4 layers260 × 113 mm
4 layers44 × 72.1 mm
Precharge
cellkeeper-bms/cellkeeper-hardware11PCB for the CellKeeper BMS
- Size
- 44 × 72.1 mm
- Copper layers
- 4
- Thickness
- 1.6 mm
- Parts
- 8
- Nets
- 5
- Pads
- 30
- Tracks, vias
- 4, 0
- Pours
- 5
- Routed
- Yes
- KiCad
- KiCad 10.0 (file 20260206)
- Created
- 3 Dec 2025
- Updated
- 28 Oct 2026
Overview
Precharge is an open-source printed circuit board by cellkeeper-bms, from the cellkeeper-bms/cellkeeper-hardware repository on GitHub, published under the GPL-3.0 licence. It is a 4-layer board of 44 × 72.1 mm with 8 parts on 5 nets, routed with 4 tracks and 0 vias.
It is built around the B59451C1130B070. It belongs with the power boards of this library.
Main components
1README
README.mdCellKeeper BMS — v1.1
KiCad PCB design for the CellKeeper Battery Management System, a replacement BMS controller for battery packs using the isoSPI protocol. The main board fits the Tesla battery's penthouse: the pack's original harness, HV sense, shunt and BMB connectors plug into it, and it mounts on the original brackets.
Each ordered revision has a release with its Gerbers, JLCPCB BOM and CPL, schematic PDF, board PDF (3D views and 1:1 prints) and the enclosure print files. Rev 1.1 was ordered on 2026-10-28; work towards rev 1.2 is on the rev1.2 branch.
Overview
- MCUs: two Raspberry Pi RP2354B (dual Cortex-M33, 2 MB in-package flash): the main BMS controller and an independent supervisor, linked by UART. The supervisor also sees the isoSPI receive line and the E-stop input, and it alone enables the contactor drivers.
- Current sensing: TI INA228 (20-bit) on a galvanically isolated domain (ISO1540 I2C isolator, isolated 5 V DC-DC), also reading the shunt's temperature.
- HV sensing: 6 sense points (BAT±, LINK±, FC±) through 501:1 dividers into two ADS1115 ADCs: pack, link and output voltage, and the voltage across each contactor.
- BMB communication: transformer-isolated isoSPI master (SP3485 driver, AM26LV32 receiver, HM2113 transformer), Manchester-encoded by the RP2354's PIO.
- CAN: two ISO1050 interfaces: inverter CAN, isolated with its own DC-DC, on an RJ45 shared with the E-stop and aux lines; and inter-BMS CAN2 on a pass-through RJ45 pair (not isolated).
- Contactors: four low-side drivers (FC+, FC-, Link+, Link-): BSC0805LS MOSFETs and UCC27524 gate drivers, PWM'd by the firmware to economise the hold current. The contactor supply is sensed.
- Supply: 13–16 V logic and contactor inputs (separate, both sensed), TPS5430 5 V buck and 3.3 V LDO; chassis ground terminal.
- HV battery: 400 V nominal.
- USB-C ×3: BMS, supervisor, and HMI link. The HMI link is not for a computer: it powers an external ESP32 display (5 V 1 A) and carries its serial.
- I/O: E-stop input (optocoupler; jumper JP37 disables it), an extra opto input and two extra outputs, fast-charge contactor aux-contact inputs for weld detection, SX serial interface, and experimental PCS signals on jumpers.
- Board revision strap on GPIO47 (ADC7).
Repository Contents
Three boards, each its own KiCad project. They share no copper: the hat and the precharge board connect to the rest of the system by wires and lugs.
| Path | Description |
|---|---|
CellKeeper/ | Main controller board (CellKeeper.kicad_pro). Each ordered revision's Gerbers, BOM, CPL, schematic and board PDFs are on the releases page |
isoSPI-Hat/ | isoSPI hat for a Raspberry Pi Pico: SP3485 / AM26LV32 / HM2113 transformer to the BMB connector |
Precharge/ | Precharge board: six PTCs (three parallel strings of two) between M8 lugs, plus the HV system wiring diagram |
lib/ | Shared CellKeeper_Local symbol and footprint libraries and CellKeeper.3dshapes 3D models |
enclosure/ | 3D-printable case for the main board (build123d) |
graphics/ | Silkscreen artwork and README images |
python_scripts/ | README renders (render_readme_images.py), release files (export_release_files.py), 3D model generators |
docs/ | How to release a revision (releasing.md), README notes |
Enclosure
A two-part printed case (base tray and lid) for the main board, generated by
enclosure/cellkeeper_case.py. It mounts in the penthouse on the original HVC brackets. The lid
carries the logo and connector labels, which can be printed as a contrasting-colour inlay, with
open tunnels over the LEDs. Ready-to-print STEP and STL files are attached to each
release; running the script writes
them to enclosure/output/print/.
The board shows the case in KiCad's 3D viewer through the ENC1 footprint.
Safety
⚠️ This board interfaces with 400 V battery packs that can deliver lethal current. Only qualified personnel should work on high-voltage systems. This is a v1.1 development design — untested, no warranty, use at your own risk.
Acknowledgments
- Damien Maguire & Tom de Bree — Original BATMan BMS software
License
GPL-3.0 — see LICENSE.
Parts
8| Qty | Value | Footprint | References |
|---|---|---|---|
| 6 | B59451C1130B070 | CellKeeper_Local:BMS_Library__RV_Disc_D15.5mm_W7.5mm_P5.0mm | TH1, TH2, TH3, TH4, TH5, TH6 |
| 2 | MountingHole_Pad | CellKeeper_Local:MountingHole__MountingHole_8.4mm_M8_Pad_Via | H1, H2 |
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Questions
How big is the Precharge PCB?
It measures 44 × 72.1 mm and has 4 copper layers, 1.6 mm thick.
What parts does the Precharge use?
8 parts, built around the B59451C1130B070. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.
Where can I download the Precharge KiCad files?
From the cellkeeper-bms/cellkeeper-hardware repository on GitHub, at the commit this page was made from: the board is Precharge/Precharge.kicad_pcb and its schematic CellKeeper/CellKeeper.kicad_sch. PCBKit opens the board in the browser, with nothing to install.
Can I use the Precharge design in my own project?
Its repository publishes it under the GPL-3.0 licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).