Battery Series Parallel Calculator
Calculate total battery-bank voltage, amp-hour capacity and energy.
Interactive Electrical Calculator
Battery Series Parallel Calculator
Calculate total battery-bank voltage, amp-hour capacity and energy.
Result
Enter values and calculate.
About the Battery Series Parallel Calculator
The Battery Series Parallel Calculator is a free, browser-based tool for battery capacity, runtime, charging time and series/parallel bank sizing. Calculate total battery-bank voltage, amp-hour capacity and energy. Charging time depends on charger current, battery capacity and charge efficiency together, not on any one of those numbers alone.
It's aimed at solar and off-grid system builders, RV and marine owners, backup-power installers, and hobbyists working with lithium or lead-acid packs, who need a fast, reliable number without redoing the math by hand each time.
How the calculation works
The calculator is built around this relationship:
Bank V = battery V × series; Bank Ah = battery Ah × parallel.
Where each input maps to a field in the calculator above:
- One Battery Voltage in V.
- One Battery Capacity in Ah.
- Batteries in Series.
- Parallel Strings.
You can adjust any of these values as many times as you like; the result updates on every change with nothing sent off your device.
A worked example
For example, start with 12 V for one battery voltage, 100 Ah for one battery capacity, 4 for batteries in series and 2 for parallel strings. Those defaults are only a starting point — replace them with your own measured or nameplate values, then press Calculate to get a result specific to your situation.
When to use the Battery Series Parallel Calculator
Typical reasons people reach for the Battery Series Parallel Calculator:
- Sizing a battery bank for a specific backup runtime target.
- Working out how long a charger will take to top up a given battery.
- Converting a battery spec sheet between Ah, Wh and mAh so it can be compared with another product.
- Planning a series/parallel wiring configuration to hit a target system voltage and capacity.
Good practice: Real-world runtime is usually shorter than a simple capacity ÷ load calculation because of inverter losses, temperature and battery age.
Also worth knowing: Depth of discharge matters: a lead-acid battery rated for 100 Ah cannot safely deliver anywhere near 100 Ah of usable capacity, unlike most lithium chemistries.
Frequently asked questions
What does the Battery Series Parallel Calculator calculate?
Calculate total battery-bank voltage, amp-hour capacity and energy.
Is the result exact enough to build from?
The formula above is applied exactly to the values you enter, so the math itself is precise. Real-world results can still differ due to component tolerances, temperature, installation method, equipment efficiency and local code requirements, so treat the output as a strong planning estimate and verify final designs against manufacturer data and the electrical code that applies to your installation.
Does this calculator store or send my data anywhere?
No. The Battery Series Parallel Calculator runs entirely in your browser, and nothing you type is transmitted or stored anywhere.
Why not just estimate this instead of calculating it?
Battery capacity is usually rated in Ah or Wh, while the load is usually rated in watts or amps, so converting between them correctly is the difference between a battery bank that lasts and one that runs flat early.
Can I use this on a phone, or does it need a desktop?
The Battery Series Parallel Calculator works on any modern browser, phone or desktop, and recalculates as soon as you press Calculate. If a result looks off, double-check that every field is filled in with the unit shown next to it (mixing up units, such as W with kW, is the most common cause of an unexpected answer) and re-enter the values.