UPS battery capacity is rated inAh (ampere-hours), indicating how much current it can deliver hourly. The core of battery sizing is to match the right battery bank to your load, to get accurate backup runtime — also called battery autonomy.

Professional battery sizing doesn’t only calculate load power. It also takes full account of:

• Ambient temperature

• UPS inverter and system efficiency

• On-site power failure history

• Critical load capacity

• Standby generator availability

• Time needed for load shedding and orderly equipment shutdown

• Installation space, temperature, humidity

• Budget and space trade-off for long runtime

A UPS battery bank can beone single string or multiple parallel strings. A string is made of battery blocks connected in series; the Ah rating of the blocks determines the total battery capacity.

Battery makers provide discharge curves for reference, while professional UPS manufacturers use custom sizing programs tailored to their own UPS performance for more precise matching.

The required battery runtime must be long enough to:

✅ Keep critical loads running during outages

✅ Allow standby generators to start automatically or manually

✅ Complete safe load shedding and system shutdown

One key tip:

Comparing runtime across different UPS brands can be misleading. Always check runtime underthe same load wattage and power factor.

Example for reference:

A 10kVA UPS with 12Ah batteries

▶ 8kW load / 0.8pf ≈ 14 minutes runtime

▶ 6kW load / 0.6pf ≈ nearly 20 minutes runtime

Wrong battery sizing leads to insufficient backup time, wasted cost or shortened battery life.

Need help sizing your UPS battery system?

Contact our team for professional support.

We also provide an online UPS Configurator to match the perfect solution for your loa

Email: hli@daopulse.com