// the take
A DIY battery management system for lithium-ion packs, built around per-cell monitoring boards and an ESP32 (or legacy ESP8266) controller with CANBUS/RS485/SD logging. This repo is hardware only — KiCad schematics, PCB layouts, gerbers and BOMs; the firmware lives in two separate repos. Aimed at people building their own powerwall or EV-salvage battery packs who are comfortable soldering 0805-size parts and flashing microcontrollers.
Genuinely mature hardware line — five module revisions (V400 through V490) show real iteration based on field feedback, like adding an external crystal to fix low-voltage reliability or moving to ATTINY1624 for smaller/cheaper boards. Every design ships with a full BOM, JLCPCB-ready gerbers and pick-and-place files, so you can order boards without touching KiCad. The all-in-one V490 module consolidates 8-16S monitoring onto one board instead of one board per cell, which cuts wiring and cost for larger packs. Active community on the OpenEnergyMonitor forum and a YouTube build series mean you're not debugging alone.
This is hardware-only — to get a working BMS you also need to pull firmware from two other repos (diyBMSv4ESP32 or the legacy diyBMSv4Code) and get versions aligned yourself. The license is CC BY-NC-SA, non-commercial: fine for a hobby build, a dead end if you wanted to sell assembled units or integrate it into a commercial product. Several module revisions are explicitly legacy (V400, V421, V440) but still sit in the repo with no clear deprecation markers beyond a README note, so it's easy to order the wrong one. It's also a DIY high-voltage/high-current safety system with no warranty and an explicit "don't use this for safety-critical systems" disclaimer — balancing current, fusing and thermal design are all on you to validate before it goes near a real pack.
We read the README, the directory tree and a key source file in October 2026. Nobody pays to be listed. How we judge →