4 layers193.5 × 105 mm BMU v1, the printed circuit board in 3D

BMU v1

KomplexKapharnaum/KXKM_Batterie_Parallelator

Battery Management Unit for parallel 24-30V packs Up to 32 batteries ESP32-S3 BLE + MQTT + InfluxDB iOS companion app

Size: 193.5 × 105 mm
Copper layers: 4
Thickness: 1.6 mm
Parts: 143
Nets: 105
Pads: 438
Tracks, vias: 1,042, 474
Pours: 221
Routed: Yes
KiCad: KiCad 8.0 (file 20240108)
Created: 27 Nov 2024
Updated: 6 Nov 2026

Overview

BMU v1 is an open-source printed circuit board by KomplexKapharnaum, from the KomplexKapharnaum/KXKM_Batterie_Parallelator repository on GitHub, published under the GPL-3.0 licence. It is a 4-layer board of 193.5 × 105 mm with 143 parts on 105 nets, routed with 1,042 tracks and 474 vias.

It is built around the VPS8505, ISO1540DR-HXY and TCA9517ADGK, with the TCA9535PWR(UMW), 1N4148W and HOVB4026-5W-2MR-1% among its other parts. Its parts include 43 resistors, 24 diodes, 20 capacitors, 9 ICs and 5 connectors.

Main components

README

README.md

BMU v1 on the test bench with six battery packs

BMU v2 PCB (3D render)

KXKM Batterie Parallelator

Battery Management Unit for parallel 24-30V packs
Up to 32 batteries · ESP32-S3 · BLE + MQTT + InfluxDB · iOS companion app

Overview

The KXKM Batterie Parallelator is an embedded Battery Management Unit (BMU) that safely parallels multiple battery packs (24-30V) for off-grid stage installations. Each battery is individually monitored (voltage, current, temperature) and can be disconnected in microseconds via MOSFET switches.

Built by L'Electron Rare for KompleX KapharnaüM (Villeurbanne, France) — a live arts company deploying digital scenography in public spaces without grid power.

Key Features

Feature	Description
Per-battery protection	Under/over-voltage, over-current, imbalance detection
Auto-reconnection	Exponential backoff with permanent lock after 5 faults
Soft-balancing	Duty-cycling with opportunistic R_int measurement
Victron integration	BLE Instant Readout + GATT SmartShunt emulation + device scanner
Touchscreen UI	320x240 LVGL display with battery grid, SOH, charts
iOS companion app	BLE real-time monitoring, offline cache, role-based access
Cloud telemetry	MQTT + InfluxDB + Grafana with offline persistence
OTA updates	Dual-partition with automatic rollback

Quick Start

bash

# ESP-IDF firmware (production)
cd firmware-idf
source ~/esp/esp-idf/export.sh
idf.py build
idf.py -p /dev/cu.usbmodem* flash monitor

# PlatformIO (legacy Arduino)
pio run -e kxkm-s3-16MB --target upload

# Run all tests (no hardware needed)
pio test -e sim-host          # 13 PlatformIO tests
cd firmware-idf && idf.py build  # 13 ESP-IDF host tests

# Cloud stack (kxkm-ai server)
cd kxkm-api && cp .env.example .env && docker compose up -d

Architecture

text

                          ┌──────────────────────────┐
                          │    ESP32-S3-BOX-3         │
                          │    320x240 LVGL display   │
                          │    NimBLE + WiFi          │
                          └─────────┬────────────────┘
                                    │ I2C 50kHz
                    ┌───────────────┼───────────────┐
                    │               │               │
              ┌─────▼─────┐  ┌─────▼─────┐  ┌─────▼─────┐
              │ TCA9535    │  │ TCA9535   │  │  ...×8    │
              │ 4× MOSFET  │  │ 4× LED   │  │           │
              └─────┬─────┘  └───────────┘  └───────────┘
                    │
              ┌─────▼─────┐
              │ INA237 ×4  │  ← per TCA (voltage + current)
              └───────────┘

    ┌──────────────────────────────────────────────────────┐
    │                    Cloud Stack                        │
    │  BMU ──MQTT──► Mosquitto ──► Telegraf ──► InfluxDB   │
    │                                              │       │
    │  iPhone ◄──BLE──► BMU    Grafana ◄───────────┘       │
    │  iPhone ◄──REST──► FastAPI ◄─────────────────┘       │
    └──────────────────────────────────────────────────────┘

