Balance your cells into even series groups based on capacity and internal resistance. Paste your cell data and get an optimized layout.
Select cell condition and balancing method, then paste or upload your values.
Paste your measured values — a 14S4P pack needs 56 cells.
CSV import is client-side. Your builder inputs stay in this browser until you clear them.
Set pack dimensions and voltage assumptions before generating groups.
Paste cell values, set the pack dimensions, and hit Generate pack. Nothing you enter leaves this browser.
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. Not sure which cells to use? Browse the cell database and compare specs before you source.
Once your groups are balanced here, our step-by-step 18650 build guide covers welding, BMS wiring, wrapping, and testing the finished pack.
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.
It takes your measured cells and sorts them into series groups so every parallel group ends up with a matching total capacity. That keeps the pack balanced so the weakest group does not drag down the whole pack.
In a series pack every group carries the same current, so the lowest-capacity group reaches empty first and caps how much of the pack you can actually use. Matching total capacity across groups maximizes usable range and cycle life.
Where you can, yes. Higher-resistance cells run hotter and sag more under load. Grouping by both capacity and internal resistance keeps heat and voltage even across the pack.
Test each cell with a charger or analyzer for capacity, and measure resistance with a cell tester or our internal resistance calculator. Paste the values in and the builder groups them for you.
You can if they share the same chemistry and voltage range, but keep each parallel group internally matched. Mixing very different capacities or ages within a group ages the pack unevenly; the builder helps by balancing group totals.
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