Nice Feature on a Hub Drive

[gromike]

I read about this feature before that's on the Grin controller installed on my direct-drive hub motor ebike.
Today, I used the feature.
When you go to assist level 0 the controller gives the motor a watt of power, and the wheel rolls without the magnets causing cogging resistance. Which means the bicycle has no motor drag. The bike pedals like a normal bike, albeit a heavy one. With the controller turned off, it's like pedaling through thick molasses.
This insight is due to my new ebike adventure -- traveling at the lowest assist level I can get away with.

 

[Chargeride]

The drag, I guess its normally just turning into heat?

 

[Slaphappygamer]

Glad to hear more about how that works. I’ve got a Baserunner and CA3 on the way. I’m excited to check out all the features, except regen. I don’t have a DD.

It’s also nice to have that watt of power for the motor to always be engaged and using the throttle won’t startle the motor.

 

[PCeBiker]

I’m excited to check out all the features, except regen. I don’t have a DD.

You can open up your motor and disable the clutch.
Then you'll have a regenerating geared hub motor.

Might be hard on your gears though, but I figure that's only if you crank your regeneration to max.

Grin allows you to twist your throttle backwards to increase the amount of regeneration power. (KT just offers a few choices.)

And be careful not to blow up a fully charged battery.
I don't know how Grin deals with that?
Perhaps regeneration won't work until your battery voltage drops to a certain level?

Then you might need an expensive new battery that can charge and discharge at up to 100 amps if you max out your regeneration.

I can't squawk my tire with 20 amps thrown at it, so it would take A LOT more regeneration amps before I'd lock up my tire.

 

[PCeBiker]

The drag, I guess its normally just turning into heat?

That's what I figure, but some of that energy is turned into mechanical vibration before it turns into heat, and that vibration can damage mechanical and electrical things.

 

[Bella-Motor-HP]

As long as the cells in the battery are decent cells you would not need a new battery.
You need to find specifications for the battery cells in your pack to find out how many amps discharge / charge they can each take.
Then just get a good BMS.
A BMS that can use the full power of the battery cells you have.

Like for instance my UPP 48V 24AH battery has LG INR2170-M50L Cells in it.
So looking at LG Specs.

https://www.dnkpower.com/wp-content/uploads/2019/02/LG-INR21700-M50-Datasheet.pdf

My battery is 13S-5P
DISCHARGE AMPS MAX = 7.275 amps per cell pack (P)
5 Parallel Packs X 7.275 amps = 36.375 amps for my pack <<<---Recommended Level

5 Parallel Packs X 14.550 amps = 72.75 amps for my pack @ optimal temperature. <<<--- if you can maintain the Battery temp below 77 deg F (You can double output)
If you run hotter than 77 then you set the BMS to cut back amps in relationship to the battery temp.

5 Parallel packs @ Mean @ Optimal Temp = (((72.75-36.375)/2)+36.375)=54.5625 Mean Discharge Amps

60 Amp BMS would be ok. Leaves 12 amps to spare to max current. Note That BMS outputs more than 60 AMPS

So my battery comes from the factory with a 40A BMS.
I could run a 60A BMS or run even a Bigger BMS and then limit the current using the controller settings.

So no need for a new battery. If yours has decent cells. It's not real difficult to change the BMS.

 

[PCeBiker]

When you go to assist level 0 the controller gives the motor a watt of power, and the wheel rolls without the magnets causing cogging resistance.

@gromike
I assume that you use regenerative braking?

What happens if you start with a fully charged battery, and you live on top of a mountain, then use regenerative braking going down the mountain?

Does the braking work?
Could it overcharge the battery and set it on fire??
I would think that the BMS would prevent an overcharge, but that energy has to go somewhere?

I know Grin must have done something to deal with that.

 

[Slaphappygamer]

The BaseRunner can be set to stop accepting regen at a particular voltage level. In the phaserunner suite, you can set the voltage level that regen kicks in and the level in which regen voltage stops flowing to the battery. This will avoid over-charging the battery.

I’ll be adding a temp sensor to my motor. I’ll see what the clutch looks like while I’m in there. Since I would only travel 8 miles in a day, I’m not too interested in having regen. Still, I’m curious what it would entail. I know I can weld the clutch, but I don’t know how to weld. I figure I’ll use this motor till the bitter end, then I may upgrade to a DD.

 

[Bella-Motor-HP]

Basically the BMS will shut off the power on a overcharge condition. The VESC also will do the same thing. You can program them both to shut off at a given AMP output to protect the battery and motor. Also you set the maximum charge voltage and if it goes or tries to go higher it will shut off the BMS or VESC. As far as the hill and regen on a full charge, it's not good. It will try to overcharge the battery but the BMS will shut off. So simply don't charge the battery all the way to the top. Leave 2% or some small amount for that initial regen. You can set a timer to shut off the battery charger before the battery is full. Or set the BMS to charge less than full. Then when your done charging set the BMS back to the normal V. That is a easy way to deal with it. You need a bluetooth BMS like this.

Amazon.com

Then you have control of all the settings.

Also as far as the clutch goes I plan to machine some solid clutches with upgraded gears.

 

[PCeBiker]

,.. Since I would only travel 8 miles in a day, I’m not too interested in having regen.

And even the guy from Grin says that the most you can hope for is around 10% further range.

