| 48KG·CM STALL | 0.106S/60° NO-LOAD | 8.4V RATED |
| 73G WEIGHT | StainlessGEARTRAIN | 360°TRAVELCustomizable |
Overview
The BLS8145D is the 48 kg·cm member of the standard-size brushless family: 20 × 40 × 38.4 mm case, 73 g, and 0.106 s/60° at 8.4 V. It is the highest-torque servo in this footprint short of stepping up to the 30 V industrial line.
The case is CNC aluminium with the fins milled into the sides, the geartrain is stainless steel on two ball bearings, and the output is a 25T-φ5.94 mm spline with a POM horn. Mechanical limit 210°, dead band 1 µs, lead 300 mm.
This page covers the RS-485 build: the same mechanics, commanded over a differential serial bus instead of a PWM channel. It is the version to pick when several servos sit on one pair of wires or when the cable run is long enough that a single-ended signal would pick up noise.
Performance at each supply voltage
| Supply | No-load speed | Peak stall torque | Idle current | Stall current |
|---|---|---|---|---|
| 6.0 V | 0.144 s/60° (417 °/s) | 37 kg·cm (3.63 N·m / 514 oz·in) | 320 mA | 3.7 A |
| 7.4 V | 0.122 s/60° (492 °/s) | 43 kg·cm (4.22 N·m / 597 oz·in) | 370 mA | 4.5 A |
| 8.4 V | 0.106 s/60° (566 °/s) | 48 kg·cm (4.71 N·m / 667 oz·in) | 440 mA | 5.2 A |
Control specification
| Item | Specification |
|---|---|
| Command signal | RS-485 |
| Amplifier | Digital controller |
| Dead band | 1 µs |
| Rotating direction | CCW (1000–2000 µs) |
| Travel | 360°, customizable |
Mechanical specification
| Item | Specification | Item | Specification |
|---|---|---|---|
| Dimensions | 20 × 40 × 38.4 mm | Case material | Aluminium, CNC |
| Weight | 73 g | Geartrain | Stainless steel |
| Bearings | 2 × ball bearing | Motor | Brushless |
| Output spline | 25T-φ5.94 mm | Horn | Plastic, POM |
| Lead / connector | 300 mm, 3-wire | Mechanical limit | 210° |
| Operating temperature | −15 °C to 65 °C | Storage temperature | −20 °C to 70 °C |
| Ingress protection | Splash resistant (customizable) | Travel | 360°, customizable |
What’s in the box
- 1 × XQ-RS8145D servo
- 1 × POM horn set
- 1 × mounting screw pack
Optional: metal horn, sold separately.
How to size it
Torque is 37 kg·cm at 6.0 V, 43 at 7.4 V and 48 at 8.4 V, at 0.144, 0.122 and 0.106 s/60°. Even on a tired 2S pack this is a 43 kg·cm servo, which is why it is the usual choice where a 35 kg·cm model was marginal.
Stall current is 5.2 A at 8.4 V against 440 mA no-load. Two of these on one 6 A BEC will brown out a receiver at stall — run a separate servo rail or a BEC with real headroom.
FAQ
BLS8135D or BLS8145D?
Same case and spline; the 8145D gives 48 kg·cm instead of 35 and 0.106 s/60° instead of 0.10, at 73 g instead of 77 g, but stall current rises from 4.0 A to 5.2 A. Choose on the supply, not just the torque number.
What frame rate does the PWM build accept?
50–333 Hz per the inspection sheet. The 800–2200 µs window and 1500 µs neutral are unchanged at any frame rate in that range.
Does the RS-485 build speak Modbus?
The inspection sheet lists RS-485 as the command signal and nothing more. Ask for the register map and the supported function codes before you write the controller code — do not assume a Modbus dialect.
How many servos can share the bus?
The limit is the address space and the current budget of the shared supply. Terminate the pair at both ends and keep the power pair separate from the signal pair.
Other interfaces
Downloads
- XQ-RS8145D inspection specification (PDF, 884 KB)
Torque, speed and current at each supply voltage, mechanical data, control specification, mounting dimensions. - 2D dimension drawing (image)
Mounting hole positions, case depth and overall height; the same drawing is inside the datasheet.
