250W 15A motor, 15A controller, 48V 15Ah battery with 30A BMS compatibility?

[leakimc]

Hello everyone. I'm asking for advice on the compatibility of the following parts. I'm planning on a 250W 15A front hub motor, a 15A or a 20A controller and a 48V 15Ah battery with a BMS of 30A. The parts are not very powerful due to Finnish traffic laws.

• First, should my controller current be higher than my motor current to avoid stressing the controller if the motor draws a higher peak current?
• Second, is the 30A BMS enough for a 15A (or a 20A) sine-wave controller? The cells are Samsung 21700 cells.

I would greatly appreciate any advice. Thank you.

 

[E-HP]

Motors are rated for power (watts), not current, so I wouldn’t worry about the 15A motor “rating”. The combination of components looks fine. Your battery BMS rating is slightly above the capabilities of the cells in the pack, but by using a 15A controller, you be less likely to stress the battery, so that works out well.

 

[leakimc]

Motors are rated for power (watts), not current, so I wouldn’t worry about the 15A motor “rating”. The combination of components looks fine. Your battery BMS rating is slightly above the capabilities of the cells in the pack, but by using a 15A controller, you be less likely to stress the battery, so that works out well.

Thank you for the informative reply! It seems like I misunderstood how the motor works. However, since P=UI, do amps not contribute to the power of the motor? I'd be interested to know more since the internet holds conflicting information. Also, you said "less likely to stress the battery"; is pulling 15A from the battery in question sub-optimal or potentially unsafe? Thanks again.

 

[E-HP]

Motor current and battery current are two different things. When the motor is running at less than full throttle, voltage going to the motor is lower (voltage going to the motor determines its speed). When you twist the throttle under load, while the motor is trying to speed up, it can draw up to 3 times the current as the battery current (since power from the battery will roughly equal power consumed by the motor plus losses, and voltage to the motor is less than the battery, more current is needed). If that 15A was a real motor rating, then you should get a 5A controller if you’re worried about the motor.

 

[99zip99]

What happened to President Biden for some reason let's say you had a glass of water you have 15 oz and you have 20 oz what can you have a longer drink from ?
The 20ah the battery can only give as much power as the controller demands see we call that the controller.

 

[leakimc]

Motor current and battery current are two different things. When the motor is running at less than full throttle, voltage going to the motor is lower (voltage going to the motor determines its speed). When you twist the throttle under load, while the motor is trying to speed up, it can draw up to 3 times the current as the battery current (since power from the battery will roughly equal power consumed by the motor plus losses, and voltage to the motor is less than the battery, more current is needed). If that 15A was a real motor rating, then you should get a 5A controller if you’re worried about the motor.

Right. If I were to get a battery that was 48V and 20Ah instead of 15Ah, would it make changes needed to the configuration or would it simply up the theoretical range of the battery? I'm still a bit confused in general when it comes to what numbers to look out for in controllers, motors, and batteries (amps, volts, etc.). There's a lot of conflicting information as to what will overheat and which limits concern which components.

So far I've gathered that:

• my controller voltage and amps shouldn't be a lot higher than my battery's current and voltage output to prevent overheating
• motor voltage and amps shouldn't be higher than controller voltage and amps to preserve the controller, however, I'm a bit confused over the motor not having a real current rating.

Excuse the incoherent questions, but I would appreciate a quick overview of which electrical attributes and values have significance concerning which components and the basic principles on which they function. Again, I appreciate the information you've given so far.

 

[99zip99]

You want a nuts and bolts answer give us the nuts and bolts.
What bike are we talking about what motor are we talking about what controller are we talking about what gauges are we talking about ?
We need a link to the bike and motor you're talking about it could be locked ?
Give us a link to where you bought it what kid it is or what controller you have.
You might be able to disconnect the speed limit wire and go faster and stronger ,? This is only a maybe
Maybe you can put $750 Watts into this motor or you can you can put 2,000 watts into this motor it would just melt sooner than if you put 250 Watts

 

[leakimc]

You want a nuts and bolts answer give us the nuts and bolts.
What bike are we talking about what motor are we talking about what controller are we talking about what gauges are we talking about ?
We need a link to the bike and motor you're talking about it could be locked ?
Give us a link to where you bought it what kid it is or what controller you have.
You might be able to disconnect the speed limit wire and go faster and stronger ,? This is only a maybe
Maybe you can put $750 Watts into this motor or you can you can put 2,000 watts into this motor it would just melt sooner than if you put 250 Watts