Firmware Components (ESP-IDF, 25 modules)

Component	Role
`bmu_protection`	State machine: 5 states, 5 criteria, permanent lock
`bmu_balancer`	Soft-balancing duty-cycling + R_int measurement
`bmu_ina237`	16× INA237 power monitors (2mΩ shunt)
`bmu_tca9535`	8× GPIO expanders (switches + LEDs)
`bmu_ble`	NimBLE 4 GATT services + Victron SmartShunt
`bmu_ble_victron`	Victron Instant Readout (AES-CTR encrypted ads)
`bmu_ble_victron_scan`	BLE central scanner for Victron devices
`bmu_display`	LVGL: battery grid, pack info, SOH, charts, swipe
`bmu_influx` + `_store`	InfluxDB client + offline FAT/SD persistence
`bmu_mqtt`	ESP-MQTT with auth credentials
`bmu_vedirect`	Victron VE.Direct UART parser (solar charger)
`bmu_rint`	Internal resistance pulse measurement
`bmu_web`	HTTP + WebSocket with token auth + rate limiting
`bmu_config`	NVS runtime config + Victron device keys
`bmu_storage`	NVS, FAT, SPIFFS, SD card, USB MSC
`bmu_ota`	OTA firmware update with rollback

Protection Logic

text

Nb_switch < 5   →  Reconnect immediately when condition clears
Nb_switch == 5  →  10-second delay before reconnection
Nb_switch > 5   →  Permanent lock (blinking red LED) until reboot

Threshold	Default	Configurable
Min voltage	24,000 mV	via Kconfig + NVS
Max voltage	30,000 mV	via Kconfig + NVS
Max current	10,000 mA	via Kconfig + NVS
Imbalance	1,000 mV	via Kconfig + NVS
Reconnect delay	10,000 ms	via Kconfig
Switch limit	5	via Kconfig

LED Behavior

State	LED
Connected	Solid green
Disconnected	Solid red
Error	Blinking red (~1 Hz)
Locked	Solid red

iOS Companion App

KXKM BMU — SwiftUI + CoreBluetooth

Feature	Transport
Real-time battery dashboard	BLE (2s poll)
Battery detail + voltage chart	BLE
Switch ON/OFF + reset	BLE (role-gated)
Protection config (0.025V/A step)	BLE
WiFi config for BMU	BLE
Audit trail + filtering	Local SQLDelight
Offline mode with cache indicator	Auto-fallback
SOH dashboard + R_int	BLE + REST
Victron device scanning	BLE passive

3 roles: Admin (full), Technician (control), Viewer (read-only) — PIN + Face ID.

Code: iosApp/ (Xcode, CoreBluetooth) + kxkm-bmu-app/ (KMP Shared Kotlin)

Victron BLE Integration

The BMU interacts with the Victron ecosystem via three mechanisms:

Mechanism	Direction	Protocol
Instant Readout	BMU → VictronConnect	AES-CTR encrypted advertising (PID 0xA389)
GATT SmartShunt	BMU → any BLE client	9 read-only characteristics (V, I, SOC, Ah, TTG, T, alarm)
Device Scanner	Victron devices → BMU	Passive BLE scan, AES decrypt, 8 device cache

Supported Victron record types: Solar (0x01), Battery (0x02), Inverter (0x03), DC-DC (0x04).

Cloud Infrastructure

Docker stack on kxkm-ai server:

Service	Port	Role
Mosquitto	1883, 9001	MQTT broker (authenticated)
InfluxDB 2.7	8086	Time-series storage (org=kxkm, bucket=bmu)
Telegraf	-	MQTT → InfluxDB bridge
FastAPI	8400	REST API (sync, history, audit)
Grafana 11	3001	3 dashboards (live, fleet, solar)

Setup: cp .env.example .env — fill all secrets (API key, InfluxDB token, MQTT credentials, Grafana password, CORS origins). All secrets via ${...} env vars, chmod 600 .env.

Offline resilience: when WiFi/InfluxDB is unreachable, telemetry is persisted to internal FAT flash (/fatfs/influx/) with 2-file rotation (512KB each). Automatic replay on reconnection.

Testing

26 tests total — no hardware required.

