F1 vs F2 Battery Terminals: Which One Does Your UPS Battery Need?
Short answer: F1 and F2 are the two quick-disconnect (Faston) tab sizes on small sealed lead-acid batteries. An F1 tab is 0.187 in (4.75 mm) wide; an F2 tab is 0.250 in (6.35 mm) wide [1][2]. Order the size your UPS cable connectors were made for. Measure the old tab if the label does not say.
This guide is for anyone replacing the 12 V blocks in a UPS, alarm panel or similar standby equipment: how the two terminals differ, how to tell which one you have, whether one can stand in for the other, and which batteries in our catalogue carry each size. It covers single blocks with tab terminals, not bolt-terminal batteries for large UPS cabinets.
F1 and F2 terminals: the dimensions
Both terminals are flat metal blades that a push-on female connector slides over. They differ only in width. Battery supplier Universal Power Group publishes the dimensions in its terminal chart, and they match the two sizes of the FASTON connector system made by TE Connectivity [1][2].
| Property | F1 | F2 | Source |
|---|---|---|---|
| Tab width | 4.75 mm (0.187 in) | 6.35 mm (0.250 in) | [1][2] |
| Tab thickness | 0.80 mm (0.03 in) | 0.80 mm (0.03 in) | [1] |
| Other names you will see | ".187", "Faston 187" | ".250", "Faston 250" | [2][3] |
| Matching female connector | 0.187 in receptacle | 0.250 in receptacle | [2] |
| Typical example on a 12 V UPS block | Duracell DUR12V-7 (7.2 Ah) | Duracell DUR12V-9 (9 Ah), CSB HR1234W | [6][7][5] |
Why UPS batteries often use F2
A UPS draws a lot of current from a small battery for a few minutes. Battery makers design specific "high-rate" models for that job, and the data sheets below show the larger terminal on these models:
- CSB's HR1234W, a 12 V high-rate block "designed for high-rate UPS" service, lists an F2 Faston Tab 250 terminal and a maximum discharge current of 130 A [5].
- Yuasa's NP7-12L, a general-purpose standby block, lists a 6.35 mm Faston terminal and a maximum discharge current of 70 A for one minute and 210 A for one second [4].
- Eaton's RBC51, a cross-brand replacement cartridge which Eaton lists for APC, Belkin, Best, Powerware, Liebert and other UPS brands, is a single 12 V 9 Ah block with F2 terminals [9]. We stock an aftermarket RBC51-compatible replacement battery.
That is a pattern, not a rule: several 7 Ah UPS blocks still ship with F1 tabs, and some makers offer the same battery in both versions. The battery you remove, and the connectors on your UPS cable, decide what you order.
How to tell which terminal you have
- Read the label or model number. Many makers put the terminal in the part number or the specification table: CSB writes "F2" in its HR1234W specifications [5], and our product pages state the terminal for each battery [6][7].
- Measure the tab. A ruler or caliper settles it: about 4.8 mm is F1, about 6.3 mm is F2. Measuring the old battery's tab is the most reliable method [3].
- Look at the cable connector. The female connector on the UPS wiring is sized for one tab. If it slid on firmly and needed a pull to remove, it matched.
- Do not trust the letter alone. Some makers use T1 and T2 for these widths, while in Universal Power Group's chart the T series is a different terminal [1]. Read the width in the data sheet.
Can an F1 battery replace an F2 battery, or the reverse?
Not directly. An F1 receptacle will not fit over an F2 tab, and an F2 receptacle on an F1 tab is loose. A loose push-on connection is a poor contact, and in a UPS that carries high current for minutes at a time, a poor contact heats up exactly when the load depends on it.
Adapters exist: Digi-Key lists clip-on adapters that convert a 0.187 in terminal to 0.250 in, and the reverse [3]. They are a stopgap when the right battery is not available. Each adapter adds two more contact surfaces in the current path, so in a UPS the better fix is the battery with the matching terminal. Never crimp, bend or file a tab to make a connector fit.
| Old battery | Replacement on hand | Advice |
|---|---|---|
| F2 | F2 | Fits as intended. Check voltage, capacity and height too. |
| F1 | F1 | Fits as intended. Check voltage, capacity and height too. |
| F2 | F1 | Connector will be loose. Order the F2 version, or use an F1-to-F2 adapter only as a short-term measure [3]. |
| F1 | F2 | Connector will not go on. Order the F1 version, or use an F2-to-F1 adapter only as a short-term measure [3]. |
| Either | Unknown | Measure both tabs before installing. |
The terminal is only one of five things to match
Two batteries with the same terminal can still be the wrong part. Before you order, match all five:
- Voltage: 12 V for most UPS blocks, 6 V in some older or larger units.
