What is the backup time for a 48 volt 100 Ah battery?
The backup time of a 48V 100Ah battery depends on the load power and system efficiency. A general formula is: Backup Time (hours) = (Battery Capacity × Voltage × Efficiency) ÷ Load Power. Assuming 80% efficiency and a 1,000W load, it provides ~3.8 hours. For lower loads like 500W, runtime doubles to ~7.7 hours. Always factor in inverter losses and depth of discharge (DoD) limitations.
What Is a 48V Server Rack Battery and Its Benefits
How is battery backup time calculated?
Backup time derives from energy capacity divided by load demand, adjusted for inverter efficiency (typically 85–90%). For lithium batteries, 80% DoD is standard. Formula: (48V × 100Ah × 0.8 DoD × 0.85 efficiency) ÷ Load (W) = Hours.
Practically speaking, a 48V 100Ah lithium battery stores 4.8kWh gross energy. Accounting for 80% DoD and 85% inverter efficiency yields 3.26kWh usable energy. A 500W load would drain this in 6.5 hours (3,260Wh ÷ 500W). Pro Tip: Add 15% buffer to calculations—real-world factors like temperature and aging reduce actual runtime. For example, powering a 1,200W server rack: (4,800Wh × 0.8 × 0.85) ÷ 1,200W ≈ 2.7 hours.
| Load Power | Runtime (Hours) |
|---|---|
| 500W | 6.5 |
| 1,000W | 3.3 |
| 2,000W | 1.6 |
What factors reduce backup time?
Key limitations include inverter inefficiency, temperature extremes, and battery aging. Lithium batteries lose 2-3% capacity annually; lead-acid degrades 5-8% yearly. At -10°C, capacity drops 20–30%.
Beyond basic calculations, voltage sag under high loads forces premature shutdowns. A 48V system may cut off at 42V, leaving unused energy. Pro Tip: Use lithium LiFePO4 batteries—they maintain 95% capacity for 2,000 cycles vs. lead-acid’s 500 cycles. For example, a 48V 100Ah LiFePO4 battery powering a 700W HVAC system lasts ≈4 hours initially but only 3.2 hours after 5 years due to degradation.
Battery Expert Insight
FAQs
Yes, parallel connections increase capacity (e.g., two batteries = 200Ah), doubling runtime at the same load. Ensure identical batteries and use a current-balancing busbar.
How does altitude affect backup time?
Above 3,000m, lithium batteries lose 15% capacity due to reduced air density cooling. Compensate by oversizing battery banks by 20% for high-altitude deployments.