Does anyone know how many Ampere the controller on the Bosch CX 4.gen draws at max? The motor is nominally 250 watts, but I would like to know what the maximum watts are. When you know the maximum Ampere, I think you can also calculate how many watts the motor can produce with a full and nearly empty battery. (AxV=Watt-max)
Bosch CX controller, Amp
- Thread starter Elsyklist
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fooferdoggie
Well-Known Member
Bosch does not give you peak watts unless you're using turbo you won't see sag in motor power when the battery is about drained.
I do know it takes putting out around 520 watts to hit the peak of my gen4 speed motor.
I do know it takes putting out around 520 watts to hit the peak of my gen4 speed motor.
Ok, I think I can tell the difference between an almost empty battery and a full one when I switch to a spare battery on long trips. But the reason I'm asking about this is discussions around 250, 500 and 750 watt motors on a FB group. My 250 watt rated motor certainly has a much higher maximum wattage. And if I only knew how many amps the controller allows, I could calculate this exactly.
fooferdoggie
Well-Known Member
How much the motor puts out peak and continuous are different. i have put out 700 watts when feeling good for a few seconds and the motor still gave me power. but climbing a steep hill me putting out 520 watts is about where the motor cuts off.
Sparky731
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- USA
You posit an interesting computation, but I lean toward knowing this as either a moot consideration or over-analysis. I ride a Bosch Speed 250w motor so can’t totally vouch for a CX.
But I will vouch for a very steady electron production without noticeable power delivery variance at 100%, 50% or even 10% of electron storage. If that is what you are asking. That’s the Bosch storage management system.
I ride primarily Turbo and generally zoom along at 24-27mph. 625w RIB + 500w Power Extender gives me ~60 miles, (265 miles in Eco) but I have no idea how to calculate my power utilization.
But I will vouch for a very steady electron production without noticeable power delivery variance at 100%, 50% or even 10% of electron storage. If that is what you are asking. That’s the Bosch storage management system.
I ride primarily Turbo and generally zoom along at 24-27mph. 625w RIB + 500w Power Extender gives me ~60 miles, (265 miles in Eco) but I have no idea how to calculate my power utilization.
Stefan Mikes
Gravel e-biker
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- Europe
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- Mazovia, PL
The knowledge of the max amperage will not help you if you do not know the motor efficiency (to calculate the mechanical power based on the electrical draw of the current from the battery).
Given the 85 Nm max of the CX motor, assume the Peak Mechanical Motor Power of around 520 W. (I know the specs and measurement for similar motors from two other brands).
Yes, it is complicated and it is a problem that Bosch is so unwilling to share information. But the kind of information I'm looking for exists for other brands. For example here: https://ebikes.ca/tools/simulator.h...hp=300&cont=C25&batt=B3617_35E&motor=MG01_FST
Maybe someone has an idea as to which of the stated motors is most similar to Bosch CX?
Also note that if you switch controls, the red curve will also change quite significantly if you go from 20 to 25A. This is related to my original post. But of course it is not as simple as A times V equals W. The controller also has other ways of regulating the engine's performance.
Maybe someone has an idea as to which of the stated motors is most similar to Bosch CX?
Also note that if you switch controls, the red curve will also change quite significantly if you go from 20 to 25A. This is related to my original post. But of course it is not as simple as A times V equals W. The controller also has other ways of regulating the engine's performance.
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Stefan Mikes
Gravel e-biker
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None.
I was comparing the CX to Specialized 1.2s (Brose TF) and Giant Syncdrive Pro (Yamaha PW-X2) that offer similar torque but the max mechanical motor power has been published. Measurements on the 1.2s allow stating that the maximum electrical power draw for that motor is around 660 W translated to 520 W mechanical at efficiency of 0.78.
fooferdoggie
Well-Known Member
the max torque also depends on your torque and your cadence too.
Sparky731
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- USA
So if we can draw 520 watts of electrons into the motor from a 500w battery, it would seem as though the battery either cannot meet that demand, or it will expunge its electrons very quickly indeed, hence the need for 625w or more if you enjoy the rush being a speedy rider. I do.
