to be able to climb hills and reach 25kph. Is it possible to do this using generic front/rear hub ebike kits? What settings need to be modified to achieve this?

Is the hill a speed bump or a mountain?

Slow wind nine continent with statorade will do 10% indefinitely, but adding hubsinks would be a good idea

Motor Simulator - Tools

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

ebikes.ca

 

[stancecoke]

What affects speed? What affects climbing power?

Speed is limited by the motors Kv constant. With a certain battery voltage, the motor can spin a certain rpm. The max speed on an E-Bike is set in the controller normally. The motor could spin faster, but the controller cuts the power, if the speed is over the limit. (therefore tuning dongles are very popular )
Climbing power is limited by the motor current. The motor torque is directly proportional to the motor current. The higher the Kv the lower the torque per amp constant. You can push a high current through the motor for a short time, but this will heat up the motor and the controller. So you have to reduce the current after a while to prevent the system from overheating.
The efficiency of a BLDC motor is bad at low speed, so make sure that you don't fall below 10kph uphill with the hub motor. If the motor is too weak to keep this speed, you should think about a middrive system.
See this maxon paper for some theory:

https://www.maxongroup.com/medias/sys_master/8798985748510.pdf

regards
stancecoke

 

[E-HP]

See this maxon paper for some theory:

https://www.maxongroup.com/medias/sys_master/8798985748510.pdf

regards
stancecoke

Thanks for that link. It puts the concepts together in one place/reference. Great stuff! I'm going to add it to my newb thread.

 

[portals]

This is the exact setup I was going for - 1500w, 52v, rear wheel hub.

That's actually a good idea using the cruise mode. Can the speed for the cruise mode be setup manually on the get go? What controller/kit are you using to make this possible?

This is the kit:
https://www.moddsebikes.co.uk/product/26-48v-1500w-rear-wheel-conversion-kit/

This is the battery:
https://www.moddsebikes.co.uk/product/52v-17-5ah-lithium-battery-and-charger-high-quality-cell/


To use cruise control with that controller and display you need to be moving at least 12mph, then start pedalling and when getting near to the speed you wnt to cruise at hold the down button for 2secs and a C lights up and bike will keep it at that speed.

I use one ebrake on left rear for safety at lights and didn't bother to fit the right front ebrake, so I can use this right brake to temporarily slow down without leaving cruise mode (the ebrake kills cruise.battery immediately).

There is a thread somewhere I posted on this last year, if I can find it I'll post link

EDIT: I said 25kph in earlier posts, I meant 25MPH so have edited them, I can cruise easily at 25mph as long as no bad headwinds or dodgy road surface.

 

[portals]

You will also need two torque arms, bin the cheapo(s) that you get with bike kit and buy thicker better fit ones, one per side. I had to design my own for drive side as using an old donor bike

Here is link to my build thread so you can see the kit on bike:
Thoughts on This eBike Kit and Battery

Bike has been hibernating over the winter with a steady battery charge decrease from 80% to about 57% so all good. Never did get around to buying mudguards as no likey the rain, hoping to get back out on it when the weather turns and try out my new £10 Zefal Dooback right side wing mirror.

 

[999zip999]

Or 72v 20ah 60watt controller and 3,00wat motor is one way. So maybe 3,800 Watts up a hill. But you know that's a lot of weight. But this is one way to skin a cat.
Oh 38mph up my hills. 80lbs oh no.