Cell Layout Calculator

Work out how the cells in a tool pack are arranged in series and parallel, and what that gives you.

Cells joined in series (S) add their voltage. Groups of cells joined in parallel (P) add their capacity. A pack described as 5S2P has 5 groups in series, each with 2 cells in parallel: 10 cells. Everything is worked out in your browser. Nothing is saved or sent anywhere.

1. The pack

Pick the pack voltage, then either the number of parallel groups or the capacity you're aiming for.

2. The cells

Use the datasheet figures for the exact cell model. Tool packs normally use lithium-ion cells (3.6V nominal).

Full charge is 4.2V per cell.
18650 cells are often 1,500–3,500 mAh; 21700 cells 3,000–5,000 mAh.

3. Results


  
How it was worked out

  
    

    


    

    What this does and doesn't tell you
    

      
  
    • The layout is worked out from nominal voltages. Real packs from one brand can differ, so check the actual pack before ordering cells.
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    • The current figure is the cells' combined continuous rating. The pack's protection board, nickel strip and terminals may limit it to less.
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    • Every cell in a pack must be the same model, the same capacity and from the same batch. Never mix old and new cells.
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    • Lithium-ion tool packs can short, overheat and catch fire if they're damaged, wired wrongly or charged on the wrong charger. Only use the maker's charger for the pack, and recycle any pack that is swollen, burnt, leaking, crushed or has been in water.
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    Next steps
    

    Price up the rebuild with the Rebuild or Replace Calculator, and read Is a Battery Pack Rebuild Worth It? first.
    


    

    



    

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