More powerful geared hub drive?

[rocketman58]

I have a 500w / 48v Bafang G020 geared hub drive on my recumbent trike. I have it pared with a KT controller to avoid the odd speed limitations of the stock controller. For casual riding it is great. However when riding with others at higher speeds over more aggressive terrain I am finding it coming up short. (Think lots of steep short hills and varying terrain). The G020 has a 45Nm rating where as most mid rives have a rating at least double that. So why not just go with a mid drive? I have some physical limitations that are not compatible with the wider Q required by DIY mid drive kits. I have also ruled out a DD motor due to the added weight. Ideally I would like a geared hub motor that produces closer to 80Nm, lets me use a KT controller, has a cassette body, and still fits in my trikes 135mm rear dropouts. I know Grin has a few premium options but they are out of my price range. Any other other suggestions?

 

[lnanek]

Are you sure it's the hub? I routinely run my 750W motor at 2800W without any overheating issues. Maybe you need a battery and controller that support more amps max discharge.

 

[rocketman58]

The motor is stamped 500w / 48v. Would everything work if I used a higher AMP controller and a 52w battery? I wouldn't want to destroy anything. Would I see a significant power increase if I did something like this?

Would I be better off just using a higher assist level more often? I had been using level 1 & 2 (out of 5), but due to declining health I find myself more often in 2 & 3.

 

[neptronix]

Typically you can run 2-3x the rated power from a stop on any geared motor and get away with it. They just can't handle dramatically much more than stock continuously.
Could probably quite easily get another 20-30nm out of it safely with some more amps.

Get a controller that is programmable so that you can bump up the amps to taste.

If you have higher assist levels available to you, you might as well use them instead of start messing with the controller at all. That should have the effect of increasing power somewhat.

 

[E-HP]

I have a 500w / 48v Bafang G020 geared hub drive on my recumbent trike. I have it pared with a KT controller to avoid the odd speed limitations of the stock controller. For casual riding it is great. However when riding with others at higher speeds over more aggressive terrain I am finding it coming up short. (Think lots of steep short hills and varying terrain). The G020 has a 45Nm rating where as most mid rives have a rating at least double that. So why not just go with a mid drive? I have some physical limitations that are not compatible with the wider Q required by DIY mid drive kits. I have also ruled out a DD motor due to the added weight. Ideally I would like a geared hub motor that produces closer to 80Nm, lets me use a KT controller, has a cassette body, and still fits in my trikes 135mm rear dropouts. I know Grin has a few premium options but they are out of my price range. Any other other suggestions?

what are your speed requirements, how steep is the grade of the hills, what are the specs of the KT controller and battery, at what speed do you need the extra torque most?

If you have the info, you can model it in the Grin Simulator and make better decisions. If you have the same input power, you may be able to increase torque with some trade offs (e.g. slower winding will have more torque, but lower top speed).

Using the same battery and controller specs in the examples below show a noticeable increase in torque, with the trade off of top speed. If you are willing to go to 52V, you'll have a higher top speed from the slow wind motor, plus even a little more torque at the higher speeds.

Motor Simulator - Web Tools - Resources

Our ebike motor simulator allows you to easily simulate the different performance characteristics of different ebike setups - with a wide selection of hub motors modeled, and the ability to add custom batteries and controllers and set a wide variety of vehicle parameters you'll be able to see...

ebikes.ca

If you need more torque at higher speeds, then you'll likely need to go up in voltage.

 

[lnanek]

Some motors have temperature sensors with an output wire for that, sometimes muxed with the speed wire. Others people add a temperature sensor. Then some controllers like Grin's support thermal throttling based on that. So that's one way to be more sure when going over the stamped wattage.

 

[rocketman58]

I have over 5k miles on the motor. While it has developed a bit of side play it still seems to still work fine. I am not sure the winding of the motor as the Bafang kit makes no mention of this regardless of wheel size. With my 20" wheel the motor makes power up to about 20mph. Assist starts dropping off around 19mph. I seldom travel faster than this, but it would be nice to have a little in reserve. The motor feels pretty strung out at it's top speed.

When I ride with my cycling group we ride a lot of rapidly changing terrain. It is not unusual for me to constantly be selecting a higher assist level while downshifting through the gears at the same time to keep pace as the group rides up a hill. Then having to back off the assist level when descending or reading level ground. Otherwise I am being provided too much assist. I was hoping that having more torque on hand would reduce the need for so much constant adjustments. Maybe this is just the nature of the beast?

I have a 17.5AH battery which will yield me about 60 to almost 70 miles depending on the terrain. The higher the assist level, the less the range. Since I don't ride over 40 mile (don't have the endurance for it) this is not a problem right now. My medical condition will continue to sap my strength as time goes on. Now I am using one higher assist level than I was a year go. This is why I am looking for something with more power.

My current controller is a KT 36/48w - 22a. They do make a KT 36/48w - 25a, recommended for use with a 750w motor. I have also found a 36/48w - 30a controller for use with a 1000w motor. Would using a higher AMP rating controller fry my motor?

 

[neptronix]

You have pedal assist? it sounds like you'd be better off with a throttle.

If you're using PAS, having more torque on hand would mean you need to mess with the power settings more.

