Hi all. I was wondering, since a motor only draws the amount of amps it need for a given load, having a controller with a higher max amp capability should not reduce range if it is ridden the same way (meaning you still accelerate at the same rate). However, when going uphill, the more powerful controller will be able to maintain a higher RPM and therefore higher motor efficiency. So in an area with a few mild hills, a more powerful controller should not affect the range negatively, correct? I ask before I install a 35 amp Infineon from ebikes.ca to replace my stock Chinese 20 amp.
Higher amp controller=more range...?
- Thread starter e-troll
- Start date
major
10 kW
If you ride up the hills faster you will use more energy or Wh/mile so your range will likely decrease, but you'll arrive at your destination sooner. I doubt that a change in efficiency would offset the increase in load.
major
10 kW
e-troll said:
I would say that is correct.
dogman dan
1 PW
Off the hill, cruising in no bad wind, a given speed will take a given wattage. For example, 400w gets most bikes about 20 mph.
So with a 48v 10 amps controller, 400w is about 9 amps. With a 48v 100 amps controller, 400w is,,,,,, about 9 amps. So there is no penalty in range for having a big controller you aren't using any more amps from. No benefit either. If you start up faster, then it costs you, but it could be well worth it.
On the hill, all anybody can really say is it depends. It depends on the motor winding, the rim size, the weight of the rider, the grade of the hill, the voltage you are running, if the battery can stand it, and the type and or size of motor. Oh so fun running any kind of valid experiment with 8 variables besides the 9th variable, controller amps.
So you have to go test it with you, on your bike and motor, on your hill, with your battery. But some generalizations emerge. IF you are now stalling the shit out of that motor, more amps will help your motor maintain speed up that hill. In that case, faster may well be less power, because you were previously running at about 10% efficiency. Get efficiency back up to 60%, and it helps.
If you have a typical direct drive hubmotor, and you get up that hill at 15 mph, you are doing ok. You don't need more amps. If you are slowing to below 10 mph, you are about to melt that motor. The solution if you have wicked hills may be to get both a bigger controller, and to run a slower winding motor. If you want to keep the top speed the same, then that means more volts to get to that same speed with the slow motor.
Or, get really huge motor, and heave huge watts at it, and fly up the hill. Works great, but not particularly good for great range.
But I digress. You said mild hills. Again like on the flat, if getting up that hill is only taking you say 18 amps, then the bigger controller will get you up the hill using ,,,,,, wait for it,,,,,, 18 amps. If the hill was taking you 22 amps, the typical max real world amps of 20 amps controllers, then a bigger controller might get you going up the hills at 27 amps. Then we get back to , does the motor run more efficient at 27 amps, at that grade, with you on that bike? It could well be that climbing the hill faster at 27 amps is better.
So if you know what amps you are using going up those mild hills, you can better decide. If you are not maxing amps on those hills, a big controller will not help you much. A given motor on a given grade with a given weight rider may never pull more amps than you already use, unless you change other variables like the winding or the voltage. If you only use 18 amps now, a 35 amps controller won't go faster up that hill.
The best way to ride and get more range is to use a wattmeter. Then you can learn where your watts are wasted, and where they aren't. Changing your riding style can make huge gains in range, even if you go about the same speed as before.
So with a 48v 10 amps controller, 400w is about 9 amps. With a 48v 100 amps controller, 400w is,,,,,, about 9 amps. So there is no penalty in range for having a big controller you aren't using any more amps from. No benefit either. If you start up faster, then it costs you, but it could be well worth it.
On the hill, all anybody can really say is it depends. It depends on the motor winding, the rim size, the weight of the rider, the grade of the hill, the voltage you are running, if the battery can stand it, and the type and or size of motor. Oh so fun running any kind of valid experiment with 8 variables besides the 9th variable, controller amps.
So you have to go test it with you, on your bike and motor, on your hill, with your battery. But some generalizations emerge. IF you are now stalling the shit out of that motor, more amps will help your motor maintain speed up that hill. In that case, faster may well be less power, because you were previously running at about 10% efficiency. Get efficiency back up to 60%, and it helps.
If you have a typical direct drive hubmotor, and you get up that hill at 15 mph, you are doing ok. You don't need more amps. If you are slowing to below 10 mph, you are about to melt that motor. The solution if you have wicked hills may be to get both a bigger controller, and to run a slower winding motor. If you want to keep the top speed the same, then that means more volts to get to that same speed with the slow motor.
Or, get really huge motor, and heave huge watts at it, and fly up the hill. Works great, but not particularly good for great range.
But I digress. You said mild hills. Again like on the flat, if getting up that hill is only taking you say 18 amps, then the bigger controller will get you up the hill using ,,,,,, wait for it,,,,,, 18 amps. If the hill was taking you 22 amps, the typical max real world amps of 20 amps controllers, then a bigger controller might get you going up the hills at 27 amps. Then we get back to , does the motor run more efficient at 27 amps, at that grade, with you on that bike? It could well be that climbing the hill faster at 27 amps is better.
