CYC X1 PRO new build

alarum_78

1 µW
Joined
Feb 11, 2021
Messages
1
Hello,

Looking to grab the newest CYC X1 Pro and run the BAC855 at 3000W. I am new to this game but I am not sure if its the best route for me to run a 52v or 72v setup?

I am under the impression higher voltage is ?? better??

Thanks in advance for any insight.
 
alarum_78 said:
Hello,

Looking to grab the newest CYC X1 Pro and run the BAC855 at 3000W. I am new to this game but I am not sure if its the best route for me to run a 52v or 72v setup?

I am under the impression higher voltage is ?? better??

Thanks in advance for any insight.

This is an easy question since the bac855 will never reach 2000w on 52v. Even if it did more rpm/less torque will always be better on your drivetrain. So if you want 3000w (and you do), go 72v.

Btw there is a topic for this motor, no need for new threads.
https://endless-sphere.com/forums/viewtopic.php?f=28&t=95704&start=675
 
Higher voltage is always better, until your controller can't take any more.
 
Tommm said:
alarum_78 said:
Hello,

Looking to grab the newest CYC X1 Pro and run the BAC855 at 3000W. I am new to this game but I am not sure if its the best route for me to run a 52v or 72v setup?

I am under the impression higher voltage is ?? better??

Thanks in advance for any insight.

This is an easy question since the bac855 will never reach 2000w on 52v. Even if it did more rpm/less torque will always be better on your drivetrain. So if you want 3000w (and you do), go 72v.

Btw there is a topic for this motor, no need for new threads.
https://endless-sphere.com/forums/viewtopic.php?f=28&t=95704&start=675

Actually, I do hit 3100 watts peak with the 855 at 52V. But, it only spins the motor at 7000 rpm, so I'm switching to 72V to hit 10,000 rpm. That will allow me to stay in one gear with good chain alignment on the street at any speed I would need.
 
n2mb said:
Tommm said:
alarum_78 said:
Hello,

Looking to grab the newest CYC X1 Pro and run the BAC855 at 3000W. I am new to this game but I am not sure if its the best route for me to run a 52v or 72v setup?

I am under the impression higher voltage is ?? better??

Thanks in advance for any insight.

This is an easy question since the bac855 will never reach 2000w on 52v. Even if it did more rpm/less torque will always be better on your drivetrain. So if you want 3000w (and you do), go 72v.

Btw there is a topic for this motor, no need for new threads.
https://endless-sphere.com/forums/viewtopic.php?f=28&t=95704&start=675

Actually, I do hit 3100 watts peak with the 855 at 52V. But, it only spins the motor at 7000 rpm, so I'm switching to 72V to hit 10,000 rpm. That will allow me to stay in one gear with good chain alignment on the street at any speed I would need.

Ok, the bac controllers are power limited, on lower volts they will get you more battery amps, I wasn't sure of that, anyway, you won't get more power from it, yes the motor will spin faster, but getting a new battery is the single most expensive thing you can do to fix your issue.

The torque curve won't change at all, an 52v battery running at 3000w will be undiscernible from a 72v one at 3000w if the gearing difference is accounted for, you won't be able to keep it in a gear longer.

If both systems top out at 3000w, and:
If you are in a gear with a 20mph top speed with 52v battery
It is true that gear will give 30mph top speed with 72v battery
But if you switch to a gear with 30mph top speed on 52v battery, the acceleration, top speed, everything will be the same as if you were running on a 72v battery that also maxes out at 3000w.

If chain alignment is your issue it is a whole different discussion, or if you want to use a bigger rear cog that is a separate issue, but swapping batteries to fix something that can be done for $10, doesn't make sense.

To fix chain alignment: Put a small cog (smallest or one before the smallest one) behind the big cog of your cassette, it will bring all your gears outwards by 1 gear and spacer width. If you are willing to sacrifice more gears, you can buy a "single speed conversion kit" on ebay, they will provide you with ample amount of spacers you can use to get rid of 3-4 cogs even, and shuffle the big cogs in the middle.

To be able to use higher teeth cont rear gears at lower speeds:
You can get a bigger motor cog (12t)
Smaller front motor cog (219h 63t or 53t vs 72t)
Get a bigger bike chainring 36-38 should fit on anything, sometimes up to 44t.
 
I'm not so sure about that. The torque is limited by phase amps, not by power. So, if I switch to a faster gear and stay at 52V, I get really low torque, since the phase amps are still limited to 100 amps, which directly determines motor torque. If I could increase phase amps, then I agree with you, I would get the same performance at 52V as at 72V.

So, switching to 72V, I should be able to maintain the same phase amp limit until a higher RPM, translating to more usable speed in a gear with lots of torque. Once it is power limited by the controller, then the acceleration will be the same.
 
