Server City UPS runtime and size
How long will the UPS hold?
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Result
| Estimated runtime | about 13-22 minutes Allows for fast discharge (lead-acid battery, Peukert 1.1-1.25). The maker's runtime chart for your model is the better guide. |
|---|---|
| Straight-line upper bound | 31 minutes (no allowance for high load, cold or battery age) |
| Stored energy used | 216 Wh x 90% x 80% |
| UPS size for this load | at least 417 VA (300 W / 0.9 + 25% headroom) and at least 375 W (300 W + 25%). Check both the VA and the W on the UPS label: many consumer units are rated about 0.6 W per VA, so a 1500 VA unit may carry only 900-1000 W. |
Straight line = volts x amp-hours x efficiency x usable share / watts. Battery amp-hours are rated over 20 hours; drawn faster, a lead-acid battery gives less, so the range applies Peukert's law with an exponent of 1.1 to 1.25. Runtime is shorter still in the cold and as batteries age. A typical small UPS has a 12 V or 24 V bank of 7-9 Ah batteries: check the label on the battery.