Battery Building Tools Build & Match

18650 Battery Pack Builder

Balance your cells into even series groups based on capacity and internal resistance. Paste your cell data and get an optimized layout.

Step 1

Load clean cell data

Paste values or import a CSV, then choose whether you are balancing by capacity, IR, or both.

Step 2

Set the target pack

Decide on your series and parallel count, then confirm the voltage assumptions for the finished pack.

Step 3

Review and export

Inspect divergence, leftovers, and per-group values before you start physically assembling cells.

Target pack14S4P

Cells required56

Entries pasted0

1Cell data & balancing

Cells usedSalvaged cellsNew cells

Balancing method

Cell capacities

Use capacity values only to balance each series group.

Cell capacities with IR

Use capacity plus internal resistance together when assigning cells.

Internal resistance only

Balance purely by internal resistance values.

Enter a comma-separated list of cell capacities. Example: 3124,3110,3098,3088

CSV import is client-side. Your builder inputs stay in this browser until you clear them.

Make sure that you test and grade your salvaged cells prior to using them in a build. If you haven't tested your cells yet, these are the best 18650/21700 cell testers on the market.

If you notice any issues with IR balancing, please leave us a note via our contact page and we will get back to you as soon as we can.

Number of seriesCells in parallelNominal cell voltageMinimum cell voltageMaximum cell voltage

2Pre-build checks

Cell count check

You are short 56 cells for the requested 14S4P pack.

Extra cells

No spare cells beyond the requested pack size.

Balancing mode

Capacity-only balancing is fastest and usually enough for consistent new cells.

Tips for building a better pack

Make sure that you test and grade your salvaged cells prior to using them in a build. If you haven't tested your cells yet, these are the best 18650/21700 cell testers on the market.

If you're building a pack that will be handling higher amperage we recommend checking out this article to see if using copper and nickel will be best for your build.

If you enjoyed building your battery pack, imagine how much you could enjoy building your own DIY lithium ion charger. It can be just as rewarding as finishing a pack so if it sounds interesting to you, we strongly suggest you give it a shot.