What's the right controller for my e-bike?

[tiagormp]

Good day everyone, I don't have knowledge on e-bikes and I bought a bike off facebook marketplace, however it needs some work and I'm having the hardest time ever to find useful information on what kind of controller, kit and battery to use with the hub wheel motor it came with.

It came with an 8FUN 36V250W SWXK Bafang Front Electric Wheel Hub Motor
https://www.aliexpress.com/item/32698286404.html

Can someone please point me to the right direction? I haven't found much information on the controllers I could use with this motor, as there are so many options available on AliExpress.

I'd like to build the most simple conversion possible, not looking for anything fancy.. I believe just the thumb throttle and LCD would be fine, but again, as I don't have much knowledge on e-bike I don't really know what would work and what I need to make this ebike working.

Any assistance is appreciated. Thanks :wink:

 

[amberwolf]

Good day everyone, I don't have knowledge on e-bikes and I bought a bike off facebook marketplace, however it needs some work and I'm having the hardest time ever to find useful information on what kind of controller, kit and battery to use with the hub wheel motor it came with.

It came with an 8FUN 36V250W SWXK Bafang Front Electric Wheel Hub Motor

Can someone please point me to the right direction? I haven't found much information on the controllers I could use with this motor, as there are so many options available on AliExpress.

I'd like to build the most simple conversion possible, not looking for anything fancy.. I believe just the thumb throttle and LCD would be fine, but again, as I don't have much knowledge on e-bike I don't really know what would work and what I need to make this ebike working.

What do you want the bike to do for you? How much do you have to spend on it?

What else does the bike already have on it besides the motor? (not just the electric--is the rest of the bike complete?)

Those are the main things that will determine which controller/battery to get for it, and any other accessories you may need.

The motor numbers provided mean it is meant to run on 36v to give a certain speed in a certain wheelsize (neither of which is given in the motor numbers, unfortunately, but it's not uncommon for 20mph to be the speed, and the size should be whatever wheel it's already in if it came that way). The 250w means it's a pretty low power motor; it is meant for a max continous of 250w, though it can probably handle short infrequent bursts of twice that, and may be able to run at something more than 250w for long periods. Mostly the problem with running motors higher than their ratings (especially small geared hubs like these) is that they get hot inside faster than they can get the heat out, and can be damaged by that.

In general, with this small a motor, if you have no specific requirements, you could get any basic 36v or 48v battery and the same voltage kit (meaning controller, LCD, throttle, pedal sensor, ebrake levers, etc., and whatever connectors are needed to plug the battery and motor into the kit (it's quite possible that they won't have the same plugs). It's possible the motor has a 9-pin Julet connector on it, which is pretty common in the "Waterproof plug" type kits, but you can buy the controller-side cable for about $15 or less if you end up needing it (you'd splice in the controller side wiring to that new cable).

Given the motor size of 250w, it's safe to use a 36v controller that has an 7-8A rating, because 250w / 36v = 7A. That way there isn't a risk of overheating the motor on higher loads like hills, etc. If it's a 48v battery, then I'd go with a 5-6A controller (250w / 48v = 6A).

The battery will need to supply however much current (A) that the controller will ever use, continuously. if you're sticking with a 250w system, then worst case with the above you'd need one that can supply 8A. Most of them can probably do that easily enough.

That 8A is a different spec than the Ah rating the battery will also have. The Ah is how long it can keep supplying that 8A before it's empty. So if you had an 8Ah battery, it could do full power for a whole hour (and since it doesn't usually take the full power all the time, it would probably last up to a couple hours under those conditions).

The cheaper the battery, for the same specs, the more likely it is to be more cheaply made, and last less time and/or be less reliable. Unfortunatley just because it costs more doesn't mean it's better; it's hard to know how good one will be until you actually use it for a while. The battery is the heart of the system, in that all the power for everything the system does has to come from it, when it's needed, and if it isn't there the system can't do the job you need it to.


So...for us to help you pick a specific system, it would be best if you can give as many specifics of how you need to use the bike and in what situations, as well as how much range you need from it, and your budget.

 

[tiagormp]

Thank you for your quick response, I appreciate you taking some time to help!!

