Bosch Performance CX Gen 4 nominal power

[Hall]

This is a bit theoretic question or thought:

Am I correct saying that IF Bosch Performance CX Gen 4 is restricted to have 250w nominal power, THEN it has to limit output power at some level?
For example if I (theoreticalyl) ride at the maximum wattage (600w) full hour, the motor can't have the full 60min the full power?

I ended up thinking this when I was riding full day and the turbomode didn't feel as powerful as it was at the morning. There could be also some temperature limitations to protect the engine OR/AND some relation to BMS trying to save energy.

What do you think?

 

[retiredNH]

I find that with my rides, the motor always seems less powerful toward the end of the ride.

I do think your question is a good one though, since I find that my bike pulls up the steepest hills around quite well.

 

[Dallant]

Not sure but my normal workout rides of 20-27 miles always end with the last mile or two going up three very steep hills with EMTB or Turbo mode. My Allant+7 with the CX seems just as strong going home as it was going up these same hills on the ride out. If you have the latest update, EMTB is a variable power mode that CAN get up to Turbo’s 340% assistance, so it’s hard to know exactly whats happening.

 

[triplemaya]

Voltage will fall as you use the battery. fully charged a 36v battery puts out 42 volts. It will go down to around 30v before it cuts out. And the voltage drops off a lot faster as the pack nears empty, last 10% or so it really plummets. hth

 

[fooferdoggie]

with my performance motors I don't notice any change until the battery cuts out. but I am not pushing hard at the time usually too.

 

[retiredNH]

Voltage will fall as you use the battery. fully charged a 36v battery puts out 42 volts. It will go down to around 30v before it cuts out. And the voltage drops off a lot faster as the pack nears empty, last 10% or so it really plummets. hth

Without knowing the design of the motor controls, we don't know if this is an issue or not. For example, if the controller uses current regulation, even the lower voltage may be enough to provide adequate current for a particular power setting.

 

[triplemaya]

Without knowing the design of the motor controls, we don't know if this is an issue or not. For example, if the controller uses current regulation, even the lower voltage may be enough to provide adequate current for a particular power setting.

It sounded like the op was wanting full power. Full power must drop as the voltage falls. Watts [power] = Volts x Amps.

 

[fooferdoggie]

Without knowing the design of the motor controls, we don't know if this is an issue or not. For example, if the controller uses current regulation, even the lower voltage may be enough to provide adequate current for a particular power setting.

it usually is with a Bosch system you don't get that power drop like you usually do. IA sure the other brands like specialized and such have it too.

 

[Dallant]

Voltage will fall as you use the battery. fully charged a 36v battery puts out 42 volts. It will go down to around 30v before it cuts out. And the voltage drops off a lot faster as the pack nears empty, last 10% or so it really plummets. hth

I always have 50-60% left when I get home from a full 27 mile ride.

 

[retiredNH]

It sounded like the op was wanting full power. Full power must drop as the voltage falls. Watts [power] = Volts x Amps.

But in a current regulated system, the voltage will be modulated, and will usually be lower than the supply voltage. Systems are often designed this way precisely to avoid the problem of power sag as the supply voltage drops. And modern controls are one reason modern AC drive motors are so much better than the old true DC motors.

 

[BlackHand]

This is a bit theoretic question or thought:

Am I correct saying that IF Bosch Performance CX Gen 4 is restricted to have 250w nominal power, THEN it has to limit output power at some level?
For example if I (theoreticalyl) ride at the maximum wattage (600w) full hour, the motor can't have the full 60min the full power?

I ended up thinking this when I was riding full day and the turbomode didn't feel as powerful as it was at the morning. There could be also some temperature limitations to protect the engine OR/AND some relation to BMS trying to save energy.

What do you think?

Yes, there are limits in the total power output to comply with EU regs. But you are also likely experiencing battery and muscle sag if you are comparing fresh battery and legs to depleted battery and legs at the end of the day.

has a maximum continuous rated power which does not exceed 250 watts;”; and Regulation (EU) No 168/2013 defines “maximum continuous rated power” as the maximum thirty minutes power at the output shaft of an electric engine as set out in United Nations Economic Commission for Europe (UNECE) regulation No 85.

 

[Hall]

Yes, there are limits in the total power output to comply with EU regs. But you are also likely experiencing battery and muscle sag if you are comparing fresh battery and legs to depleted battery and legs at the end of the day.

has a maximum continuous rated power which does not exceed 250 watts;”; and Regulation (EU) No 168/2013 defines “maximum continuous rated power” as the maximum thirty minutes power at the output shaft of an electric engine as set out in United Nations Economic Commission for Europe (UNECE) regulation No 85.

Yes. The bold text was my base hypotesis for guessing if Bosch's motor has some kind of function to adjust power to meet the requirement.

When running turbo, there's no effect on muscle sag.

What I'm saying: It can't be possible to have 30min 600w, because it would be against EU regulations. Therefore there must be some way to measure and adjust/restrict output power to stay under the nominal power limit.

 

[BlackHand]

Sure, but I doubt anyone but some Bosch engineers know what the algorithm or sampling times are that the BMS uses to regulate total power output (in addition to temp, cadence, assist setting, torque and voltage that all factor in).

I guess if you hooked a bike up to an indoor trainer you might be able to pedal long and steady enough to get an idea how long it will maintain peak power.

 

[Hall]

Someone should really do a brake dynamometer for the motors and artificially measure the power.

I wonder who and how makes the tests for all of the motors to ensure that they meet the regulations.

 

[retiredNH]

I wonder who and how makes the tests for all of the motors to ensure that they meet the regulations.

Volkswagon?

 

[webcurl]

Battery age/cycles a factor?

 

[Hall]

Battery age/cycles a factor?

It's definitely a factor but the fulfillment of the 250w requirement can't be relied on that because it has work when the bike is new.