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16 free tools · no signup · nothing leaves your browser

Design a lithium pack that holds up under real load.

Cell Saviors is the tool suite for DIY battery builders — plan the pack, sort your cells, size the BMS and wire, then run it through a validator that tells you what will fail and how to fix it. In plain language, with the safety math shown.

Design a pack in 3D →Validate a design you already have
200+cells in the database
16calculators, all free
100+guides and articles
Live · 7S16P · 21700LayoutVerdictRuntime
7 series groups · 16 cells each · numbered so the layout reads without colourOpen in Designer →
Nominal25.2 V
Energy1 210 Wh
Continuous160 A
Your BMS is the weak point

This pack can pull 160 A continuous. The BMS you picked is rated for 30 A — size up or limit the controller.

Estimate — not certificationEdit anything in the tools and the numbers move. No account, no save required.

16 tools, four questions

What am I building · will it hold · what parts do I need · where do I look it up.

All tools →

What am I building?

Pack PlannerUse this when you know the device, not the pack.3D Pack DesignerUse this when you need real dimensions and a layout.STL GeneratorUse this when you want printable holders and enclosures.Powerwall PlannerUse this when the pack is part of a whole power system.

Will it hold up?

Pack Design ValidatorUse this before you weld — pass, warning, or fail.Runtime SimulatorUse this to see real runtime under your actual load.Thermal & Layout VisualizerUse this to find hotspots and spacing problems.Cell Resistance EstimatorUse this to test cells before trusting them.Safety Checklist GeneratorUse this as the last step before you power on.

What parts do I need?

Pack BuilderUse this to balance the cells you already own.BMS PickerUse this to match a BMS to your cell count and current.Wire Resistance CalculatorUse this to size wires for high-current runs.Car Audio CalculatorUse this when you are going lithium for car audio.Cost vs Performance OptimizerUse this to compare cost per kWh across cells.

Where do I look it up?

Cell DatabaseSpecs and tested ratings for hundreds of cells.Essential Tools & SuppliesThe gear we actually use, one honest pick per category.
Why trust the numbers

Safety first, without the lecture.

Every result shows the assumption behind it, and every warning tells you what's wrong, why it matters, and how to fix it. We'd rather you close the tab annoyed than build something that vents.

Estimates, never certificationSources cited
Real datasheet ratings, not marketing numbers

Cell specs come from manufacturer datasheets and Mooch's independent tests, with the test conditions attached.

Warnings are the loudest thing on the screen

A failing check outranks the pretty layout, sits next to the input that caused it, and never gets collapsed away.

Your build stays yours

Projects save in your browser. Sharing anything is a deliberate, reversible choice.

Latest from the workshop

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Mar 28, 2026
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Can You Use PLA for 3D-Printed Battery Frames?
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PLA starts to soften around 60°C, but that does not automatically make it unusable for battery frames. In many well-designed packs, the welded cells, enclosure, and overall fitment provide the rigidity, making PLA a workable option even if PETG or higher-temp materials are better choices.

Mar 10, 2026
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Essential tools & supplies

The spot welders, testers, nickel strip and safety gear we actually use — one honest pick per category.

Spot weldersCell testersNickel & busbarSafety gear

New tools and build tips

An email when we ship a tool, add cells to the database, or publish a guide worth your time. Nothing else.

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