Which UPS gives 4 hours backup?
To achieve 4 hours of UPS backup time, select a high-capacity online UPS system with scalable external battery banks. For example, a 10kVA UPS paired with 48V 400Ah lithium-ion batteries (split into 4×100Ah parallel strings) typically sustains 4 hours for 2kW loads. Prioritize UPS models supporting modular battery expansion and LiFePO4 chemistry for stable deep-cycle performance. Pro Tip: Always derate UPS capacity by 30% when planning extended runtime to prevent overload tripping.
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What factors determine 4-hour UPS runtime?
Runtime depends on battery capacity, load wattage, and inverter efficiency. For 4-hour backup: Battery Ah = (Load Watts × 4) / (Battery Voltage × 0.85 efficiency). A 3kW load requires ≈700Ah at 48V. Always include 15% capacity buffer for aging.
Practically speaking, achieving 4-hour runtime demands meticulous system design. Start by calculating total connected load—if your servers draw 2.5kW, you’ll need batteries delivering 10kWh (2.5kW × 4h). Lead-acid batteries require double the calculated capacity due to 50% depth-of-discharge limits, while lithium-ion permits 80-90% discharge. For example, a 48V lithium system needs 10kWh / (48V × 0.9) ≈ 232Ah. Transitional tip: Use battery rack systems like EG4 for modular scaling.
Which UPS types support 4-hour backup?
Double-conversion online UPS systems with external battery ports are mandatory. Models like Eaton 9PX or APC Smart-UPS XL support up to 8 external battery packs. Avoid line-interactive designs—their chargers lack high-current capacity for quick recharge.
Beyond basic topology, verify the UPS’s charging specs. A 10kVA UPS needing 4-hour runtime requires at least 40A charging current to replenish 40kWh batteries overnight. Real-world example: The Vertiv Liebert GXT5-9000RT supports 192V battery banks with 100A charging, enabling 4+ hours for 6kW loads. Pro Tip: Confirm battery communication protocols match—some UPS only recognize proprietary battery packs.
| UPS Type | Max External Batteries | 4h Runtime Feasible? |
|---|---|---|
| Desktop UPS | 0 | ❌ |
| Rackmount Online | 4-8 packs | ✅ |
| Tower Line Interactive | 2 packs | ❌ |
How to calculate exact battery requirements?
Use the energy method formula: Battery Ah = (Load W × Runtime h) / (Vbat × ηinv × ηdis). For 4h at 3kW: 3000×4/(48×0.9×0.95)= ≈311Ah. Always round up to next commercial size.
But what if your load varies? Phase balancing becomes critical in three-phase systems. For a 15kVA 480V UPS, divide load equally across phases (5kVA each). Each phase needs 5kVA×0.8pf=4kW → 4kW×4h/(192V×0.85)= ≈104Ah per battery string. Transitional note: Lithium batteries maintain voltage better than lead-acid during discharge, often providing 10-15% extra effective capacity.
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FAQs
Only if it supports external batteries and has sufficient charger capacity. Most UPS under 5kVA lack scalable charging circuits needed for large battery banks.
What’s the cost difference between lead-acid and lithium for 4h backup?
Lithium systems cost 2-3× upfront but last 3× longer. A 10kWh lead-acid setup ≈$3,000 vs lithium ≈$7,000, but lithium saves $4k+ in replacements over 10 years.