| 85KG·CM STALL | 0.110S/60° NO-LOAD | 16.8V RATED |
| 92G WEIGHT | StainlessGEARTRAIN | 360°TRAVELCustomizable |
Overview
The BLS8185HV is the same 85 kg·cm servo as the BLS8185D with a high-voltage winding: identical 20 × 40 × 44 mm case, 92 g, same 25T-φ7.96 mm output, same 7075 horn. The difference is where the torque lives — 85 kg·cm arrives at 16.8 V here, not at 8.4 V.
That shift is the whole point of the HV build. On a 4S pack the servo holds its rated torque as the pack sags, where the low-voltage build would already be at its ceiling at 8.4 V. On 2S, the HV build is the weaker of the two: only 42 kg·cm at 8.4 V.
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 |
|---|---|---|---|---|
| 8.4 V | 0.170 s/60° (353 °/s) | 42 kg·cm (4.12 N·m / 583 oz·in) | 320 mA | 4.0 A |
| 12.0 V | 0.140 s/60° (429 °/s) | 60 kg·cm (5.89 N·m / 833 oz·in) | 370 mA | 5.0 A |
| 16.8 V | 0.110 s/60° (545 °/s) | 85 kg·cm (8.34 N·m / 1180 oz·in) | 440 mA | 6.0 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 | 20 × 40 × 44 mm | Case material | Aluminium, CNC |
| Weight | 92 g | Geartrain | Stainless steel |
| Bearings | 2 × ball bearing | Motor | Brushless |
| Output spline | 25T-φ7.96 mm | Horn | 7075 aluminium, CNC |
| 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-RS8185HV servo
- 1 × 7075 aluminium horn
- 1 × mounting screw pack
How to size it
Torque is 42 kg·cm at 8.4 V, 60 at 12.0 V and 85 at 16.8 V, at 0.17, 0.14 and 0.11 s/60°. Below 8.4 V it is not rated. If your machine is 2S, the low-voltage BLS8185D gives you 85 kg·cm instead of 42 for the same money and the same footprint.
Stall current is 6.0 A at 16.8 V. On 4S, check the BEC and the wiring for the 4S voltage, not the 2S one — the current is the same but the pack voltage is doubled, so the same gauge dissipates four times the power in a fault.
FAQ
BLS8185HV or BLS8185D?
Pick by pack. 4S → HV, which reaches 85 kg·cm at 16.8 V. 2S → the low-voltage D, which reaches the same 85 kg·cm at 8.4 V. Running the HV on 2S leaves you with a 42 kg·cm servo.
Can I run it on 3S?
Yes — at 12.0 V it is 60 kg·cm at 0.14 s/60°. That is the middle of its range, not a compromise.
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-RS8185HV inspection specification (PDF, 429 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.
