What a UPS does for a powered door

An uninterruptible supply for a shutter is not the same product as one for a computer. The load is a motor, and motors fail differently.

A UPS — uninterruptible power supply — holds a load up when the mains goes. Hospitals, data centres and control systems use them; so does a powered door, for a simpler reason. A shutter without power is a shutter that cannot be opened.

The load is what makes a door UPS a different product. A computer draws a steady few hundred watts; a shutter motor draws a large current for a second or two at the start of every cycle and almost nothing in between. A unit sized on average draw will trip on the start.

So the specification is by motor capacity, not by wattage: a unit rated for motors to 400 kg, or to 800 kg, with standby measured in tens of hours rather than minutes. A door may need to cycle two or three times across a two-day outage, which is a very different duty from holding a server up for fifteen minutes.

Battery chemistry is the other decision. Lithium iron phosphate is rated for around 2,000 charge cycles against roughly 500 for lead-acid, and holds above 80% of rated capacity at the end of them.