UPS Battery Bank Calculator
Count series blocks and parallel strings for UPS battery banks—48 V, 110 V, 240 V, and custom string voltages.
Quick answer
Battery bank layout turns a planning Ah target into orderable blocks. Example: 200 Ah at 240 V using 12 V × 100 Ah blocks → 20 blocks in series × 2 parallel strings = 40 blocks total (400 Ah installed). Get Ah from the UPS battery calculator, then verify minutes in the runtime calculator. Hub: UPS calculator.
Quick UPS Battery Bank Calculator
Defaults: 200 Ah @ 240 V, 12 V × 100 Ah blocks, 10% aging margin.
20 × 12 V in series per string · 3 parallel strings · 300 Ah installed.
Advanced Battery Bank Calculator
Quick Examples
Battery Bank Results
Engineering disclaimer
Planning only. C-rate, fuse per string, rack weight, and OEM discharge tables override block counts—verify with vendor tools.
Results
60 blocks (20S × 3P) — default example.
Explain this result (summary)
- Planning Ah: 220.0 Ah at 240 V (includes 10% margin).
- Layout: 20 × 12 V blocks in series × 3 parallel strings.
- Order count: 60 blocks total (100 Ah each) → 300 Ah installed @ 240 V.
Operational guidance
Bank meets planning Ah
Installed 300 Ah covers the planning target—confirm C-rate, rack weight, and fuse layout with the OEM before ordering.
Block Ah vs total blocks
| Block Ah | Total blocks |
|---|---|
| 26 | 180 |
| 38 | 120 |
| 55 | 80 |
| 65 | 80 |
| 100 (your value) | 60 |
| 120 | 40 |
| 200 | 40 |
People also ask
- How many 12 V batteries for a 240 V UPS string? Series count = 240 ÷ 12 = 20 blocks per string. Parallel strings depend on required Ah and each block's Ah rating.
- How is this different from the UPS battery calculator? The battery calculator gives total Ah at a string voltage. This tool splits that into series blocks and parallel strings for ordering.
- Should I enter Ah or kW + minutes? Use Ah if you already sized energy in the battery calculator. Use kW + minutes to derive Ah here in one step.
- What next after block count? Enter parallel strings and Ah in the runtime calculator to verify backup minutes.
Battery bank planning guidance
- Series: Blocks in series raise voltage (12 V × N). Match UPS nominal DC bus.
- Parallel: Strings in parallel add Ah and share discharge current.
- Ah vs layout: Use battery Ah first; use this tool to order blocks.
- Runtime check: Enter strings + Ah in runtime.
Common string voltages (planning)
| Bus V | 12 V blocks / string | Typical use |
|---|---|---|
| 48 V | 4 | Small rack, telecom |
| 110 V | 10 (≈120 V class) | Mid-size UPS |
| 240 V | 20 | Large three-phase UPS |
Battery bank formula
Series blocks = ⌈String V ÷ Cell V⌉ · Parallel strings = ⌈Planning Ah ÷ Block Ah⌉ · Total blocks = Series × Parallel
Frequently Asked Questions
How many 12 V batteries for a 240 V UPS string?
Twenty blocks in series per string. Parallel strings depend on required Ah and each block Ah rating.
How is this different from the UPS battery calculator?
Battery calculator gives total Ah. This tool splits Ah into series blocks and parallel strings for ordering.
Can I size from kW and minutes here?
Yes—switch to energy mode or use the battery calculator first, then enter required Ah here.
What about 2 V cells?
Set cell voltage to 2 V; series count = string voltage ÷ 2. Confirm with OEM string diagrams.
What is the next step?
Verify minutes in the runtime calculator with parallel strings and block Ah filled in.
How it works
Battery bank layout converts planning amp-hours at a UPS DC bus voltage into orderable blocks—series count for string voltage and parallel strings for total Ah using commercial block ratings.
Series blocks multiply cell voltage to match the UPS nominal bus. Parallel strings add amp-hour capacity and share discharge current subject to OEM C-rate limits.
Use the UPS battery calculator for Ah energy sizing first, then this tool for procurement layout, then the runtime calculator to verify minutes with strings entered.
Formula and sources
Series = ceil(String V / Cell V); Parallel = ceil(Planning Ah / Block Ah); Total blocks = Series × Parallel
Planning Ah includes aging margin applied before parallel string count.
Actual string voltage may differ slightly from nominal bus when block count is rounded up.
Worked examples
- 240 V bank with 200 Ah planning target
Twenty 12 V blocks in series per string; two parallel strings of 100 Ah blocks yields 40 blocks and 400 Ah installed.