Nuts and bolts are what I'm going for exactly my friend. I haven't bought anything yet though. Here's all the information I'm able to gather about the parts:

Motor:

• I was thinking about going for a 250W, 48V, 15A option. This current rating was given by the manufacturer (Green Pedel, China). The motor is front hub, brushless and geared.
• Model is called GP-G24

Battery:

• Samsung INR21700-50E cells
• Battery pack: 48V, 15Ah
• Battery pack case: DP-2170-4C, so by my calculations a 13S3P configuration, and a maximum current output of 29,4A
• BMS stated to be 30A

Controller

• Integrated in the down tube battery mount
• 48V, 15A/20A
• sine wave
• 6 "better powered" mosfets (15A) or 9 "better powered" mosfets (20A)

I appreciate the help.

 

[E-HP]

Right. If I were to get a battery that was 48V and 20Ah instead of 15Ah, would it make changes needed to the configuration or would it simply up the theoretical range of the battery? I'm still a bit confused in general when it comes to what numbers to look out for in controllers, motors, and batteries (amps, volts, etc.). There's a lot of conflicting information as to what will overheat and which limits concern which components.

For a battery pack, the voltage, capacity, and discharge current capability are important for specs, and the type of cells, pack configuration, and construction are important physical specs.
15Ah combined with the voltage, 48V, provide the amount of stored energy and therefore range; so 15x48 = 720Wh or stored energy. The discharge current capability is measured in amps (A), represents the current that the pack can provide continuously, when combined with the voltage, provide how much power the pack can provide, so if the pack has a current capability of 30A, the pack can deliver 48x30 = 1440W.
In an example where both the 20Ah and 15Ah packs are constructed with same cells, then the 20Ah pack will have a higher discharge current capability than the 15Ah pack by 20/15 = 1.333. This is because the pack must have more cells in parallel to result in the greater capacity, and those additional cells increase the discharge current capability in addition to increasing the stored energy (this is where pack configuration and cell type come into play).
So using the 20Ah and 15Ah packs as an example, made of cells that can store 2500mAh, or 2.5Ah each and the ability to discharge at 5A, you can determine the pack configurations as 13S8P and 13S6P respectively.
13S means you need 13 cells in series to achieve 48V nominal. 8P and 6P results in 8x2.5 = 20Ah and 6x2.5 = 15Ah.
Current discharge current capability, similarly results in 8x5 = 40A discharge current capability and 6x5 = 30A discharge current capability.

So, the most important thing to look for in a battery pack is the cell type used and the pack configuration. Everything else is just math.

 

[leakimc]

For a battery pack, the voltage, capacity, and discharge current capability are important for specs, and the type of cells, pack configuration, and construction are important physical specs.
15Ah combined with the voltage, 48V, provide the amount of stored energy and therefore range; so 15x48 = 720Wh or stored energy. The discharge current capability is measured in amps (A), represents the current that the pack can provide continuously, when combined with the voltage, provide how much power the pack can provide, so if the pack has a current capability of 30A, the pack can deliver 48x30 = 1440W.
In an example where both the 20Ah and 15Ah packs are constructed with same cells, then the 20Ah pack will have a higher discharge current capability than the 15Ah pack by 20/15 = 1.333. This is because the pack must have more cells in parallel to result in the greater capacity, and those additional cells increase the discharge current capability in addition to increasing the stored energy (this is where pack configuration and cell type come into play).
So using the 20Ah and 15Ah packs as an example, made of cells that can store 2500mAh, or 2.5Ah each and the ability to discharge at 5A, you can determine the pack configurations as 13S8P and 13S6P respectively.
13S means you need 13 cells in series to achieve 48V nominal. 8P and 6P results in 8x2.5 = 20Ah and 6x2.5 = 15Ah.
Current discharge current capability, similarly results in 8x5 = 40A discharge current capability and 6x5 = 30A discharge current capability.

So, the most important thing to look for in a battery pack is the cell type used and the pack configuration. Everything else is just math.

That makes sense. I believe this is the configuration of the cells (Samsung INR21700-E50) in the case (DP-2170-4C):



I used a calculator to see more info about the battery pack and saw that the max voltage would be around 54V. Is that a problem for the 48V controller?

