Sourcing Motorized Curtains From China: Torque Margins, Inrush Current and the App That Dies

Motorised curtains look like a trivially simple product: a tube, a motor, a rail, a remote. Then you install five hundred units in a hotel and discover that the motor somehow can't open a curtain that weighs 4 kg, or that two units on the same track move at different speeds because the factory used two different gearboxes, or that the "quiet" motor produces a whine that guests complain about at 6 a.m.

I've helped source these for both retail kits and project installations, and the failure patterns are consistent enough that I keep a checklist. Here's what actually matters.

The motor is where the cost lives

Almost every motorised curtain uses a single DC gear motor, usually 12 V or 24 V, with a planetary gearbox. The torque rating on the label is peak or stall torque, and stall torque is useless — you need continuous running torque with margin. A rule of thumb buyers use is to take the rated pull force and derate it by 40% for a track with any curve or for a curtain with heavy blackout lining.

Ask for the gear ratio and the motor's no-load current draw. A cheap supplier will use a smaller motor with a higher gear ratio to hit the same torque number, and that combination is slow and noisy. The better motor spins faster and uses a lower ratio, so it's quieter at the same output. This is the single biggest quality differentiator between a budget unit and a mid-tier one, and it's invisible on a spec sheet unless you ask.

Noise is measured in decibels at a stated distance, and only matters if you know the distance. "35 dB" means nothing if they measured at 3 meters in a padded room. Ask for the measurement setup, or better, request a sample with a phone video of the unit running on a real track.

Power and backup

Track current draw at startup, not running. Inrush on a brushed motor can be several times the steady state, and a wall adapter that's fine at running current will brown out and reset the controller. Many "randomly stops halfway" complaints trace back to an undersized adapter, not the motor.

For hotel and project work, buyers increasingly want a battery backup so curtains still close in a power cut. That means LiFePO4 or NiMH packs with a charge controller, and it means the unit can report its battery state. If the supplier's controller can't report battery percentage over the bus, you'll be replacing batteries on a schedule instead of a signal, which is expensive at scale.

Control protocol and the cloud trap

This is where cheap units silently become un-maintainable. A controller that only talks to the supplier's own app is a liability: if the app is abandoned or the server goes down, every unit you sold becomes a dumb tube. Push for at least one open path — a dry contact input, an RS-485 or Modbus interface, or Zigbee or Matter support. For hospitality, dry contact plus a manual pull cord is the minimum that keeps the installation working regardless of what happens to the vendor.

If you do accept a Wi-Fi cloud product, get contractual guarantees on API availability and server lifetime, and keep a local fallback. I've seen an entire product line orphaned when a Shenzhen app team shut down.

The checklist to send before sampling

Maximum curtain weight and track length, including any bends
Continuous torque with a 40% margin, plus gear ratio and motor current draw
Noise in dB with the distance and test method stated
Inrush current and the recommended adapter rating
Control options: dry contact, RS-485/Modbus, Zigbee, Matter, or app-only
Battery backup chemistry and whether state-of-charge is reportable
Certifications: CE, FCC or RED for the radio, and the safety report

Motorised curtains are a product where the difference between a good batch and a bad one is almost entirely in the motor and the control interface, and both are things a trading company can't answer. If your supplier can talk gear ratios and inrush current, you're probably talking to the right people.