Seeking Advice: Converting 27.5" MTB to eBike with 500W Motor for Family Rides

[redbike]

Hi everybody,

I purchased a new mountain bike with 27.5-inch wheels and would like to convert it into an eBike. I already have a 36V 19AH battery from my old bike's cyclotistry kit that I plan to reuse. My main usage of the eBike will be on paths and cycles with my family, so I'm not aiming for off-road capabilities.

After some brief research, it seems like I'd benefit from more power and torque. I'm considering a 500W geared motor with a low BPM for uphill ect (i am a heavier rider ).

I'd appreciate any advice or suggestions on the best options for the rear motor, controller, and other components to make this conversion a success. Thank you in advance for your help!

Any advice on selecting the right motor, controller, and other components for my needs would be greatly appreciated. Thank you for your input!

 

[saneagle]

It's a shame you already have the battery because 48v would have been better. Without knowing your actual weight and level of fitness and steepness of hills, it's not possible to say how much current you need. You have to bear in mind that the size of controllers goes up along with the amount of current they're rated for, then you have to figure out where you're going to put it. Here's what a 25A one looks like. I build this bike 11 years ago for a forum member, who only had one leg. It's now with its second owner, who doesn't look after it even though it's his only transport, but it's still going strong:

 

[redbike]

I'm 105kg but sometime but also have my 3 year old on the back so other 16kg ish, my old 250w with 36v front wheel motor was pretty good only struggled on the steeper hills really, just as need new motor thought I get a little more power .

 

[Az.]

I build this bike 11 years ago for a forum member, who only had one leg. It's now with its second owner, who doesn't look after it even though it's his only transport, but it's still going strong:

You put a lot of effort into that bike. It is sad to see how it looks now.
Battery cover is falling apart.

 

[saneagle]

You put a lot of effort into that bike. It is sad to see how it looks now.
Battery cover is falling apart.

That's the kids today. They don't care about anything and expect everything to be done for them. This guy is 38 years old, has never had a job, spends all day every day playing computer games and has grown to 20st as a result of that. Now he's gobbling up national health resources trying to get all the resulting and increasing health problems sorted.

 

[Nealh]

Before you do anything you need to know the continuous current rating the battery can out put ,this will be different and lower then the batteries peak out put.
Continuous and peak output are very different, peak output is the max current the battery can output temporarily say for 30 secs.

As for a 500w hub over a 250w motor one doubts if you will notice much difference unless one can apply 25 -30a to the 500w hub .

 

[redbike]

Before you do anything you need to know the continuous current rating the battery can out put ,this will be different and lower then the batteries peak out put.
Continuous and peak output are very different, peak output is the max current the battery can output temporarily say for 30 secs.

As for a 500w hub over a 250w motor one doubts if you will notice much difference unless one can apply 25 -30a to the 500w hub .

Thanks Nealh for the info, how do you about testing that?

 

[Nealh]

One will generally go by the battery specs of the cells and the BMS specs fitted to the battery. They would have been or should have been available from the vendor.

 

[saneagle]

Thanks Nealh for the info, how do you about testing that?

Where did you get the battery from? If you recently bought it, show us the listing.

 

[Terol Jiang]

hello, you can purchase the Bafang rear wheel hub motor kits, it including all the ebike components, like rim motor, controller, display, speed sensor, cutoff brake, throttle, ect.

 

[redbike]

I got the kit from https://cyclotricity.com/uk/custom-mix-match-your-own-conversion-kit.html i will email them asking if they have the details of the battery, as no info on the website that i can see

 

[saneagle]

I got the kit from https://cyclotricity.com/uk/custom-mix-match-your-own-conversion-kit.html i will email them asking if they have the details of the battery, as no info on the website that i can see

Yes, like most UK sellers they don't give any useful info about their stuff. It says suitable for 500w motors, do we can assume it's good for at least 22A.

I think it would be a good idea to look at your present controller to see what's the maximum current it allows. You can then estimate how much current you need. Let's say that your present controller allows 15A, then a 17A one would give 13% more climbing power, a 22A one 50% more, a 25A one 66%, and a 30A one double the power.