 

[E-HP]

I used a calculator to see more info about the battery pack and saw that the max voltage would be around 54V. Is that a problem for the 48V controller?

Batteries and controller are described by their nominal ratings. So a "48V" battery in your example has range of 13x4.2 = 54.6V max and 13x2.5 = 32.5V min, with 13x3.6 = 46.8V being nominal. Some cell manufactures use 3.6V and but more use 3.7V as the nominal voltage of a lithium ion cell, so 13x3.7V would 48.1V nominal, rounded to 48V. A 48V controller made for lithium ion batteries assumes this range to be within it's specs (32.5V to 54.6V), although the lower voltage value may differ depending on where the controller manufacture sets the low voltage cutoff.

 

[99zip99]

Great you haven't bought it yet. Do you want a European step through ? Do you want to touch bike with the Baskin in the front for a person ? Do you want a 20-in x 4-in tire how much is the rain how often will you be riding in the snow ? I always like 48 volt but then again I run 72 volt
These motors seem to like 48 volt over 36 volt. In my opinion.
They even have an adapter for a winter or it has a track like a snowmobile on a bike frame adapter.
I have a brother that lives in Norway above the Arctic circle. He has retired on the Norwegian retirement benefit plan as a doctor. Now there's a retirement plan.
Hey he just wishes Finland would quit sending over the Russian immigrants over to Norway. Haha as they just walk over in the winter. I guess there's less mosquitoes ?

 

[leakimc]

Great you haven't bought it yet. Do you want a European step through ? Do you want to touch bike with the Baskin in the front for a person ? Do you want a 20-in x 4-in tire how much is the rain how often will you be riding in the snow ? I always like 48 volt but then again I run 72 volt
These motors seem to like 48 volt over 36 volt. In my opinion.
They even have an adapter for a winter or it has a track like a snowmobile on a bike frame adapter.
I have a brother that lives in Norway above the Arctic circle. He has retired on the Norwegian retirement benefit plan as a doctor. Now there's a retirement plan.
Hey he just wishes Finland would quit sending over the Russian immigrants over to Norway. Haha as they just walk over in the winter. I guess there's less mosquitoes ?

I think a nice aluminum hybrid frame would be good and versatile, with no basket or anything. I think Putin should stop flooding the North with immigrants in the first place though. Mosquitoes suck.

 

[99zip99]

Do you have a bike to start with ?
Show us a pic or a picture of your ideal bike will it be used in the snow and the rain ?

 

[leakimc]

Do you have a bike to start with ?
Show us a pic or a picture of your ideal bike will it be used in the snow and the rain ?

I don't have a bike yet, but thinking of something along these lines:



I would want the bike to be able to function in the winter, but it wouldn't be driven in deep snow, mostly urban areas. The parts are waterproof according to the manufacturer.

 

[99zip99]

Those are both 29 in ? I can't read the name of the picture. Plus how fast you want to go but a three-speed switch on it will get you up to 30 mph no problem.
The battery is the heart of an e-bike so get a good heart.
I love my Bluetooth BMS that way I can monitor the health my battery.
I figured out how to get my photo up there but I don't know how to get my name off of there I wonder if a mod can help ? Yes that's a Polish last name Norwegian and laplander. My niece in Norway is named Hedwick slubowski. Yeah you can raise that part of the sentence too.

New item by Robert Slubowski

photos.app.goo.gl

 

[leakimc]

Those are both 29 in ? I can't read the name of the picture. Plus how fast you want to go but a three-speed switch on it will get you up to 30 mph no problem.
The battery is the heart of an e-bike so get a good heart.
I love my Bluetooth BMS that way I can monitor the health my battery.
I figured out how to get my photo up there but I don't know how to get my name off of there I wonder if a mod can help ? Yes that's a Polish last name Norwegian and laplander. My niece in Norway is named Hedwick slubowski. Yeah you can raise that part of the sentence too.

New item by Robert Slubowski

photos.app.goo.gl

Finland's speed limit is 25 km/h, so it wouldn't have to be very fast. Also it would be pedal assist only, no throttle.

 

[99zip99]

I couldn't have a bike without a throttle.

 

[d8veh]

Hello everyone. I'm asking for advice on the compatibility of the following parts. I'm planning on a 250W 15A front hub motor, a 15A or a 20A controller and a 48V 15Ah battery with a BMS of 30A. The parts are not very powerful due to Finnish traffic laws.