I wonder why it's so inefficient?

I can head into the wind and use over 450 Watts, then I turn around and use less than 150 Watts with a tailwind.
I'm sure that's more than 10% so why is using a hill so different?

 

[PCeBiker]

The BaseRunner can be set to stop accepting regen at a particular voltage level.

Basically the BMS will shut off the power on a overcharge condition.

So what happens when the BMS shuts you down?

I would think that when the regeneration stops, your braking force would too?

Or does the whole ebike just shut down like when you hit LVC?

 

[Slaphappygamer]

I think this could answer those questions. I can not. Grab your Vado and coffee.

 

[mschwett]

And even the guy from Grin says that the most you can hope for is around 10% further range.

I wonder why it's so inefficient?

I can head into the wind and use over 450 Watts, then I turn around and use less than 150 Watts with a tailwind.
I'm sure that's more than 10% so why is using a hill so different?

mostly because people don’t ride bikes slow enough downhill to really generate such a big surplus. most of the energy is still lost to air resistance.

if you ride an e-bike up a really steep, long hill at 10mph using a couple hundred watts… and then turn around and come down, to regain most of that power you’d have to to descend at 10mph (actually slightly less) to regain anywhere near the amount of energy you put into climbing the hill. if you descend at 30mph, the vast majority of the potential energy you banked by going up is given back to overcome the wind resistance of going 30mph.

it’s just no fun riding downhill slow enough to really recapture that energy.

 

[Bella-Motor-HP]

So what happens when the BMS shuts you down?

I would think that when the regeneration stops, your braking force would too?

Or does the whole ebike just shut down like when you hit LVC?

Yea I'm pretty sure it just cuts the current off.
And yes you would loose brake.
I'm gonna end up running regen braking and my front disk brake.
I'm gonna end up loosing my rear disk.
Got to make room for 8GA phase leads and cooling lines.
So like I said, you either charge the battery full then lift the wheel of the ground and spin it for a min to drop a little V. Or you use a BMS to set the charge voltage. Some batterie cells can actually take higher than charge voltage. To some degree. If you look at the specs I posted above it shows the V and current they push through a cell to test it. They can go a lot higher. But you will loose life.

 

[m@Robertson]

When you go to assist level 0 the controller gives the motor a watt of power, and the wheel rolls without the magnets causing cogging resistance. Which means the bicycle has no motor drag. The bike pedals like a normal bike, albeit a heavy one.

That sounds like it would solve one of the major negatives with regard to using regen on a DD hub system: You can never just coast and take advantage of the momentum you have earned on a regen-enabled DD system. Like you would if you are riding in town and you can see a light turn red a half block ahead. With this feature you could just ghost-pedal, slowly, which keeps PAS enabled and thus fails to trigger the drag of regen. Thats damn clever.

 

[Bella-Motor-HP]

Im thinking of doing the same as the phaserunner.
We can code into the VESC and program it to give us the freewheel effect.

I am also going to use a Flipsky Remote for a skateboard that has forward and reverse built into the throttle. The forward motion of the Throttle will control the level of regen breaking. It probably won't mount to my handlebar the way I want out of the box so either I will remove the guts and put them in my own shell or simply make a mount to mount it.

Secondly you set the VESC for the amount of regen current you want to allow back to the battery. And then on top of that program the BMS to only allow certin level of charge current.

Far as PAS we can hook that up as a secondary throttle input. It works the same way. The big difference is with the VESC we can map and adjust the throttle levels. Meaning we can make the motor react to the throttle / pas any way we wish.

We can fine tune every parameter the way we wish.

Also the Eggrider works with the VESC. I have a EggRider hoked up. But you can just use the VESC Bluetooth app on your phone for a really good display.

All this stuff is open source. Meaning if it won't do what you want you can simply write your own code and implement your own features. So the only limitation is how creative you can be.

 

[PCeBiker]

When you go to assist level 0 the controller gives the motor a watt of power,

You can never just coast and take advantage of the momentum you have earned

On a related note, @m@Robertson mentioned that the KT controller never drops to zero Watts while coasting.
I finally had a long enough downhill coast for the KT Watt meter to read its lowest reading and I was something like 20 Watts.

So I guess it takes more power to overcome the drag of my clutch, than it takes to overcome the cogging resistance of a DD?

Does that make sense?

 

[Bella-Motor-HP]

It is the force of wind resistance that influences the power level. The wind resistance is adding way more drag than the motor in either case.

 

[m@Robertson]

On a related note, @m@Robertson mentioned that the KT controller never drops to zero Watts while coasting.
I finally had a long enough downhill coast for the KT Watt meter to read its lowest reading and I was something like 20 Watts.

I can get a different minimum number if I re-grease the hub (goes down), or I clamp it back together a little wrong. If I do a re-grease and the minimum jumps to 60w then I know I've done something wrong and have to go back over it again. Thats actually happened to me.

 

[PCeBiker]

I can get a different minimum number if I re-grease the hub (goes down), or I clamp it back together a little wrong. If I do a re-grease and the minimum jumps to 60w then I know I've done something wrong and have to go back over it again. Thats actually happened to me.

COOL That makes sense !!

The controller probably compares the speed sensor data to the hall sensor data to know how much power to give the motor to overcome the drag of the clutch and/or grease.