Stefan Mikes
Gravel e-biker
- Region
- Europe
- City
- Mazovia, PL
You completely miss the difference between Power (expressed in W) and the amount of the energy stored in the battery (Wh) -- other names for the latter being battery charge or battery capacity. If you draw 500 W of power from a 500 Wh battery, it will take an hour to totally discharge the battery.
Sparky731
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When I decided to ride only Turbo, I quickly realized that I also needed to add more electrons. And Lithium is not cheap.
I took an extra breath when I read Bosch’s performance graphs identifying how few extra miles I would get out of their 500w Range Extender battery. It is like 25 miles.
But I was also not able to complete my daily circuit with the original 500w RIB, and what a pisser it is to ride in Eco to get home.
If you want to ride fast while pushing your bike to its limits ya gotta make choices. I put away my calculator and bought more Lithium. Can’t have enough.
I took an extra breath when I read Bosch’s performance graphs identifying how few extra miles I would get out of their 500w Range Extender battery. It is like 25 miles.
But I was also not able to complete my daily circuit with the original 500w RIB, and what a pisser it is to ride in Eco to get home.
If you want to ride fast while pushing your bike to its limits ya gotta make choices. I put away my calculator and bought more Lithium. Can’t have enough.
Sparky731
Well-Known Member
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- USA
It will also run my refrigerator.
Sparky731
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- USA
I go back to amperage draw, which is the hidden variable within the equation. The best I can do is a factor for Amps, i.e., relatively speaking, Turbo draws electrons (amperage) at 4x Eco. Purion is not very forthcoming with its data.
Stefan Mikes
Gravel e-biker
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- Europe
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- Mazovia, PL
Yes but it works as follows:
What a mid-drive system actually does is multiplying your feet torque by your cadence (I'm simplifying things here). What the e-bike control unit gets is your leg power. Then your leg power is multiplied by the Boost Factor, which is 4x on the most powerful Bosch motors in Turbo mode. If you can input 520/4 = 130 W with your legs (which is easy), Bosch CX motor will respond with 520 W of mechanical assistance in Turbo. If you pedal stronger, the motor will remain maxed out at 520 W.
Bosch and other Euro focused manufacturers give Torque as they do not want to reveal their motors are actually stronger than 250 W (nominal). Torque is safe information to be revealed.
wildtrak
Active Member
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- Morgan Hill
I can easily drain a 500Wh battery in 40 minutes, going full speed in headwind in Turbo.
That would be 750Wh in one hour which equals a power of 750W continuously over one hour (or 750W in 2/3 of an hour (40 minutes) equals 500Wh).
So does that mean the motor does 750W while riding on maximum power?
No, it does not.
But that is what you get when you just look at the Amps and Volts (Watts) of the battery output.
That is why I don't even care and just ride and switch batteries when there is no more juice in them. I actually don't switch that much as I have dual battery setup on all my bikes and even a 1kWh (=1,000Wh) battery with a Bosch BMS (6P10S 21700s). 1,500Wh takes me really far before I have to switch a battery.
But for my 35 miles roundtrip to the gym and back several times a week, the two 500Wh batteries are just enough. The headwind is draining them really fast, so can only do one way in Turbo and one way in Sport as I need some juice at the end to get up that hill back home.
That would be 750Wh in one hour which equals a power of 750W continuously over one hour (or 750W in 2/3 of an hour (40 minutes) equals 500Wh).
So does that mean the motor does 750W while riding on maximum power?
No, it does not.
But that is what you get when you just look at the Amps and Volts (Watts) of the battery output.
That is why I don't even care and just ride and switch batteries when there is no more juice in them. I actually don't switch that much as I have dual battery setup on all my bikes and even a 1kWh (=1,000Wh) battery with a Bosch BMS (6P10S 21700s). 1,500Wh takes me really far before I have to switch a battery.
But for my 35 miles roundtrip to the gym and back several times a week, the two 500Wh batteries are just enough. The headwind is draining them really fast, so can only do one way in Turbo and one way in Sport as I need some juice at the end to get up that hill back home.
fooferdoggie
Well-Known Member
wildtrak
Active Member
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- USA
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- Morgan Hill
@fooferdoggie yes, more than enough to max out the motor assistance.
fooferdoggie
Well-Known Member
I mean do you have a number?
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