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ITGlossary · UPS technology
Cold Start Function
A feature that allows a UPS to be started directly from the battery without utility power.
Technical level:Intermediate
Normally a UPS needs mains voltage to switch on. With the cold start function you can turn it on while power is out, drawing energy from the battery alone. Usually it is enough to hold the power button for a few seconds, but the exact procedure varies by model.
The function is useful when an outage is already under way and a device must run: for example, to save your work, open an electric door, communicate through a router or properly shut down a server that had gone off.
Remember that runtime in cold start is whatever remains in the battery, which may already be partly drained. Connect only the absolutely essential loads, and check in advance that your model supports the function.
Related terms
- Auto RestartA UPS feature that automatically restarts the system after utility power returns following a shutdown.
- BypassA path that feeds the load directly from the mains, without protection, when the UPS is overloaded, faulty or under maintenance.
- InverterThe component inside a UPS that converts DC power from batteries back to usable AC power.
- Redundant Power SupplyA second power supply inside a server or switch that takes over without interruption if the first one fails or loses its feed.
- Transfer TimeThe brief power gap when a UPS switches from mains to battery, typically 2–10 ms for line-interactive models and zero for online ones.
- AutonomyThe time a battery-powered system (like a UPS) can continue operating critical loads after a power failure.