 

[ZeroEm]

I have over 5k miles on the motor. While it has developed a bit of side play it still seems to still work fine. I am not sure the winding of the motor as the Bafang kit makes no mention of this regardless of wheel size. With my 20" wheel the motor makes power up to about 20mph. Assist starts dropping off around 19mph. I seldom travel faster than this, but it would be nice to have a little in reserve. The motor feels pretty strung out at it's top speed.

When I ride with my cycling group we ride a lot of rapidly changing terrain. It is not unusual for me to constantly be selecting a higher assist level while downshifting through the gears at the same time to keep pace as the group rides up a hill. Then having to back off the assist level when descending or reading level ground. Otherwise I am being provided too much assist. I was hoping that having more torque on hand would reduce the need for so much constant adjustments. Maybe this is just the nature of the beast?

I have a 17.5AH battery which will yield me about 60 to almost 70 miles depending on the terrain. The higher the assist level, the less the range. Since I don't ride over 40 mile (don't have the endurance for it) this is not a problem right now. My medical condition will continue to sap my strength as time goes on. Now I am using one higher assist level than I was a year go. This is why I am looking for something with more power.

My current controller is a KT 36/48w - 22a. They do make a KT 36/48w - 25a, recommended for use with a 750w motor. I have also found a 36/48w - 30a controller for use with a 1000w motor. Would using a higher AMP rating controller fry my motor?

Used to move my pedal assist up and down, that got old. have a throttle so started using it instead of changing the assist level. Changed my assist ramping where when my pedal speed slows down it ramps up the power. My settings are not aggressive. Used to tweak my settings all the time. More so when I would ride in different terrains.

 

[fill]

If your requiring bursts of extra amps to make up for the current shortfall over the most aggressive terrains, then a 28-30A controller able to satisfy shouldn't result in excessive heat build up in the motor.

But if you need more amps continuously to meet your expectations and dont have an internal motor temperature sensor/readout, it may be more expedient to use the configuration to limit the amp output in 1 amp steps monitoring motor temp in real time as you judge the systems performance. Building up to the output required to avoid overheating.

 

[rocketman58]

The KT controller provide 5 levels of assist. Each assist level provides a certain level of assist up to about 20mph. The controller is not programable other than basic settings accessed from the KT display. I do have a throttle that I use for emergencies such as getting stuck in too high a gear at a stop, or getting out of the way of traffic. It provides full power no matter what assist setting you are in. I have learned how to use the throttle to provide power as gently as possible. I think I could set it to deliver different amounts of power in different assist levels, but that defeats the reason why I have a throttle. I prefer to use cadence sensing instead of a throttle. There might be some settings to adjust the overall assist power. If I remember it is like high, med, low and adjusts all settings a degree higher or lower. I could set this on high which would deliver a small amount of additional power over the factory setting. Something to look into. This still wouldn't address top end speed limitations though.

 

[fill]

Iirc parameter C5 limits the max output of the controller and while a pita moding this in small steps incrementally until the performance required is reached is the safest approach if motor overheating is a risk.

Afaik top end speed (optimum motor rpm) is dependent on the supply voltage, So if your motor isnt able to spin fast enough to maintain a speed required you can consider a higher voltage battery pack if running with a 48v pack a 52v pack (Edit and controller..) should provide you with circa 8-9% extra rpm/speed If you can supply the amps required to reach and maintain that speed over the terrain in question.

 

[E-HP]

The KT controller provide 5 levels of assist. Each assist level provides a certain level of assist up to about 20mph. The controller is not programable other than basic settings accessed from the KT display. I do have a throttle that I use for emergencies such as getting stuck in too high a gear at a stop, or getting out of the way of traffic. It provides full power no matter what assist setting you are in. I have learned how to use the throttle to provide power as gently as possible. I think I could set it to deliver different amounts of power in different assist levels, but that defeats the reason why I have a throttle. I prefer to use cadence sensing instead of a throttle. There might be some settings to adjust the overall assist power. If I remember it is like high, med, low and adjusts all settings a degree higher or lower. I could set this on high which would deliver a small amount of additional power over the factory setting. Something to look into. This still wouldn't address top end speed limitations though.

So you aren’t using imitation torque control mode.which is what makes KT controllers work smoother that other controllers. Most other budget controllers don’t have the option. Speed control mode will give you full power until the bike hits the speed that the throttle position dictates so it won’t feel natural and less controllable. Impossible to have precise throttle control.

 

[rocketman58]

So you aren’t using imitation torque control mode.which is what makes KT controllers work smoother that other controllers. Most other budget controllers don’t have the option. Speed control mode will give you full power until the bike hits the speed that the throttle position dictates so it won’t feel natural and less controllable. Impossible to have precise throttle control.

Is this a setting I can access via the display?

 

[Chalo]

Is this a setting I can access via the display?

Yes. It's in the parameter settings. If you specify which model of display you're using, we can tell you which setting it is and which value you want.

 

[E-HP]

Is this a setting I can access via the display?

It’s P3 on a lot of KT displays. P3=1

 

[rocketman58]

It’s P3 on a lot of KT displays. P3=1

Thanks

 

[rocketman58]

Yes. It's in the parameter settings. If you specify which model of display you're using, we can tell you which setting it is and which value you want.

Thanks