Performances of different controllers question?

[ebike11]

Hi guys
Im new at experimenting with different controllers, batteries etc and I had a question between 20A and 30A controllers.When I swapped my 20A for a 30A I could notice the torque difference right away. Naturally the 30A will eat my battery much faster. However, Im probably wrong, but is most of the extra battery drain with the 30A over the 20A from the start off to mid throttle?? If so, would both the 20A and 30A drain take about the same battery powered wide open throttle since the speed is maxed out with each controller??? Just wondering where I can try and save on battery life if I stick with the 30A controller. The controller and motor are both 48V and motlr is 500W hub bafang motor.
Thanks

 

[footloose]

Great question, thank you for asking it.
I don't have the answer, but I have been wondering about the same question.
Seems like slow/gradual acceleration from stop would naturally conserve battery,
and if you are conservative enough it doesn't really matter 20 vs 30 amp controller.
And once the bike is rolling at speed and controller/battery are basically just maintaining speed,
or accelerating gently (on a flat road, not into a headwind, etc) amp capacity
of controller doesn't really mean much.

If true, then having a 30 amp versus a 20 amp controller means you can "goose it" when
you need to for acceleration... or be conservative, accelerate gently, and not burn any more battery
with a 30 than 20.

Well, that's logic. Interesting to hear what people who understand controllers better think.

 

[Animalector]

yep... at max speed if the system is only drawing 15A (for example) it doesn't matter which controller you use the power consumed will be the same (assuming a long ride at max speed)

As you have identified, the difference comes with the acceleration, and up-hill work, where the 30A controller has more power available and therefore will drain the battery faster.

Get a 30A, and just don't floor it when accelerating. (ie gradually twist your throttle)

Enjoy.
Andy

 

[friendly1uk]

Not really on topic, but are you using a 48v battery? 48V and 30A sounds a lot for a 500w motor.

Don't throttle it off the line, as the motor is very inefficient when it is barely moving. You can feel it doing very little, yet pulling full power. What your actually doing is making heat. Try and pull off using the pedals, even if you do like to ride it like a motorcycle once your moving.

 

[ebike11]

Not really on topic, but are you using a 48v battery? 48V and 30A sounds a lot for a 500w motor.

Don't throttle it off the line, as the motor is very inefficient when it is barely moving. You can feel it doing very little, yet pulling full power. What your actually doing is making heat. Try and pull off using the pedals, even if you do like to ride it like a motorcycle once your moving.

Yes 48v10.4ah battery and 48v 500w motor

Do you think its a lot? My friends have 36v350w bafangs and they are putting even more battery power. They are also running 30a controllers. They seem to be running fine

 

[friendly1uk]

Oh, OK then. I will go with proved over read
I also have a 500w bafang, A geared one, the cst. I have been noting peoples opinions, which seem to revolve around 30A at 36V but with a reduction at 48v. Weather and hills all come in to play though. I will take your finding onboard. Thank you

 

[ebike11]

Oh, OK then. I will go with proved over read
I also have a 500w bafang, A geared one, the cst. I have been noting peoples opinions, which seem to revolve around 30A at 36V but with a reduction at 48v. Weather and hills all come in to play though. I will take your finding onboard. Thank you

No no, please dont follow my noob advice haha Im new at this and all I know is my friends are running 36v350w with
lots of batt. power But other members on here may have more reliable info and real life motor results

 

[JennyB]

yep... at max speed if the system is only drawing 15A (for example) it doesn't matter which controller you use the power consumed will be the same (assuming a long ride at max speed)

As you have identified, the difference comes with the acceleration, and up-hill work, where the 30A controller has more power available and therefore will drain the battery faster.

Get a 30A, and just don't floor it when accelerating. (ie gradually twist your throttle)

Enjoy.
Andy

I can think of a case where the 30 amp might give better range:

Hills are steep enough that 15 amps cannot keep the motor in its most efficient range, or
To maintain your desired average speed you need to go much faster elsewhere to make up for time lost on the hills.

Energy needed to overcome gravity is independent of speed: energy needed to overcome air resistance increases with the square of speed.

I haven't yet tested that myself. :?

 

[dogman dan]

Under certain circumstances, that can be true.

Example, my longtail weighs 150 pounds with a full 40 pound battery load. On grades up to 7-8% I can ride it up hills very efficiently while still in the speed limiting mode. I max out at about 1000w with the 18 mph speed limiter loop plugged in. On the flat, more like 300w.

But the other day, I went to a place with two miles of 13% grade! No way could the 1000w haul 330 pounds up that grade faster than 5 mph. 5 mph at 1000w meant turning about 500w of that into heat. Opening up the controller to it's full 40 amps, I was able to climb the grade at 15mph, turning only 200w or so into heat. A 300w per hour savings. Those numbers are estimates btw.

But, the most efficient way to get up a long steep hill is generally to use as little power as it takes, to keep going at your motor's moderately efficient rpm. This varies from motor to motor, but for typical hubmotor kits, you don't want to climb a steep hill less than 12-15 mph. So half throttle on the 30 amps controller, or 20 amps controller may still be more efficient than full throttle up the hill. If you are maintaining 15 mph, going faster won't be more efficient.

On the stop signs, yes, you will use more power if you use full throttle from the stop and 30 amps. But, it gets you to the full speed pretty quick, and you might find it doesn't make that much difference in your range if the ride is flat. Worth it in any case, to not have that ol familiar sluggish take off.

You battery might choke and die on 30 amps, if it's small and 2c. And 48v 30 amps, is 1500w. More than your motors clutch is really designed for.

 

[d8veh]

That's right. Nearly all the wasted battery happens at low speed, so in some circumstances you can save by going faster. You'll find that you can only draw the maximum current at low speed. At cruising speed, it'll probably be half as much, even at full throttle. The throttle doesn't control the current. It controls the speed. You need to fit a wattmeter to see what happens to the current.

I also have a 500w bafang, A geared one, the cst. I have been noting peoples opinions, which seem to revolve around 30A at 36V but with a reduction at 48v. Weather and hills all come in to play though. I will take your finding onboard. Thank you

The advice is more for the type of riding you do. For the Bafang CST 36v 30A will give cruising at just over 20mph and enough torque to tackle very steep hills. 48v 23 amps will give a 33% higher speed and more or less the same torque for hill-climbing, although not so efficient. The Zofo clone seems happy at 64v 30A, so the Bafang should be able to do the same or more. Obviously, the more power you put through the motor, the shorter it's life, but I think it's current that can do more damage than voltage provided that you're sensible in the way you use the bike.

 

[heavymetalthunder]

Seems like to me you might consider installing a watt meter and see your actual power usage in various conditions. I find for me I tend to accelerate about the same as car traffic in the slow lane. I usually adding pedal power up to 15 MPH.