PlatformIO sim-host (13 tests)

bash

pio test -e sim-host

Suite	Tests	Covers
`test_protection`	10	V/I/imbalance/lock state machine
`test_battery_route_validation`	-	Index bounds + state checks
`test_influx_buffer_codec`	-	InfluxDB line-protocol encoding
`test_web_mutation_rate_limit`	3	Sliding window + multi-IP
`test_web_route_security`	9	Constant-time token + Bearer
`test_ws_auth_flow`	7	Combined auth + rate limit
`test_mqtt_influx_codec`	3	JSON MQTT + topic parsing
`test_emulation_bench`	-	Emulation benchmark

ESP-IDF Host Tests (13 tests)

bash

cd firmware-idf && idf.py build

Suite	Tests	Covers
`test_protection`	13	Full state machine (ESP-IDF)
`test_victron_gatt`	8	GATT encoding (V, SOC, alarm, TTG, T)
`test_victron_scan`	5	Payload parsing, expiry, MAC, CID
`test_ble_victron`	-	Battery/solar payload encoding
`test_vedirect_parser`	-	VE.Direct frame parsing
`test_rint`	-	R_int calculation
`test_config_labels`	-	Battery label management
`test_vrm_topics`	-	VRM topic generation

CI/CD Pipelines

Pipeline	Trigger	Gate
`ci.yml`	push/PR	sim-host 13 tests pass
`sim-host-tests.yml`	push/PR	+ S3 build + RAM ≤75% + Flash ≤85%
`esp-idf-ci.yml`	push/PR	+ ESP-IDF host tests + flash ≤85% of 2MB OTA

Current flash usage: 81% (1.69 MB / 2 MB OTA partition) — 19% headroom.

Security Audit

All findings resolved as of 2026-04-07.

Phase 1 — Migration (March 2026): 7/7 resolved

ID	Finding	Status
CRIT-001	Obsolete function calls	✅
CRIT-002	Unreliable global Nb_INA	✅
CRIT-003	I2C access without mutex	✅
CRIT-004	Missing mutex init	✅
HIGH-005	WebSocket V/I race	✅
HIGH-006	reconnect_time race	✅
HIGH-007	Uninitialized globals	✅

Phase 2 — Deep audit (March-April 2026): 13/13 resolved

ID	Severity	Finding	Fix
CRIT-A	Critical	mV/V unit mismatch	ESP-IDF: mV everywhere
CRIT-B	Critical	Imbalance vs config instead of fleet max	bmu_protection
CRIT-C	Critical	Deadlock in web switch	bmu_web
CRIT-D	Critical	Unauthenticated routes	bmu_web_security
HIGH-1	High	Negative overcurrent ignored	Bidirectional factor
HIGH-2	High	Unauthenticated WebSocket	Token on first frame
HIGH-3	High	XSS in /log	cJSON null check
HIGH-4	High	MQTT plaintext	Mosquitto auth + .env
HIGH-5	High	I2C speed change unguarded	I2CLockGuard
HIGH-7	High	Public battery_voltages[]	state_mutex
HIGH-8	High	Influx task crash on SD fail	influx_store fallback
MED-1	Medium	No permanent lock (F08)	BMU_STATE_LOCKED
MED-010	Medium	mV/V harmonization	mV throughout

Infrastructure audit (April 2026): 5/5 resolved

Finding	Fix
Mosquitto anonymous access	Auth + password file
Hardcoded secrets in docker-compose	All via .env (chmod 600)
Default InfluxDB token	Rotated (44-char random)
CORS allow_origins=["*"]	Restricted via env var
Offline data loss	FAT/SD persistence + replay

Hardware

PCB Revisions

Version	Status	Files
BMU v1	Manufactured	`hardware/PCB/`
BMU v2	Production-ready (ERC 0, BOM 107)	`hardware/pcb-bmu-v2/`

Key ICs

IC	Package	Role	I2C Address
INA237	VSSOP-10	Power monitor (V/I/P)	0x40-0x4F (16 max)
TCA9535	TSSOP-24	GPIO expander (switches + LEDs)	0x20-0x27 (8 max)
ISO1540	SOIC-8	Galvanic I2C isolator	-
IRF4905	D2PAK	P-channel MOSFET (55V, 74A)	-

I2C Mapping

text

TCA_0 (0x20) → INA 0x40-0x43 → Batteries 1-4
TCA_1 (0x21) → INA 0x44-0x47 → Batteries 5-8
TCA_2 (0x22) → INA 0x48-0x4B → Batteries 9-12
TCA_3 (0x23) → INA 0x4C-0x4F → Batteries 13-16

Topology constraint: Nb_TCA × 4 == Nb_INA — mismatch triggers fail-safe (all OFF).

