UPS Battery Backup

UPS Battery Backup: What to Buy and How to Size It

A UPS bridges dips, surges, and outages so sensitive electronics keep running long enough to work through short events or shut down cleanly. Use the guide below to match topology, capacity, and runtime to your setup.

What a UPS Does

• Voltage regulation: Smooths sags and trims over-voltage (line-interactive/online).
• Surge and noise filtering: Protects against spikes and line noise.
• Instant battery backup: Keeps equipment powered during outages.
• Graceful shutdown: Via USB or network signaling to prevent data loss.

Choose a Topology

Pure Sine Wave & Active-PFC Compatibility

Modern desktops and some AV gear use active PFC and expect a clean waveform. Choose pure sine wave output to avoid buzz, misbehavior under load, or nuisance shutdowns—especially for performance PCs, studio gear, and sensitive instruments.

How to Size Capacity and Runtime

1. List loads and watts: Example: PC 350 W + monitor 40 W + router 15 W + NAS 30 W = 435 W.
2. Add headroom: Multiply by 1.2–1.3 for spikes and growth. 435 W × 1.25 ≈ 544 W.
3. Pick a UPS whose watt rating ≥ your result: A 1000 VA unit may provide 600–900 W; check the watt rating.
4. Choose runtime: 5–10 minutes is enough for safe shutdown; 20–60 minutes rides through short outages. Verify the vendor runtime chart at your specific load.

Tip: Dropping nonessential loads (e.g., the desktop) can turn 10 minutes of runtime for a full setup into 1–3 hours for networking alone.

Typical Runtime Targets

Battery Chemistry: Pros and Cons

• VRLA (sealed lead-acid/AGM): Low cost, widely available, often hot-swappable; typical life 3–5 years (shorter in heat); heavier and larger.
• Lithium-ion: 2–3× cycle life, lighter, smaller; higher upfront cost but lower long-term maintenance for 24/7 use.

Must-Have Features

• Automatic Voltage Regulation (AVR) to reduce battery wear in brownouts.
• Outlet groups: Battery + surge vs surge-only to prioritize essentials.
• Monitoring: USB HID for desktops; optional SNMP/network card for remote alerts and multi-device shutdown.
• Hot-swappable batteries to minimize downtime.
• Data-line protection: Coax/Ethernet surge pass-through to prevent backdoor surges.
• Clear indicators: LCD, load %, runtime estimate, and switchable alarms.

Form Factor & Connectors

• Tower vs rackmount: Tower fits desks/living spaces; rackmount (1U/2U) fits AV/server racks.
• Outlet types: NEMA 5-15R (most US), IEC C13/C19 on pro units—count plugs and brick sizes.
• Depth and airflow: Allow cable clearance and ventilation, especially in racks.

Quick Picks by Scenario

• Home office/study: 600–1000 VA line-interactive; pure sine for active-PFC desktops.
• Gaming setup: 1000–1500 VA pure sine; low transfer time; USB monitoring.
• Networking closet: 600–1000 VA with long runtime; include coax/Ethernet protection.
• Small server/NAS/NVR: 1500–3000 VA pure sine; USB or SNMP for auto-shutdown.
• Studios/AV: Pure sine; line-interactive or online for stable voltage and minimal noise.

Setup & Safety Tips

1. Plug the UPS directly into a grounded wall outlet. Do not place a surge strip between the wall and UPS. If needed, use a power strip on the output side only for low-draw devices.
2. Prioritize loads: Put essentials (PC, router, NAS) on battery outlets; printers, speakers, lamps on surge-only.
3. Avoid high-draw appliances: Do not power space heaters, kettles, or laser printers from battery outlets.
4. Thermal care: Keep vents clear; avoid closed cabinets without airflow. Heat shortens battery life.
5. Test regularly: Quarterly, simulate an outage to confirm runtime and auto-shutdown behavior.
6. Generator use: Prefer line-interactive or online units with pure sine output; let the generator stabilize before connecting loads.
7. Use cases with risk: Do not rely on a consumer UPS for life-support or where failure risks injury; use certified medical/industrial equipment only.

Maintenance

• Environment: 68–77°F (20–25°C) is ideal; every 18°F (10°C) rise can halve VRLA life.
• Dust control: Clean vents periodically.
• Battery replacement: Plan for VRLA every 3–5 years; lithium typically 6–10 years. Use specified cartridges.
• Firmware & calibration: Update firmware; perform vendor-recommended runtime calibration if applicable.

Alternatives and Complements

• Surge protector: Cheap surge defense only—no runtime.
• Whole-home surge suppression: Adds upstream protection; still pair with a UPS for runtime.
• Generator: Long-duration power; use with a UPS to smooth start/stop and fluctuations.

Buyer Checklist

1. Topology: standby (basic), line-interactive (most setups), online (critical).
2. Pure sine wave for active-PFC desktops and sensitive gear.
3. Watts with 20–30% headroom; verify VA to watt rating.
4. Runtime target at your load; consult runtime charts.
5. Outlet count/types and space for power bricks.
6. Monitoring: USB for one device; SNMP for fleets.
7. Battery plan: hot-swappable? Replacement cost/availability?
8. Form factor and ventilation space.

FAQ

How long will my UPS run?
It depends on your load and battery size. Expect ~5–15 minutes at 40–60% load on many desktop-class units; hours for small networking loads. Check the manufacturer’s runtime chart for your exact wattage.

Do I need pure sine wave?
Yes for active-PFC desktops, studio gear, some medical/lab devices, and anything sensitive to waveform quality. It prevents shutdowns and noise issues.

Can I plug a power strip into a UPS?
Yes, on the output side for low-draw devices. Do not put a surge strip or conditioner between the UPS and the wall.

Will a UPS run a laser printer?
Avoid it. Laser printers draw large inrush currents that can trip the UPS. Use a wall outlet or surge-only outlet.

When should I replace the battery?
Replace VRLA batteries about every 3–5 years (sooner if hot or heavily cycled). Replace lithium batteries per the vendor’s life rating or when runtime warnings appear.