APC Back-UPS 500 Uninterruptible Power Supply Good working condition The APC Back-UPS CS 500 (BK500EI) is a compact UPS (Uninterruptible Power Supply) designed for PCs, routers, small servers, network equipment, and office electronics. Main features Power capacity: 500 VA / 300 W UPS topology: Standby / Off-line UPS Input / Output voltage: 230 V AC Waveform: Stepped approximation to sine wave Transfer time: ~6 ms typical, 10 ms maximum Battery type: Sealed lead-acid (VRLA) rechargeable battery User-replaceable battery: Yes Outlets: Typically 4 IEC C13 battery-backed outlets (some variants have 6 outlets) USB communication port: Yes, for automatic PC shutdown and monitoring Surge protection: Protects against spikes, surges, and blackouts Runtime: ~14 min at 50% load ~3–4 min at full 300W load Physical specifications Dimensions: approx. 91 × 165 × 284 mm Weight: around 6.0–6.3 kg Form factor: Tower/Desktop Typical use cases Desktop PCs Routers and switches NAS systems Small medical or laboratory electronics POS systems Home office backup power