UPS Battery Ride-Through Time Calculator

Translate UPS battery specs into realistic ride-through time by combining nameplate energy, the depth-of-discharge policy, conversion efficiency, and any temperature or aging derates.

Total DC energy storage available at nominal conditions before applying depth-of-discharge limits.
Average real power draw of equipment that the UPS must support during an outage.
Percentage of nameplate capacity you are willing to use before recharging to preserve battery life.
Optional. Defaults to 94%. Accounts for inverter and wiring losses between the battery and load.
Optional. Defaults to 0%. Reduces usable capacity to reflect cold rooms or aged strings.

Engineering planning aid; verify against site acceptance tests and OEM documentation before relying on the estimate for compliance or safety decisions.

Examples

  • 250 kWh capacity, 180 kW load, 70% depth-of-discharge, 94% efficiency, 10% derate ⇒ Usable DC energy 157.50 kWh, delivered AC 148.05 kWh, ride-through 0.82 hours (49.4 minutes).
  • 90 kWh capacity, 60 kW load, 80% depth-of-discharge with default efficiency and no derate ⇒ Usable DC energy 72.00 kWh, delivered AC 67.68 kWh, ride-through 1.13 hours (67.7 minutes).

FAQ

How should I pick the depth-of-discharge percentage?

Use the manufacturer-recommended limit for the desired cycle life. Lead-acid strings often stay within 60–80% DoD, while lithium-ion systems may allow 85–90% depending on warranty terms.

Can I include generator warm-up time?

Yes. Compare the calculated autonomy to your generator start sequence and transfer switch timing to confirm the battery covers the full window with margin.

What if load is not constant?

Input the highest credible average load during the outage interval. For variable workloads, model multiple scenarios or use metered peaks to preserve resiliency headroom.

Additional Information

  • Result unit: hours and minutes of autonomy at the stated critical load.
  • Depth of discharge applies before efficiency losses and optional derates.
  • Derate defaults to 0% and trims usable DC energy when conditions reduce capacity.

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