Battery Pack Voltage Calculator
Calculate nominal, full-charge, and cutoff voltage for cells in series. This calculator is intended for early battery pack voltage planning, system input-voltage checks, charger review, and BMS voltage-window estimates.
BAT-007 only covers series-cell voltage. Use the battery energy, runtime, charging, and discharge calculators for other battery relationships, and reserve full series-parallel capacity analysis for the planned pack configuration calculator.
Engineering tool
Battery Pack Voltage Calculator
Calculate battery pack nominal voltage, full-charge voltage, cutoff voltage, and required series cell count.
Typical lithium-ion nominal voltage is 3.6 V or 3.7 V; LiFePO4 is commonly about 3.2 V.
Maximum charged voltage per cell, such as 4.2 V for many lithium-ion cells.
Minimum allowed cell voltage before protection or system cutoff.
Number of cells connected in series. This must be a whole number.
Pack Nominal Voltage
14.8 V
Result console
- Pack nominal voltage
- 14.8V
- Pack full-charge voltage
- 16.8V
- Pack cutoff voltage
- 12V
- Series cell count
- 4cells
- Voltage range
- 12 V ~ 16.8 V
- Formula used
- Vpack_nominal = Vcell_nominal × Ns
Series-voltage scope
This calculator only models series-cell voltage. It does not change capacity for parallel cells and does not estimate battery energy, runtime, charge current, balancing behavior, or BMS limits.
Battery pack voltage changes across state of charge. Use nominal voltage for energy estimates, full-charge voltage for maximum-voltage checks, and cutoff voltage for minimum operating-voltage checks.
Formula reference
Battery Pack Voltage Formulas
Battery pack voltage is the cell voltage multiplied by the number of cells connected in series. Use nominal, full-charge, and cutoff cell voltages for different design checks.
Vpack_nominal = Vcell_nominal × NsVpack_full = Vcell_full × NsVpack_cutoff = Vcell_cutoff × NsNs = Vtarget / Vcell_nominalVariable definitions
- Vcell_nominal
- Nominal voltage of one cell
- Vcell_full
- Full-charge voltage of one cell
- Vcell_cutoff
- Cutoff voltage of one cell
- Ns
- Number of cells connected in series
- Vtarget
- Desired nominal pack voltage
Worked Examples
1S Li-ion Cell
Cell nominal voltage = 3.7 V, Ns = 1
Pack nominal voltage = 3.7 V × 1 = 3.7 V
2S Li-ion Pack
Cell nominal voltage = 3.7 V, Ns = 2
Pack nominal voltage = 3.7 V × 2 = 7.4 V
3S Li-ion Pack
Cell nominal voltage = 3.7 V, Ns = 3
Pack nominal voltage = 3.7 V × 3 = 11.1 V
4S Li-ion Range
Nominal = 3.7 V/cell, full = 4.2 V/cell, cutoff = 3.0 V/cell, Ns = 4
Nominal = 14.8 V; full = 16.8 V; cutoff = 12.0 V
12 V System Estimate
Target = 12 V, cell nominal voltage = 3.7 V
Exact series count = 3.24. A 3S pack is about 11.1 V nominal; 4S is about 14.8 V.
48 V Battery Estimate
Target = 48 V, cell nominal voltage = 3.7 V
Exact series count = 12.97, so 13S gives about 48.1 V nominal.
Engineering Notes
Battery Cell Voltage
A cell has different voltages at full charge, nominal operation, and cutoff. Do not use one voltage value for every design check.
Nominal Voltage
Nominal voltage is useful for naming packs and estimating energy, but it is not the maximum or minimum terminal voltage.
Full Charge Voltage
Full-charge voltage sets the highest expected pack voltage and must be checked against chargers, converters, protection circuits, and load ratings.
Cutoff Voltage
Cutoff voltage sets the lowest allowed operating point before protection disconnects the load or charger logic stops discharge.
Series Connection
Series cells add voltage. The Ah capacity of a single string does not increase just because more cells are placed in series.
Battery Pack Voltage
Pack voltage is dynamic. It depends on chemistry, state of charge, load current, internal resistance, temperature, and aging.
Lithium-ion Voltage
Many lithium-ion cells are treated as 3.6 V or 3.7 V nominal, 4.2 V full, and around 2.5 V to 3.0 V cutoff depending on the cell and system.
LiFePO4 Voltage
LiFePO4 cells are commonly about 3.2 V nominal and about 3.65 V full charge, so their series count differs from 3.7 V lithium-ion packs.
Lead-acid Voltage
Lead-acid systems are often described as 2 V per cell nominal, with pack voltage varying significantly by charge state and load.
Battery Management System
A BMS should monitor cell voltage, balance cells when needed, and enforce overvoltage, undervoltage, overcurrent, and temperature protections.
Common Mistakes
Using 4.2 V as nominal voltage
4.2 V is full-charge voltage for many lithium-ion cells, not the nominal voltage used for naming a pack or estimating nominal energy.
Ignoring cutoff voltage
Loads and converters must still operate above the pack cutoff voltage or the system may shut down earlier than expected.
Assuming series increases capacity
Series connection increases voltage. Parallel connection increases Ah capacity.
Treating pack voltage as constant
Battery voltage changes during discharge. Check maximum, nominal, and minimum operating voltage.
Ignoring BMS cutoff protection
The BMS may disconnect the pack before the load reaches its own minimum voltage threshold.
Mixing chemistry assumptions
Li-ion, LiFePO4, lead-acid, NiMH, and other chemistries use different voltage ranges.
Support reference
FAQ
What is nominal battery voltage?
Nominal battery voltage is the representative voltage used to describe a cell or pack during normal discharge. It is not the maximum or minimum voltage.
Why is a lithium-ion cell called 3.7 V?
A lithium-ion cell is often called 3.6 V or 3.7 V because that is its typical nominal voltage across much of its discharge curve, even though it may charge to about 4.2 V.
Why is full voltage 4.2 V?
Many lithium-ion cells use 4.2 V as the full-charge voltage. Other chemistries use different values, so always check the datasheet and charger requirements.
How do I calculate pack voltage?
Multiply the voltage per cell by the number of cells in series. For example, 4 cells at 3.7 V nominal produce a 14.8 V nominal pack.
Does series connection increase capacity?
No. Series connection increases voltage. Capacity in Ah stays the same for one series string. Parallel connection increases capacity and is handled by a separate pack calculator.
What is cutoff voltage?
Cutoff voltage is the minimum cell or pack voltage allowed before the load or BMS disconnects the battery to prevent over-discharge.
Why does battery voltage change during discharge?
Battery voltage changes because cell chemistry, state of charge, load current, internal resistance, temperature, and aging all affect terminal voltage.
How many cells are needed for a 48 V battery?
Using 3.7 V nominal lithium-ion cells, 48 V divided by 3.7 V is about 12.97, so a 13S pack is commonly used for about 48.1 V nominal.
Planned Related Engineering Guides
Battery Pack Design
Planned guide topic for future battery content expansion.
Series Cells Explained
Planned guide topic for future battery content expansion.
Nominal Voltage vs Full Voltage
Planned guide topic for future battery content expansion.
Lithium-ion Voltage Guide
Planned guide topic for future battery content expansion.
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Open calculatorEngineering Disclaimer
This calculator provides engineering estimates for battery pack voltage. Real battery systems require chemistry-specific datasheet review, charger compatibility checks, cell balancing, BMS protection, wiring and fuse design, thermal validation, safety certification review, and testing under real operating conditions.