What controller for more amps?

I put together my first ebike, Specialized SX trail. I had bought a BBSHD but it doesn't fit this frame as the BB has too much reinforcement. I had a cheap Chinese 48v 1500w rear hub kit and 48v 14.5ah battery I had grabbed off craigslist and I'm really enjoying this cheap introduction to ebiking.
I bought the kit new in box, but off craigslist so I'm not sure exactly what kit I have - there are no specs or "brand name" etc. Can anyone tell me how many amps I'm probably sending to the motor? I'm assuming 20?
I've read these hubs can take quite a bit of power. Can someone give me a suggestion of what specific controller would be a nice upgrade? I was thinking of 35 or 40amps would really wake this bike up, giving more torque/speed for quick bursts. I won't be doing long hill climbs or going WOT for miles at a time so I'm not too worried about ruining the motor. (plus it was super cheap)
And maybe a small capacity battery that can provide 35-40amps continuous? Most of my rides are just exercise rides after work half hour to an hour. I would think a 10ah battery would be plenty, but I can go bigger if you guys suggest it?
Would you guys stay at 48v or does something else make more sense?
Thanks in advance.

It's hard to say without knowing some of the specifics of the motor such as: magnet height, rpm/volt and diameter. We can generalize and say many motors with a "1500W" rating will probably be around 25-35mm magnet height and the common 205mm diameter.

If the motor fits that category; it can probably take 1000-1800 watts continuous and 2000-4000+ peak. It depends on how efficient it is.

I highly recommend a programmable controller so you can set the max battery and phase current levels. Most of the inexpensive "KT" style controllers can do that. Then you can dial it in to suit your battery and motor needs. I'd probably start with something like 35A battery / 85A phase and see how hot it gets. Increasing it in small increments (5 to 10 amps).

Would something like this work?
https://www.amazon.com/Cozyel-Electric-Bicycle-Brushless-Controller/dp/B07MS143GY/ref=sr_1_3?dchild=1&keywords=2000w+ebike+controller&qid=1626454721&sr=8-3

or this? (It says 40a, but also says 1000w, which scares me it won't be powerful enough???)
https://www.ebay.com/itm/173439354097?hash=item2861ca84f1:g:8LYAAOSwFC1daM5F

And again my kit only has the three lights on the throttle, no display. These more powerful controllers would let me have a display, correct? How does one tell which ones are compatible?

Thanks for your help!

slm9s said:

Can anyone tell me how many amps I'm probably sending to the motor? I'm assuming 20?
I've read these hubs can take quite a bit of power. Can someone give me a suggestion of what specific controller would be a nice upgrade? I was thinking of 35 or 40amps would really wake this bike up, giving more torque/speed for quick bursts.

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Well 48volts x 40amps = 1920 watts.
So that’s probably what your controller is pushing now. Most 1500w kits output anywhere from 35 to 45amps maximum current. The rated current is lower.

If you have a battery that could handle it maybe 50 or 60amps would be more of what you’re looking for. Also with those hub motor kits they’re typically a 3T winding so they don’t have great acceleration. I’ve been down that road with a couple of those Motors.

Any specific controller recommendations? What have you guys used that worked well? Do those two I linked above look like good options, or should I look for 50 or 60a?

Typically, "48v 1000w" kits came with 30 amps controllers. The motors that come with them tolerate this pretty good,, 48v x 30 amps is approximately 1500w.

Yes, you can push more into those motors, up to 72v 40 amps. But if you run more than say, 2000w, you can melt a motor down in about 45 min. Fortunately, the cost and weight of a 72v battery that will last 45 min makes it more likely to run out in 30 min. 72v 10 ah lasts about 30 min is what I mean.

My advice is to run what you got, because I bet you a hundred bucks your battery already is getting hammered into dogshit by 30 amps. 40 amps is going to mean you buy a new battery before the snow flies.

Lastly, that cheap ass battery,,,, charge it outside. Ok to bring it in once charged, or if not charged yet. But charge it outside. Seriously.

First of all, I use my ebikes for actual mountain biking / exercise. I'm not using this as a motorcycle or commuting, its on trails so I rarely use the throttle for sustained periods.

Second, on my wife's bike the controller is bigger than mine and is labeled 17amps - I assume mine is the same or less.

Third, I understand I would have to buy a better battery. This battery was thrown in with the kit I bought used off CL.

My thinking is that a 40a controller matched with a quality 48v battery capable of 40 or 50a continuous would be a big step up in performance. I understand that the motor couldn't take full throttle for extended periods but I wouldn't use it like that.

Am I mistaken? Will the controllers I linked above give what I'm proposing? Can anyone link what controller they would recommend instead?

Thanks guys!

You probably could just mod your actual controller to feed much more power, by adding an extra shunt and beefing the traces. The question is: can your battery supply this extra current?

DD motors can take a lot of power when they are on the heavy side, fast winding and smaller wheels especially. From 16 lbs and up (motor alone), you can feed them bursts of 10kw in acceleration. From 30 lbs and up, it is pretty safe to double that. Only you need to be conscious of how long your motor can take such power before overheating. Many of us had to fry a few to know how much is too much, and how long is too long. If you can’t control yourself, better set the controller limit to control you. :wink:

slm9s said:

First of all, I use my ebikes for actual mountain biking / exercise. I'm not using this as a motorcycle or commuting, its on trails so I rarely use the throttle for sustained periods.

Second, on my wife's bike the controller is bigger than mine and is labeled 17amps - I assume mine is the same or less.

Third, I understand I would have to buy a better battery. This battery was thrown in with the kit I bought used off CL.

My thinking is that a 40a controller matched with a quality 48v battery capable of 40 or 50a continuous would be a big step up in performance. I understand that the motor couldn't take full throttle for extended periods but I wouldn't use it like that.

Am I mistaken? Will the controllers I linked above give what I'm proposing? Can anyone link what controller they would recommend instead?

Thanks guys!

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I won't do the first second third thing, but you can't judge the power/current of a controller by size (maybe if they are the same manufacturer). The phaserunner is capable of 90A peak, 45-50A continuous, and is about the size of a pack of cigarettes.

For offroad riding, I only use throttle, since PAS will get you in trouble in technical sections. With a direct drive motor, you need to keep an eye on the heat. Even pedaling hard, when ascending a 25% grade, the motor can heat up quickly. Statorade is a must.

Short answer is yes it's better than what you have and looks big.

Don't know anything about the controller outside reading what the specs are. It should max out your motor at 48v and get it really hot at 72v with a matching battery.

slm9s said:

Any specific controller recommendations? What have you guys used that worked well? Do those two I linked above look like good options, or should I look for 50 or 60a?

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I have an 18FET KT, 30A continuous, 40A max, and it will provide 40A for a good while without getting hot/warm. I used it with a 52V battery, so about 2000W. The controller never got during the whole time I used it, and climbed a lot of hills. Out of the two, I'd choose the KT, but mainly because I like my bike to run silent.