My PC runs normally on mains power, but when the power goes out and my pure-sine inverter switches to battery, it behaves differently depending on the workload. During normal desktop use or light gaming, the PC stays on. During GPU-heavy gaming, the PC shuts down and restarts after about 5–8 seconds. The monitor also turns off, while the inverter itself remains running.
The system uses a Corsair CX550 PSU and draws roughly 316 W while gaming. The inverter is rated at 900 VA and over 700 W, with a 240 Ah battery. It has built-in UPS functionality rather than being paired with a separate UPS. Mains voltage fluctuates but normally stays above the inverter's stated 180 V minimum.
Since the inverter is not obviously overloaded and produces a pure-sine output, could the problem be its transfer time when switching from mains to battery? Or could the PSU, battery condition, voltage sag, or a brief high-load transient be responsible? What should I test first?
2 Answers
Pure sine wave only describes the shape of the battery output; it does not guarantee a fast switchover or stable voltage during the transition. Check the inverter manual for its transfer time and test with another known-good UPS or online UPS. If the PC remains running through that test, the inverter's transfer behavior is the likely culprit. Also test the battery under load and inspect the inverter's low-voltage or overload logs if available.
The most likely cause is the transfer gap. A built-in or offline UPS can take several milliseconds to switch to battery, and the PSU may only tolerate that gap for a limited time. Under GPU load, its input capacitors are being used more heavily, so the same transfer delay can cause a reset even though the average power draw is well below the inverter's advertised wattage.
So would adding a dedicated UPS between the inverter and the PC help?