- Capacity: the same Ah rating or the one the UPS maker specifies. A different capacity changes runtime and charging.
- Size, including height: 12 V 7 to 9 Ah blocks share a 151 x 65 mm footprint, but heights differ. Our Nitro N12-9.0T2 is 94 mm tall and the Duracell DUR12V-9 is 102 mm (product-page heights) [8][7]. In a tight battery tray or a pre-wired cartridge, 8 mm matters.
- Terminal: F1 or F2, as above.
- Case rating: some sites require a flame-retardant (UL94 V-0) case; standard cases are often UL94 HB, with V-0 offered as an option [4][5].
If your UPS uses a pre-wired cartridge rather than loose blocks, order the cartridge by its number instead: our RBC and CyberPower cartridge cross-reference and the Tripp Lite cartridge cross-reference list them by UPS model. For an APC Back-UPS 1500, see which battery fits each Back-UPS 1500 generation.
F1 and F2 batteries in our catalogue
These 12 V sealed lead-acid blocks state their terminal on the product page. They are sold in multi-packs; check the pack size on each page.
| Battery | Voltage and capacity | Terminal |
|---|---|---|
| Duracell DUR12V-9 | 12 V, 9 Ah | F2 (0.250 in) |
| Duracell DUR12V-12 | 12 V, 12 Ah | F2 (0.250 in) |
| Duracell DUR12V-18 | 12 V, 18 Ah | F2 (0.250 in) |
| Duracell DUR12V-5-03 | 12 V, 5 Ah | F2 (0.250 in) |
| Duracell DUR12V-7 | 12 V, 7.2 Ah | F1 (0.187 in) |
| Duracell DUR12V-5 | 12 V, 5 Ah | F1 (0.187 in) |
| Duracell DUR12V-4.5 | 12 V, 4.5 Ah | F1 (0.187 in) |
| Nitro N12-9.0T2 | 12 V, 9 Ah | T2 (check the width in the data sheet) |
Browse the full ranges: sealed lead-acid batteries, AGM batteries and all UPS replacement batteries. For the differences between AGM, gel and lithium blocks, read our guide to UPS replacement battery types.
Installing the new battery safely
- Switch the UPS off and disconnect it from the wall before opening the battery compartment, unless the manual describes a hot-swap procedure.
- Photograph the wiring before you remove anything, and reconnect red to positive and black to negative.
- Push each connector fully onto its tab. It should need a firm pull to remove.
- Replace all blocks in a series string at the same time; do not mix old and new.
- Recycle the old battery through a lead-acid battery collection point.
For a server room or a three-phase UPS with many strings, ' UPS battery replacement service handles the swap on site and tests the new battery under load.
Sources
- Universal Power Group, "Terminal Configurations" chart (F series Faston tabs: F1 width 4.75 mm, F2 width 6.35 mm, thickness 0.80 mm). powerwerx.com
- TE Connectivity FASTON .187 tab (4.75 mm) and FASTON .250 tab (6.35 mm), product listings at RS Components. .187 and .250
- Digi-Key, "Battery Terminals and Adapters" (F1 = 0.187 in, F2 = 0.250 in; adapters 522-1019-ND and 522-1020-ND; measure the old tab). forum.digikey.com
- Yuasa, NP7-12L technical data sheet (Faston 6.35 terminal; maximum discharge current 70 A for 1 minute, 210 A for 1 second; ABS UL94 HB, V-0 option). docs.rs-online.com
- CSB Battery, HR1234W data sheet (F2 Faston Tab 250; maximum discharge current 130 A; designed for high-rate UPS). csb-battery.com
- UPSPLUSBATTERY, Duracell DUR12V-7 product specifications (F1 quick disconnect, 0.187 in). upsplusbattery.ca
- UPSPLUSBATTERY, Duracell DUR12V-9 product specifications (F2 quick disconnect, 0.250 in; 151 x 65 x 102 mm). upsplusbattery.ca
- UPSPLUSBATTERY, Nitro N12-9.0T2 product specifications (terminal T2; 151 x 65 x 94 mm). upsplusbattery.ca
- Eaton (Tripp Lite by Eaton), RBC51 replacement battery cartridge (single 12 V 9 Ah block with F2 terminals, cross-brand). tripplite.eaton.com
Written by the UPSPLUSBATTERY technical team. Published 10 October 2026.