Tommm said:
Ok, the bac controllers are power limited, on lower volts they will get you more battery amps, I wasn't sure of that, anyway, you won't get more power from it, yes the motor will spin faster, but getting a new battery is the single most expensive thing you can do to fix your issue.

The torque curve won't change at all, an 52v battery running at 3000w will be undiscernible from a 72v one at 3000w if the gearing difference is accounted for, you won't be able to keep it in a gear longer.

If both systems top out at 3000w, and:
If you are in a gear with a 20mph top speed with 52v battery
It is true that gear will give 30mph top speed with 72v battery
But if you switch to a gear with 30mph top speed on 52v battery, the acceleration, top speed, everything will be the same as if you were running on a 72v battery that also maxes out at 3000w.

If chain alignment is your issue it is a whole different discussion, or if you want to use a bigger rear cog that is a separate issue, but swapping batteries to fix something that can be done for $10, doesn't make sense.

To fix chain alignment: Put a small cog (smallest or one before the smallest one) behind the big cog of your cassette, it will bring all your gears outwards by 1 gear and spacer width. If you are willing to sacrifice more gears, you can buy a "single speed conversion kit" on ebay, they will provide you with ample amount of spacers you can use to get rid of 3-4 cogs even, and shuffle the big cogs in the middle.

To be able to use higher teeth cont rear gears at lower speeds:
You can get a bigger motor cog (12t)
Smaller front motor cog (219h 63t or 53t vs 72t)
Get a bigger bike chainring 36-38 should fit on anything, sometimes up to 44t.

This is not correct.
The controller is not power-limited; lower volts will not get you more battery amps. Current is limited to 90A within the input voltage range. At 90A peak, 52V = 4680W, 72V = 6480W, subject to thermal cutback.

Adding battery is also the single most effective thing you can do to improve an ebike.

Since motor torque is limited by controller current, adding battery voltage and thus motor rpm allows more torque multiplication gearing for the same final speed.
 
fatty said:
This is not correct.
The controller is not power-limited; lower volts will not get you more battery amps. Current is limited to 90A within the input voltage range. At 90A, 52V = 4680W, 72V = 6480W, subject to thermal cutback.

Adding battery is also the single most effective thing you can do to improve an ebike.

Since motor torque is limited by controller current, adding battery voltage and thus motor rpm allows more gearing torque multiplication for the same final speed.

Hm, I haven't came close to getting near whatever power limit the bac2000 would have, so I don't have first hand experience, but it is confusing, I've seen multiple people claim they get 3000w from a bac855 on a 52v battery, that is only possible if it is power limited, as 3000w on 52v would mean with the same battery amps 5000w on 72v and we know it can't do that.
 
fatty said:
This is not correct.
The controller is not power-limited; lower volts will not get you more battery amps. Current is limited to 90A within the input voltage range. At 90A, 52V = 4680W, 72V = 6480W, subject to thermal cutback.

Adding battery is also the single most effective thing you can do to improve an ebike.

Since motor torque is limited by controller current, adding battery voltage and thus motor rpm allows more gearing torque multiplication for the same final speed.

It's also limited by phase amps. I have it set to 100 amps, which is already over the spec limit of 90 amps. That seems to be the bigger limit at 52v. It stays pegged at 100 motor amps for quite some time during acceleration. It briefly hits 3kW, but then the power starts tapering off as the motor RPM rises too high and the back EMF makes it impossible for the 52V battery to supply enough current.

Here's an example pull. Battery power on the left in watts, motor current and battery current on the right.
https://www.dropbox.com/s/oktg3vz0c4i1d5d/Screenshot%202021-01-15%20095029.png?dl=0
 
Tommm said:
Hm, I haven't came close to getting near whatever power limit the bac2000 would have, so I don't have first hand experience, but it is confusing, I've seen multiple people claim they get 3000w from a bac855 on a 52v battery, that is only possible if it is power limited, as 3000w on 52v would mean with the same battery amps 5000w on 72v and we know it can't do that.

Well, ASI does not specify power limits, only phase current limits (attached). You're right that those theoretical watts will never be reached -- I was just trying to illustrate that higher system volts at the same phase current equals higher motor power.
 

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n2mb said:
It's also limited by phase amps. I have it set to 100 amps, which is already over the spec limit of 90 amps... It stays pegged at 100 motor amps for quite some time during acceleration.

Yeah, I was referencing the 90A phase current limit -- sorry that was unclear though.
But interesting you're able to set the phase amps higher than spec. Since the controller has thermal cutback, I wonder how much higher can it go?


n2mb said:
It briefly hits 3kW, but then the power starts tapering off as the motor RPM rises too high and the back EMF makes it impossible for the 52V battery to supply enough current.

This isn't a battery current limit though, or else you'd trip the BMS overcurrent protection and power would cut completely.
The battery current could be infinite and you would see the same behavior. You can test this by artificially limiting controller battery current.
 
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