• First, should my controller current be higher than my motor current to avoid stressing the controller if the motor draws a higher peak current?
• Second, is the 30A BMS enough for a 15A (or a 20A) sine-wave controller? The cells are Samsung 21700 cells.

I would greatly appreciate any advice. Thank you.

That should all work OK; however, there is something you need to think about. Generally front motors work quite well with low power, but if you run too much power through one, they lose traction, which wears out the tyre really quickly and the wheel will always slip on gravel, grass and any other compromised surface. For that reason, a rear motor is better if you have the choice.

Also, the torque from the motor can break the fork drop-outs, which is very dangerous. I've seen it happen a few times. In normal aluminium suspension forks, you can go up to around 36v at 20A or 48v at 15amps as long as you have at least one torque arm. Any more than that requires steel forks.

Your motor doesn't have a current, it can probably handle around 22 amps at 36v or 18 amps at 48v. You can go higher but you have to be more careful to keep it running at its efficient speed , and there's always a chance of stripping the plastic gears inside, though they don't cost too much to replace.

The bikes you have chosen are not really suitable for a front motor, and for that sort of motor, a 26" wheel would be better, otherwise it might lack torque and run inefficiently.

 

[Chalo]

Generally front motors work quite well with low power, but if you run too much power through one, they lose traction, which wears out the tyre really quickly and the wheel will always slip on gravel, grass and any other compromised surface. For that reason, a rear motor is better if you have the choice.

Eh, I think the difference is overrated. Most of my bikes have had front hub motors, at power levels up to 2500W electrical. As long as there's weight on the driven wheel, it's manageable. Skidding does wear the tire faster for sure.

One point in favor of a front hub motor is that hub motor wheels are always weaker than normal bike wheels of like construction (same rim, same spokes). Since the rear wheel has a harder job to do, it makes sense to use the stronger wheel in the rear.

Also, the torque from the motor can break the fork drop-outs, which is very dangerous. I've seen it happen a few times. In normal aluminium suspension forks, you can go up to around 36v at 20A or 48v at 15amps

I would not do that. No aluminum or magnesium suspension forks with any kind of hub motor that doesn't have an integrated torque arm. Heck, I've snapped the tips of forks like that by installing a wheel that had axle nuts instead of a quick release skewer. Not worth the risk in my opinion.

 

[d8veh]

Eh, I think the difference is overrated. Most of my bikes have had front hub motors, at power levels up to 2500W electrical. As long as there's weight on the driven wheel, it's manageable. Skidding does wear the tire faster for sure.

OP has a geared motor. The higher torque makes them slip. DD motors are not so bad, but the bigger axle breaks aluminium forks very easily unless you have good reinforcement.

It's difficult to keep weight on the front wheel when you're going up a hill, which is when you need the power the most. OP is talking about getting a normal MTB, not some special cargo bike with added front weight.

 

[leakimc]

I would not do that. No aluminum or magnesium suspension forks with any kind of hub motor that doesn't have an integrated torque arm. Heck, I've snapped the tips of forks like that by installing a wheel that had axle nuts instead of a quick release skewer. Not worth the risk in my opinion.

Thanks for the input. I read an article by Ebike School talking about torque arms on hub motors. According to them, a 250W front hub with aluminum forks should be fine with a sturdy stainless steel torque arm. Here's a quote:

"Like we discussed above, 250 watts or less should be fine in nearly any steel or aluminum dropout without torque arms."

What do you think?

 

[E-HP]

I think they have a pretty good write up about Endless Sphere and how to participate in the forum.
I think a front fork failure at speed can be life changing.
I think you need to make the best decision for yourself in order for natural selection to work as it should; although personally I’d use one.

 

[leakimc]

I think they have a pretty good write up about Endless Sphere and how to participate in the forum.
I think a front fork failure at speed can be life changing.
I think you need to make the best decision for yourself in order for natural selection to work as it should; although personally I’d use one.

My question isn’t about whether I should use one or about my willingness to risk my health. That’s unrelated to this topic. It’s about if having a proper torque arm would provide sufficient reinforcement even for an aluminium fork at 250W.

 

[n00b]

I couldn't have a bike without a throttle.

Pedal assist can get you killed. Launched right off a curb into traffic. I've been setting up my pedal for take off
for so long, not changing that to have pedal assistance.