Project Structure

text

KXKM_Batterie_Parallelator/
├── firmware-idf/          # ESP-IDF 5.4 firmware (25 components)
│   ├── components/        # Modular ESP-IDF components
│   ├── main/              # app_main entry point
│   └── test/              # Unity host tests (13 suites)
├── firmware/              # Legacy PlatformIO/Arduino firmware
│   ├── src/               # Source modules
│   ├── test/              # sim-host tests (8 suites, 13 tests)
│   └── lib/INA237/        # Local INA237 driver fork
├── iosApp/                # iOS SwiftUI app (CoreBluetooth)
├── kxkm-bmu-app/          # KMP shared Kotlin module
│   └── shared/            # Cross-platform domain logic
├── kxkm-api/              # Docker stack (Mosquitto, InfluxDB, FastAPI, Grafana)
├── hardware/              # KiCad schematics + Gerbers (v1 + v2)
├── specs/                 # Kill_LIFE gates (S0-S3)
├── docs/                  # Specs, plans, governance, research
├── grafana/dashboards/    # 3 Grafana dashboard JSONs
└── scripts/               # CI, QA, ML pipeline

About KompleX KapharnaüM

KompleX KapharnaüM is a live arts company based in Villeurbanne (Lyon, France), active for 20+ years in street arts, live performance, and digital creation. The company develops its own embedded hardware platform (K32, ESP32-based) and maintains open-source tools on GitHub.

License

GNU General Public License v3.0

_{Built with ESP-IDF, LVGL, NimBLE, SwiftUI, FastAPI, InfluxDB, and Grafana.}
_{Developed by L'Electron Rare for KompleX KapharnaüM}

Project files

Show this board on your page

https://pcbkit.io/boards/KomplexKapharnaum/KXKM_Batterie_Parallelator

The board's own page, for a message or a post.

Source

Repository: KomplexKapharnaum/KXKM_Batterie_Parallelator
Board file: hardware/PCB/BMU v1/BMU v1.kicad_pcb
Commit: 6cc96ed
Licence: GPL-3.0