So if you know what amps you are using going up those mild hills, you can better decide. If you are not maxing amps on those hills, a big controller will not help you much. A given motor on a given grade with a given weight rider may never pull more amps than you already use, unless you change other variables like the winding or the voltage. If you only use 18 amps now, a 35 amps controller won't go faster up that hill.
The best way to ride and get more range is to use a wattmeter. Then you can learn where your watts are wasted, and where they aren't. Changing your riding style can make huge gains in range, even if you go about the same speed as before.
dogman dan
1 PW
Also consider your battery. Will it tolerate 40 amps spikes on an uphill start? It better be big, or high discharge rate for a big controller.
chas58
10 kW
I use a 14 watt controller to limit my watt usage and consumption. I supply the additional power when needed.
More amps means more power useage If you don't have it you can't use it. If you do have it, you will use it, unless like Dogman suggested you get a meter and use it to restrain yourself. But what would be the point of getting a bigger controller if you don't use it?
You might be able to solder the shunt to get a little more current out of your current controller
More amps means more power useage If you don't have it you can't use it. If you do have it, you will use it, unless like Dogman suggested you get a meter and use it to restrain yourself. But what would be the point of getting a bigger controller if you don't use it?
You might be able to solder the shunt to get a little more current out of your current controller
dogman dan
1 PW
Very true. a tiny blob of solder on the shunt will get you close to 30 amps, for no money. Might try that first.
Also true, if you have it you will use it. I ride a 40 amps controller on my big cargo bike, to power up a huge motor. But 90% of the time, I ride with speed limited to 18 mph, and double my range compared to having 40 amps, and going 33 mph. Because of the motor, even just 48v has me blasting, getting about 40 wh/mi.
Those 40 amps blasts off the stop sign are so fun, I just keep on doing it. If I need that extra range, I can't have those extra amps.
Also true, if you have it you will use it. I ride a 40 amps controller on my big cargo bike, to power up a huge motor. But 90% of the time, I ride with speed limited to 18 mph, and double my range compared to having 40 amps, and going 33 mph. Because of the motor, even just 48v has me blasting, getting about 40 wh/mi.
Those 40 amps blasts off the stop sign are so fun, I just keep on doing it. If I need that extra range, I can't have those extra amps.
Thanks dogman for your informative posts. I got the bigger controller because the vast majority of the time I ride in the city. I like having that extra power there even though I usually manage to refrain from using it. In traffic though, it's nice to be able to hit the throttle for one or two seconds to get in front of someone. It's not optimal for my battery, but like I said, I usually refrain. I occasionally ride to the suburbs to visit family. It's that 20+ mile ride I have only ever done on the 20 amp controller. Experiment I shall. I'm am super broke right now so I'll have to wait until my loans for next semester come in so I can invest in a cycle analyst. It should put an end to my range anxiety once and for all.
That's more or less correct in theory. When a motor's struggling up a hill, its efficiency can drop to about 30%, by using more current to increase its speed, efficiency can climb to 60%, so you could end up going faster up-hill and using less battery. The controller uses a speed control algorithm to send power to the motor, so when you open the throttle, it gives high current initially, which reduces as your speed approaches that set on the throttle, so, when setting off and accelerating, you'll use a lot more battery because the current will be higher. Plus, you'll enjoy the extra current, so you'll just be using it because it's available rather than going at the same speed as before.e-troll said:
As Dogman points out, if your battery can't give the current, the voltage will sag, so ypu'll be back to where you were powerwise, or worse still, the BMS will cut-off, leaving you to pedal without power. Check your battery rating, or tell us what it is, and we can advise max current.
dogman dan
1 PW
You can get inexpensive watt meters on ebay for less than 20 bucks including the shipping.
On that long ride, just ride slow, and the amps of your controller won't matter. Less wind resistance will lower the wattage it takes, and at 200-400w, you will never be using that many amps. To extend range even further those days, when you stop pedal the first ten feet, then give throttle. That will guarantee your motor never pulls much more than 10 amps the whole ride.
Fun to play the hypermile game once you have a wattmeter to show what you have done. You make a challenge of it, like this trip I will ride with no more than 10 amps max. Or try to ride with less than 200w. Or just shoot for better and better wattours per mile. Try slow and steady, fast and coast, etc and see what happens.
On that long ride, just ride slow, and the amps of your controller won't matter. Less wind resistance will lower the wattage it takes, and at 200-400w, you will never be using that many amps. To extend range even further those days, when you stop pedal the first ten feet, then give throttle. That will guarantee your motor never pulls much more than 10 amps the whole ride.
Fun to play the hypermile game once you have a wattmeter to show what you have done. You make a challenge of it, like this trip I will ride with no more than 10 amps max. Or try to ride with less than 200w. Or just shoot for better and better wattours per mile. Try slow and steady, fast and coast, etc and see what happens.
chas58
10 kW
good advice!
