Battery Pack Calculator
Design battery packs from individual cells. Calculate pack voltage, capacity, energy, and maximum current for any series-parallel cell configuration.
Cell Parameters
LFP: 3.2V, NMC: 3.7V, NCA: 3.6V, Lead-Acid: 2.0V
Amp-hour capacity of a single cell.
Sets pack voltage. 8 × 3.2V = 25.6V for a 24V nominal system.
Sets pack capacity. 4 × 100Ah = 400Ah pack capacity.
Maximum safe continuous discharge current per cell.
Pack Specifications
Configuration Summary
8S4P — 32 total cells (8 series × 4 parallel)
Mathematical Formulas
A battery pack's electrical characteristics are determined by the number of cells in series and parallel:
Total cells = Series Count × Parallel Count. All cells must be identical in chemistry, capacity, and age.
Worked Engineering Example
Given cell parameters:
- Cell voltage: 3.2V (LFP) | Cell capacity: 100Ah
- Series count: 8 | Parallel count: 4
- Max current per cell: 50A
Step 1: Calculate pack voltage:
Step 2: Calculate pack capacity:
Step 3: Calculate pack energy:
Step 4: Calculate max continuous current:
Result: An 8S4P pack of 32 × 100Ah LFP cells delivers 25.6V, 400Ah, 10.24 kWh, with a 200A continuous discharge limit.
Frequently Asked Questions
What is the difference between series and parallel cell connections?
In series, cells are connected end-to-end to increase voltage (e.g., 8 × 3.2V cells = 25.6V). In parallel, cells are connected side-by-side to increase capacity (e.g., 4 × 100Ah cells = 400Ah). A battery pack typically uses both: series for voltage, parallel for capacity.
How do I choose the right cell for my battery pack?
Select a cell whose nominal voltage matches your target pack voltage when arranged in series. Common choices: LFP (3.2V nominal) for safety and cycle life, NMC (3.7V nominal) for higher energy density. Ensure the cell's maximum continuous discharge current meets your load requirements.
What does the SxP notation mean?
SxP notation describes a battery pack's configuration. 'S' = number of cells in series (sets voltage), 'P' = number of cells in parallel (sets capacity). For example, 8S4P means 8 cells in series and 4 parallel strings, totaling 32 cells.
Can I mix different cell types in a pack?
No. Never mix different cell chemistries, capacities, or age conditions in a single pack. Mismatched cells cause uneven charge distribution, reduced performance, safety hazards, and accelerated degradation. Always use identical cells from the same manufacturer and batch.
How many cells do I need for a 48V battery?
For LFP (3.2V nominal): 16S = 51.2V nominal (common for 48V systems). For NMC (3.7V nominal): 13S = 48.1V or 14S = 51.8V. The exact count depends on your chemistry and the voltage range of your inverter.
What is the total cell count formula?
Total cells = Series count × Parallel count. For example, an 8S4P configuration uses 32 cells. An 16S2P configuration uses 32 cells but produces double the voltage at half the parallel capacity.
How does parallel count affect max current?
Maximum pack current = Cell max current × Parallel count. If each cell supports 50A continuous, a 4P configuration supports 200A total. This is the safe continuous discharge limit for the entire pack.
Should I design series-first or parallel-first?
Series-first (S then P) is standard for most applications — it creates a high-voltage string that is then paralleled for capacity. Parallel-first (P then S) can be safer for high-current applications but requires careful busbar sizing.
What voltage should I target for my application?
12V: Small portable systems. 24V: Medium off-grid, RV. 48V: Residential solar, telecom, most modern inverters. Higher voltage reduces current for the same power, enabling thinner cables and lower losses.
How do I account for BMS overhead?
BMS units consume 10–50mA continuously for monitoring and balancing. Over a month, this can drain 7–36 Ah. Factor BMS standby consumption into very low-load or long-autonomy applications.
Can I add cells to an existing pack?
Only add identical cells (same chemistry, capacity, manufacturer, batch) to an existing pack. Adding different cells creates imbalance. New cells should be pre-balanced to match the existing pack voltage before connection.
What Is Battery Pack?
Why This Calculation Matters
→ Incorrect series count produces the wrong voltage — too few cells means the inverter won't operate; too many risks overvoltage damage.
→ Insufficient parallel count means the pack cannot deliver the required continuous current, causing BMS shutdowns under load.
→ Mixing cells from different batches or manufacturers causes imbalance, accelerated degradation, and potential safety hazards.
→ Undersized packs lead to deep discharge cycles that reduce battery lifespan, while oversized packs waste capital.
→ Understanding pack configuration is essential for BMS selection, as BMS units are rated for specific series counts and chemistry.
Practical Applications
EV Battery Modules
Design battery modules for electric vehicles with specific voltage and capacity requirements.
DIY Powerwall Builds
Configure lithium battery packs for home energy storage from individual prismatic or cylindrical cells.
Marine Propulsion Banks
Design high-capacity, high-current battery banks for electric boat propulsion systems.
Portable Power Stations
Size compact battery packs for camping, emergency, and mobile power applications.
Telecom Backup Systems
Configure 48V battery banks from individual cells for telecom tower backup power.
Robotics & UAV
Design lightweight, high-discharge battery packs for robotic and drone applications.
Why Trust These Calculations?
Pack configuration formulas (V_pack = V_cell × S, Ah_pack = Ah_cell × P, Wh = V × Ah) are fundamental electrical engineering relationships. All calculations are transparent and follow standard industry conventions for battery pack design.
View our full methodology →Parallel String Calculator
Design series/parallel configurations for target voltage and capacity.
C-Rate Calculator
Calculate charge and discharge rates for your cells.
Battery Sizing Calculator
Determine overall bank size for your application.
Runtime Calculator
Compute runtime from load wattage profiles.
Degradation Estimator
Estimate capacity fading over time.
SOC Estimator
Interpolate State of Charge from voltage.
References & Further Reading
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