High-rate UPS batteries

When a UPS has to carry a heavy load for only a few minutes, the Ah rating stops being the useful figure. High-rate batteries are VRLA AGM blocks with plates and internal links built for very fast discharge, and they are chosen by the watts per cell they deliver over 5, 10 or 15 minutes.

This section carries 12 V blocks from the RITAR HR series.

Why watts matter more than amp-hours here

A battery's Ah figure comes from a slow discharge, typically over 20 hours. In a UPS of any size the discharge lasts minutes, and at that rate a conventional block delivers far fewer Ah than its label suggests. High-rate datasheets therefore include constant-power tables (W/cell) for several durations and end voltages. Some series even put that number in the model name.

Quick sizing method

• Start from the real load in watts and divide it by inverter efficiency (around 0.9).
• Divide that figure by the total number of cells in the string: every 12 V block has 6.
• Look up the manufacturer's table for the model that delivers those W/cell for the runtime you need.

Rough example: a 3,600 W load at 0.9 efficiency asks 4,000 W of the batteries; with four 12 V blocks (24 cells) that is about 167 W per cell. Add headroom for ageing and temperature.

Installation and care

These blocks nearly always sit in long series strings, so every unit should share model and batch, with links torqued to spec and no temperature gap between shelves. A loose link under fast discharge creates heat and voltage drop that the UPS reads as a flat battery.

Browse the RITAR range, compare with standard UPS batteries or go back to stationary batteries.

High-rate battery FAQ

Can a standard AGM block of the same size replace a high-rate one?

It will fit and connect, but real runtime will be shorter and the UPS may cut out early under heavy load. Always compare the W/cell tables.

Are they suitable for daily cycling?

Not really. They are designed for float service with short, infrequent discharges; daily cycling calls for a different technology.

Which end voltage should I use in the calculation?

Whatever the UPS is set to, usually between 1.60 and 1.75 V per cell. A lower cut-off extracts more energy but stresses the battery more.