Yes, bike is complete and I've been using it for quite some time with no issues... I'm looking forward to get this bike converted to commute to work mainly, It's pretty flat where I live, so.. I'm ok not having a super strong motor or a really large, heavy battery... I was hoping to have at least 25 km range with a single charge and as I said before, I'm looking for the most simple setup possible. there are so many controllers available and I'm not sure what I need to make the motor running.

I really don't have a budget, as this is my first ebike conversion, I would say I'd like to spend as little as possible and hopefully I would invest in a better setup, once I've learn a bit more.

Regards,
Tiago

 

[999zip999]

So it's running now ?. But just with a weak battey ? The motor and the controller are okay ? More info and a link or pictures. You can buy an e-bike tester for 15.00. May have to get a matching plugs for tester . We need more info. Start with a multimeter. Do you have one ? Test and let us know the charger voltage. Then battey. Set the meter voltage higher then testing like 100 volts or more
Give us more info about the bike send some pics or a link first and that's going to really help us

 

[amberwolf]

Yes, bike is complete and I've been using it for quite some time with no issues...

I"m assuming "complete" means just the bike itself, not the electrics?

Do you have anything electric other than the motor already?

What connector does the motor have on it? This will help us help you find one that has the right connector so you can just plug it in, if possible, or if not, an easy-to-install set of connectors for both motor and controller.

I'm looking forward to get this bike converted to commute to work mainly, It's pretty flat where I live, so.. I'm ok not having a super strong motor or a really large, heavy battery... I was hoping to have at least 25 km range with a single charge and as I said before, I'm looking for the most simple setup possible. there are so many controllers available and I'm not sure what I need to make the motor running.

I really don't have a budget, as this is my first ebike conversion, I would say I'd like to spend as little as possible and hopefully I would invest in a better setup, once I've learn a bit more.

OK, if it's pretty flat, and you don't have any speed you need to reach beyond typical pedal speeds (presumably, usually around 25km/h or less), then the only two big limiting factors on what to get are the battery capacity to reach that 25km range, and something simple that doesn't require much setup or a lot of stuff to put on the bike to operate it.

The simplest systems don't have any display, and so have no settings or levels to the assist--you control them entirely by the throttle. Motor configuration on them is done via "learn" wires that you connect with the wheel offground, wait for the motor to spin the right way, then disconnect and leave that way. If that sounds like what you are looking for, then we can poke around to find one of those, once we know what motor connector you have and what else electric you've already got (and what connectors are on them).



It's pretty likely that that motor will do 25km/h (maybe a little more) on 36v, if it's in a 26" wheel. (a smaller wheel will be slower). 25km/h should take around 20wh or less per mile, depending on conditions and whether you help by pedalling or not. It may take much less, perhaps only half that (my Crazybike2 only took about 20-30wh/mile to go 20mph cruise). So to go 25km at that power consumption would be 25 * 20, or 500wh. SInce many batteries are rated in Ah instead of Wh, that's 500wh / 36v = 13.9Ah.

At a guess, this is likely to cost between $250-$500 for a good one; you may find ones half that price or less, but I don't know how good they will be. You might get by with as little as 7-8Ah, depending on how you use the bike, and so it will cost that much less.

Some random examples of styles (I don't have any recommendations yet):
https://www.amazon.com/BAFANG-Electric-Bicycles-Battery-250W-500W/dp/B07VGRWNXV
https://www.amazon.com/36v-ebike-battery/s?k=36v+ebike+battery
I recommend one that comes with a frame mount that you bolt or clamp to the bike and slide the battery casing into, so that you can take the battery off the bike with you when you aren't with it (it should make the bike less of a theft target without the battery, and if you do lose the bike you at least have a battery for the next one), and can take it inside for charging too. These things are essentially never waterproof, so keeping them out of the rain is a good idea.

If you prefer to carry it in a backpack (they're kinda heavy, so most poeple don't want to do this) with a longer cable to the bike, you can use the brick kind, often just shrinkwrapped in blue, and definitely not waterproof. They can also be mounted on the bike but they're harder to make so that you can take them off easily.




If you need to go faster than that by motor power, then you can use a 48v battery, and that will probably reach 30-32kmh, maybe more. Depends on the motor winding and the controller power you have available, and the conditions (wind, hills, weight).

Since it will take more power to go faster, then you may need a slightly higher capacity battery (in Wh) to get the same range.