Bosch CX 4
The "endurance runner" of the E-MTB world. Since its introduction (2019, Smart System from 2021), the Bosch CX Gen 4 has been the top dog in the sporty E-Bike and E-MTB sector. With 85 Nm of torque and its "Extended Boost," it offers excellent modulation in technical uphills. Technically, it is based on a 36-volt system. Even though it is being successively replaced by the Gen 5 starting in 2025, it remains relevant due to its enormous market penetration and spare parts availability. In autumn 2025, it received the new eMTB+ mode via an update. The only point of criticism was always the mechanical rattling in the freewheel during descents.
Battery System & Chargers
🔋 Battery System
| Model | Capacity | Weight | Energy Density | Dimensions | Mounting |
|---|---|---|---|---|---|
| Powertube 800 | 800 Wh | 3.9 kg | 205 Wh/kg | 424 x 77 x 71 | Internal |
| Powertube 750 | 750 Wh | 4.3 kg | 174 Wh/kg | 484 x 84 x 65 | Internal |
| Powertube 625 | 625 Wh | 3.6 kg | 174 Wh/kg | 415 x 84 x 65 | Internal |
| Powertube 600 | 600 Wh | 3 kg | 200 Wh/kg | 424 x 71 x 67 | Internal |
| Powertube 540 | 540 Wh | 3 kg | 180 Wh/kg | 424 x 71 x 67 | Internal |
| Powertube 500 | 500 Wh | 3 kg | 167 Wh/kg | 345 x 84 x 65 | Internal |
| Compactube 400 | 400 Wh | 2 kg | 200 Wh/kg | 352 x 57 x 75 | Internal |
| Powerpack 800 Frame | 800 Wh | 3.9 kg | 205 Wh/kg | 345 x 95 x 100 | Frame |
| Powerpack 545 Frame | 545 Wh | 3 kg | 182 Wh/kg | 338 x 93 x 81 | Frame |
| Powerpack 400 Frame | 400 Wh | 2.2 kg | 182 Wh/kg | 336 x 91 x 62 | Frame |
| Powerpack 500 Rack | 500 Wh | 2.8 kg | 179 Wh/kg | 376 x 122 x 64 | Rack |
| Powerpack 400 Rack | 400 Wh | 2.7 kg | 148 Wh/kg | 376 x 122 x 64 | Rack |
➕ Range Extender Available
| Model | Capacity | Weight | Dimensions |
|---|---|---|---|
| Powermore 250 | 250 Wh | 1.5 kg | 200 x 88 x 75 |
🔌 Chargers
| Model | Current | Dimensions |
|---|---|---|
| Standard Charger | 4 A | 201 x 90 x 53 |
| Compact Charger | 2 A | 167 x 76 x 45 |
Power Characteristics
Shows how much power the motor delivers for a given rider input. The value shown is pure motor power, adjusted for input and drivetrain losses.
Input vs. Output: Bosch CX 4
The 4th generation Bosch CX motor shows a thoroughly sporty response. To call up the maximum output of around 540 watts, almost 180 watts of power are required from the rider. Apart from that, the drive shines with a power delivery that is inconspicuous in a positive sense. A good choice for those who don't shy away from pedaling hard themselves for high motor performance. Those who prefer to be pulled up the mountain without much effort will find other systems more suitable.
Cadence Behavior
Shows the optimal RPM range.
RPM: Bosch CX 4
The motor's power delivery across the cadence spectrum between 30 and 120 is absolutely flawless. You get plenty of power even at around 50 rpm—ideal for those who don't like riding in easy gears. But almost more impressive is the consistent power delivery up to 120 rpm (and beyond). We record hardly any fluctuation here. Hardly any other drive manufacturer can keep up in this regard.
Thermal Performance
Shows power output performance over 15/20 minutes under constant full load.
15 min
Up to the 10-minute mark, the Bosch CX Gen 4 can hold its full power, then we see a gentle derating and a steady, slight loss of power. The housing temperature here is around 80°C. Due to the very slow power loss, this is hardly noticeable in practice, but that doesn't change the fact that other motors hold out longer here.