Silent UPS for Gaming PC (1 kW) — 24V LiFePO₄ + Pure-Sine Inverter/Charger

Line-interactive, low-noise backup with fast transfer. No cheap batteries, no screen flickers.

What You’re Building

Output: 120V AC 1,000W continuous UPS transfer ≈ 10–20ms 24V LiFePO₄ ≈ 2.56 kWh pack

Designed for PCs, monitors, DAC/amps, routers, capture rigs. Clean sine, fast switchover, hours of runtime.

Safety First

No backfeeding. Never tie inverter output into house wiring without a transfer switch.
Fuse near battery. Class-T/ANL sized for current (e.g., 125A), placed as close as practicable to + battery.
Gauge up. Expect 40–60A DC at 1kW; use 4 AWG copper for short runs (2 AWG for longer/overkill).

Core Parts

24V→120V pure-sine inverter/charger (1,000W) with UPS/fast-transfer mode
24V 100Ah LiFePO₄ (or 2× 12V 100Ah in series), BMS built-in
125A Class-T fuse + holder; 100–125A DC breaker
Shunt-type battery monitor (≥200A)
4 AWG copper battery leads, ring lugs, heat-shrink
AC inlet (charge), quality outlet/strip on inverter AC OUT

Layout Snapshot

[Wall AC] -> [Inverter/Charger AC IN]
                 |
24V LiFePO₄ -> [125A Class-T] -> [100–125A DC Breaker] -> [Inverter DC]
                 |
             [AC OUT] -> [UPS Strip] -> PC • Monitor • Router

UPS mode = fast transfer; PC stays alive during grid blips.

Build Steps

Plan & mount: Short DC runs, clean airflow. Mark pass-throughs and strain reliefs.
Battery & protection: Strap battery; install Class-T (≈125A) within 8–10″ of +; then DC breaker to inverter.
Crimp & land: 4 AWG copper, proper crimper, heat-shrink, label. Torque lugs to spec.
AC wiring: AC IN from wall; AC OUT to a dedicated strip for the PC gear.
Program charger: LiFePO₄ profile — absorb ≈ 28.4–28.8V; float ≈ 27.0–27.6V (or disabled per battery maker).
Checks: Breaker OFF → continuity OK → polarity OK → power ON → idle normal.
Transfer test: With PC running, pull wall AC; screens should stay up. Reconnect; charger resumes.

Runtime Quick Math

Usable ≈ 2.56 kWh × 0.9 DoD × 0.9 eff ≈ ~2.1–2.3 kWh.

300 W stream rig → ~7–7.6 h
600 W gaming → ~3.4–3.8 h
1,000 W max → ~2.0–2.3 h

Pro Tips

Enable UPS/Fast Transfer mode; test once with your PSU.
Keep spiky appliances (heaters, kettles) off this UPS strip.
Label AC IN vs AC OUT so nobody cross-plugs.

Parts Bill (1kW / 24V)

Component	Spec	Amps / Fuse	Notes
Inverter/Charger	24V→120V, 1,000W, UPS mode	AC ≈ 8.3A @ 120V	Transfer ≤ 20ms (model-dependent)
Battery	24V 100Ah LiFePO₄	Charge ≤ 0.5C (~50A)	Set absorb/float per maker
Main Fuse	Class-T	≈ 125A	Within 8–10″ of + battery
DC Breaker	Service disconnect	100–125A	Between fuse and inverter +
Cables	4 AWG Cu (short runs)	~40–60A DC	2 AWG if long/overbuild
Monitor	Shunt (≥200A)	—	All negatives after shunt

Verify ratings in your manuals; local code rules apply.