| 25KG·CM STALL | 0.070S/60° NO-LOAD | 8.4V RATED |
| 65G WEIGHT | StainlessGEARTRAIN | 360°TRAVELCustomizable |
Overview
The BLS325 is a low-profile brushless servo: 41 × 20.5 × 28.5 mm, 65 g, 25 kg·cm at 8.4 V. The 20.5 mm thickness is the point of the design — it fits where a standard 20 mm-tall case plus horn will not clear a canopy or a frame rail.
A brushless motor drives a stainless steel geartrain on two ball bearings, with a 25T-φ5.96 mm spline and a POM horn. There is no mechanical stop on the output, and the case is a CNC aluminium block with fins cut into the sides rather than a plastic shell with a heatsink sticker.
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 | 0.120 s/60° (500 °/s) | 17.5 kg·cm (1.72 N·m / 243 oz·in) | 190 mA | 3.5 A |
| 7.4 V | 0.090 s/60° (667 °/s) | 22 kg·cm (2.16 N·m / 306 oz·in) | 220 mA | 4 A |
| 8.4 V | 0.070 s/60° (857 °/s) | 25 kg·cm (2.45 N·m / 347 oz·in) | 250 mA | 5 A |
Control specification
| Item | Specification |
|---|---|
| Command signal | RS-485 |
| Amplifier | Digital controller |
| Dead band | 2 µs |
| Rotating direction | CCW (1000–2000 µs) |
| Travel | 360°, customizable |
Mechanical specification
| Item | Specification | Item | Specification |
|---|---|---|---|
| Dimensions | 41 × 20.5 × 28.5 mm | Case material | Aluminium, CNC |
| Weight | 65 g | Geartrain | Stainless steel |
| Bearings | 2 × ball bearing | Motor | Brushless |
| Output spline | 25T-φ5.96 mm | Horn | Plastic, POM |
| Lead / connector | 300 mm, 3-wire | Mechanical limit | No limit |
| 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-RS325 servo
- 1 × POM horn set
- 1 × mounting screw pack
Optional: metal horn, sold separately.
How to size it
Torque tracks the rail: 17.5 kg·cm at 6.0 V, 22 at 7.4 V and 25 at 8.4 V. A 2S LiPo sits near 7.4 V for most of its discharge, so plan around 22 kg·cm and treat 25 as the fresh-pack number.
Stall current is 5 A at 8.4 V against 250 mA no-load. A shared BEC that also feeds four of these needs 20 A of headroom on stall — check the BEC before blaming the servo for brownouts.
FAQ
What makes it low-profile?
The case is 20.5 mm thick instead of the usual 28–30 mm, so the servo sits flatter on the mounting surface. That is what lets it fit under a canopy or inside a narrow fuselage.
Does it fit a standard 25T horn?
Yes — 25T spline, φ5.96 mm centre. A POM horn set ships in the box; aluminium horns are a separate item.
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-RS325 inspection specification (PDF, 751 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.
