From 250W to 350W

[mifletz]

One option to increase the power of a little 250W e-bike is said to be to change its controller to a 'smart' one, thereby enabling access to the battery's 36V*11A full 350W power.

Has anyone had any experience of this: does it work?

 

[Alan Quay]

All controllers are smart. Their job (among other things) is to control the amount of currrent that the motor receives.

Most 250w/36v bikes operate at a maximum of 15 amps.

The battery will have a maximum continuous current that it can supply. It doesn't matter what controller you have, if you exceed this limit the BMS in the battery will shut it down.

So the answer is: Changing the controller to a more powerful one will increase performance, but if it's more than your battery can deliver, it will cut out. You also risk burning out your motor, although most can handle a bit more than stated.

 

[Deleted member 4366]

One option to increase the power of a little 250W e-bike is said to be to change its controller to a 'smart' one, thereby enabling access to the battery's 36V*11A full 350W power.

Has anyone had any experience of this: does it work?

Tell us what battery, motor and controller you have and we can tell you how to get more power.

You're correct that you can get more power by changing the controller, but you have to be careful. The 250w or 350w designations are misleading. Some 250w controllers will give more power han some 350w ones. What's important is the maximum current that they will allow.

More power from the controller will not necessarily increase your speed. Assuming that there's no speed restriction, the speed is limited by the motor. You can use a 1000w controller, but it won't make your motor spin any faster.

 

[mifletz]

I don't have a bike yet, but what will be needed is greater slope-climbing ability rather than more speed. 250W just doesn't cut a 30 degree slope.

Is it correct that provided one changes to the correct controller, most 36V 250W motors can be used with 48 volt batteries without burning out, resulting in a substantially improved performance?

 

[trex]

you'll need a lot more than 350W to climb a 30 degree slope.

 

[Deleted member 4366]

Yes. You will get 33% more speed and climbing torque, but there's a downside. A hub-motor becomes ineffecient wgen it runs at less than 50% of its max speed. Say you have a motor that can reach 20 mph, but it's restricted to 15 mph. It will be inefficient at full throttle below 10 mph. When you go up to 48v, it will be inefficient below 13 mph. The further you go below 50% max speed, the worse the efficiency, so the higher the chance of burning out the motor and the more battery you waste.

If it's just hill-climbing you want, it might be better to just increase the current.

If you're thinking of changing the battery and controller, it would be better to get the right kit in the first place and convert a normal bike rather than try and adapt an electric bike.

 

[Alan Quay]

you'll need a lot more than 350W to climb a 30 degree slope.

...and a cable car.

 

[Deleted member 4366]

you'll need a lot more than 350W to climb a 30 degree slope.

My 250w Xiongda motor can do it fairly easily at 15 amps with a bit of pedalling. You just need the right 250w motor.

 

[Alan Quay]

Where have you found a 58% hill?

 

[Deleted member 4366]

I guess we all mean 30% hill.

 

[trex]

30% is roughly the gradient of public staircases.
it's steeper than the average perception.

 

[Deleted member 4366]

We have three hills of 30% or more on my regilar bike rides including te infamous Lincoln Hill that averages 15% over 500 meters.

 

[trex]

it's one thing to have enough power for a short and steep hill, you'd need a lot more power to keep going on a 30%. The battery will disconnects soon enough.

 

[Deleted member 4366]

I don't understand what you're trying to say. The battery will disconnect when it's empty whether you're on a hill or not.

 

[mifletz]

For a 250W motor, would the extra amps from a 36V 15A battery gain any extra power and torque over a 10A battery? Or just extra range?

For extra hill-climbing ability is the voltage the main determinant?

 

[Deleted member 4366]

In a word, no; however, there would be a very slight gain because the battery would be always at a slightly higher voltage. The difference would be maybe 1% when fully charged, but could be as high as 10% after 20 or more miles. If you want more climbing power, you might be able to solder the shunt in your controller, which could give 30% more torque. The 15Ah battery would be better if you did that.

 

[trex]

the drop in climbing power shows up on your bike's LCD battery meter.
The voltage display drops a bar or two or even three when you ride up a steep hill. The sag is inversely proportional to the capacity.