Parts

143

Qty	Value	Footprint	References
19	SolderJumper_3_Open	Jumper:SolderJumper-3_P1.3mm_Open_RoundedPad1.0x1.5mm_NumberLabels	JP2, JP3, JP4, JP5, JP6, JP10, JP11, JP12, JP13, JP14, JP15, JP16, JP17, JP18, JP19, JP20 +3
10	0.1uF	Capacitor_SMD:C_0805_2012Metric	C2, C3, C4, C5, C6, C7, C8, C9, C10, C11
8	10R	Resistor_SMD:R_0603_1608Metric	R3, R4, R10, R11, R17, R18, R37, R38
8	1N4148W	Diode_SMD:D_SOD-523	D2, D3, D6, D7, D10, D11, D14, D15
8	330R	Resistor_SMD:R_0603_1608Metric	R29, R30, R31, R32, R33, R34, R35, R36
8	470R	Resistor_SMD:R_0603_1608Metric	R2, R5, R9, R12, R16, R19, R23, R39
8	MountingHole_Pad	MountingHole:MountingHole_5mm_Pad	H1, H2, H3, H4, H5, H6, H7, H8
5	MountingHole	MountingHole:MountingHole_3.2mm_M3_DIN965	H9, H10, H13, H13, H14
4	10k	Resistor_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P5.08mm_Horizontal	R7, R14, R21, R41
4	470R	Resistor_THT:R_Axial_DIN0204_L3.6mm_D1.6mm_P5.08mm_Horizontal	R6, R13, R20, R40
4	BLUE	LED_SMD:LED_0603_1608Metric	D4, D8, D12, D16
4	GREEN	LED_SMD:LED_0603_1608Metric	D21, D23, D25, D27
4	HOVB4026-5W-2MR-1%	easyeda2kicad:RES-SMD_4P-L10.8-W6.7	R1, R8, R46, R47
4	INA237	Package_SO:VSSOP-10_3x3mm_P0.5mm	U1, U2, U3, U7
4	IRFZ44NPBF	Package_TO_SOT_THT:TO-220-3_Horizontal_TabUp	Q5, Q6, Q7, Q8
4	RED	LED_SMD:LED_0603_1608Metric	D20, D22, D24, D26
3	10uF	Capacitor_SMD:C_0805_2012Metric	C14, C20, C21
3	1A/100V	Diode_SMD:D_SMA	D5, D18, D19
2	10uF/50V	Capacitor_SMD:C_1206_3216Metric	C15, C16
2	1K	Resistor_SMD:R_0603_1608Metric	R26, R27
2	50R	Resistor_SMD:R_0603_1608Metric	R24, R25
2	MountingHole_Pad	MountingHole:MountingHole_3.2mm_M3_Pad_Via	H11, H12
2	RJ45_Shielded	easyeda2kicad:RJ45-TH_RC01061	J1, J2
2	Screw_Terminal_01x01	easyeda2kicad:TH-8_L20.0-W16.0-P5.60_AMT0860001TA0000G	J11, J12
1	0,1uF	Capacitor_SMD:C_0805_2012Metric	C13
1	0.1uF	Capacitor_SMD:C_0603_1608Metric	C18
1	10K	Resistor_SMD:R_0603_1608Metric	R28
1	10k/1%	Resistor_SMD:R_0603_1608Metric	R22
1	10uF,16V	Capacitor_SMD:CP_Elec_8x10	C1
1	1N4148WT	Diode_SMD:D_SOD-523	D9
1	1uF	Capacitor_SMD:C_0805_2012Metric	C12
1	20pF	Capacitor_SMD:C_0603_1608Metric	C19
1	22uH,1.5A	Inductor_SMD:L_Taiyo-Yuden_NR-50xx	L1
1	52.3k/1%	Resistor_SMD:R_0603_1608Metric	R15
1	Conn_01x02_Pin	Connector_PinHeader_2.54mm:PinHeader_1x02_P2.54mm_Vertical	J3
1	ISO1540DR	Package_SO:SOIC-8_3.9x4.9mm_P1.27mm	U5
1	LOGO	LOGO	G***
1	MCP16331T-E/CH	Package_TO_SOT_SMD:SOT-23-6	U10
1	SolderJumper_2_Open	Jumper:SolderJumper-2_P1.3mm_Open_RoundedPad1.0x1.5mm	JP1
1	TCA9517ADGK	easyeda2kicad:VSSOP-8_L3.0-W3.0-P0.65-LS5.0-BL	U4
1	TCA9535PWR	Package_SO:TSSOP-24_4.4x7.8mm_P0.65mm	U6
1	VPS8505	easyeda2kicad:SOT-23-6_L2.9-W1.6-P0.95-LS2.8-BR	U8
1	VPT85BB-01A	Transformer_SMD:VP85BB-01A	TR1

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Questions

How big is the BMU v1 PCB?

It measures 193.5 × 105 mm and has 4 copper layers, 1.6 mm thick.

What parts does the BMU v1 use?

143 parts, built around the VPS8505, ISO1540DR-HXY, TCA9517ADGK and TCA9535PWR(UMW). 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 BMU v1 KiCad files?

From the KomplexKapharnaum/KXKM_Batterie_Parallelator repository on GitHub, at the commit this page was made from: the board is hardware/PCB/BMU v1/BMU v1.kicad_pcb and its schematic hardware/PCB/BMU v1/BMU v1.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the BMU v1 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).

Overview

Main components

VPS8505

ISO1540DR-HXY

TCA9517ADGK

TCA9535PWR(UMW)

1N4148W

HOVB4026-5W-2MR-1%

IRFZ44NPBF

1N4148WT

VPT85BB-01A

README

KXKM Batterie Parallelator

Overview

Key Features

Quick Start

Architecture

Firmware Components (ESP-IDF, 25 modules)

Protection Logic

LED Behavior

iOS Companion App

Victron BLE Integration

Cloud Infrastructure

Testing

PlatformIO sim-host (13 tests)

ESP-IDF Host Tests (13 tests)

CI/CD Pipelines

Security Audit

Hardware

PCB Revisions

Key ICs

I2C Mapping

Project Structure

About KompleX KapharnaüM

License

Parts

More from KomplexKapharnaum/KXKM_Batterie_Parallelator

Similar boards

Questions

How big is the BMU v1 PCB?

What parts does the BMU v1 use?

Where can I download the BMU v1 KiCad files?

Can I use the BMU v1 design in my own project?