Every cell, live
All cell voltages with min, max and delta, refreshed every few seconds.
Pre-order · ships on 10 November 2026
Your JK BMS, far beyond Bluetooth range: anywhere in the world
The JK app stops at Bluetooth range. JK BMS Monitor reads the BMS over its RS485 port and puts the cells, the balancer and the alarms on your home Wi-Fi and, with the free Cloud, on your phone anywhere in the world.
- Colour screen + Wi-Fi dashboard
- Home Assistant · JSON · Jeedom
- Free Cloud, no subscription
< 0.5 Wpowered by USB-C
0settings written to your battery
€0for the Cloud, forever
10 Novpre-orders ship
JK boards became the default choice for DIY home batteries for good reasons: a strong active balancer, accurate cell measurement, and on the inverter series, proper RS485 and CAN ports to talk to the inverter. Yet most owners still check their pack through Bluetooth, standing next to the cabinet with the app open.
JK BMS Monitor stays connected to the BMS’s RS485 port all the time. It reads each cell, the balancer activity and the temperatures, keeps the curves of the day, sends an e-mail when something trips, and makes all of it available in Home Assistant. No Bluetooth range problem, no phone that must stay in the garage, and nothing written to your BMS settings.
What you get
The balancer at work
See balancing current and which cells it is moving charge between.
Temperatures and MOS
Pack probes and the power MOSFET temperature, logged through the day.
Alarms you will not miss
Cell over- or under-voltage, over-current, temperature and wire resistance warnings, by e-mail.
Home Assistant without ESPHome
Plug in, enter your MQTT broker, done. No soldering an RS485 board onto a dev kit.
Read-only
Your protection parameters stay exactly as you set them in the JK app.
A day in the life of your pack
The dashboard keeps a full day of charge, discharge and state of charge, and alongside it the cell delta. Watch it widen as the pack approaches full, then close as the active balancer catches up. If it no longer closes, it is time to look at that cell.
The free Cloud shows it from anywhere in the world and keeps three years of data to compare seasons and export CSV for your own analysis.
Live dashboardLive
SOC82%
Power-416W
Cell Δ12mV
ChargeDischargeState of charge
Cloud Access · 100% Free
Cloud Access · 100% Free: your battery, live, from anywhere
A JK inverter BMS balances actively, and the interesting part happens at the top of charge, often when you are at work. The free Cloud shows your pack, its cells and the balancing current from your phone, and keeps years of history so you see how the pack really ages.
Live dashboard from anywhere
Every value and every cell, refreshed on their own, on your phone.
Up to 3 years of history
Charge, kWh in and out, temperatures, cell spread, day by day.
An e-mail if it goes quiet
Six hours without news from your box and we tell you.
Public JSON link
Home Assistant, Node-RED, a widget… no port forwarding, no VPN.
CSV export
Everything stored, ready for your spreadsheet.
Installer access
Your installer sees the system without your password; you keep your own access.
€0per month, per year, forever
Optional: your box stays fully local if you prefer. Switch the Cloud on or off in its settings at any time.
How the free Cloud works →JK BMS data in Home Assistant, Jeedom and Node-RED
Cell voltages, balancing state, MOS temperature and cycles become sensors in your smart home. Build automations around the balancer instead of guessing when it runs.
Home AssistantMQTT auto-discovery, no YAML
MQTTReadings published on your broker
JSON APIGET /api.json on your network
JeedomJSON plugin
Node-REDhttp request node
DomoticzHTTP/JSON polling
openHABHTTP binding
IFTTT · MakeThrough the free Cloud JSON link
Ideas people set up first
Let the balancer finish
When the pack reaches full charge with a cell delta above 25 mV, Home Assistant holds the immersion heater off so the charge stays high while the JK balancer works.
MOS temperature watch
If the MOS temperature sensor climbs above 55 °C, a fan on a smart plug starts and a notification tells you the discharge current at that moment.
Spend the surplus
Above 98% with balancing finished, a Shelly relay switches on the water heater until the pack falls back to 90%.
Low cell protection
When the lowest cell drops under 3.05 V, the heaviest loads in the house are turned off before the BMS has to cut the pack.
Your data, your way
The box answers GET /api.json on your network and publishes the same values over MQTT. Home Assistant, Jeedom, Node-RED or your own script read them directly, with no cloud round-trip.
GET http://moniwatt.local/api.json?key=YOUR_KEY
{
"soc": 91, "voltage": 54.42, "current": 6.1,
"cells": [3.402, 3.401, 3.405, 3.398, ...],
"delta_mv": 7, "balancing": true, "balance_current": 0.6,
"mos_temp": 31.0, "temps": [22.4, 22.9], "cycles": 87
}
Up and running in three steps
- PlugThe supplied cable goes into the RS485 port of your JK BMS battery; USB-C into any phone charger.
- ConnectJoin the box’s Wi-Fi from your phone, pick your home network and set a password. No app to install.
- WatchOpen the dashboard in any browser, add it to Home Assistant, and set your alerts.
Made for JK BMS
| Models | JK inverter BMS (RS485 / CAN boards) |
|---|---|
| Connection | RS485 port, RJ45 cable included |
| Your existing wiring | Untouched: the box reads, it never writes |
| Network | Your home Wi-Fi (2.4 GHz); works without internet |
| Integrations | Home Assistant (MQTT auto-discovery), JSON API, Jeedom, Node-RED, Domoticz, openHAB |
| Cloud | Free and optional: live dashboard, 3 years of history, CSV |
| Power | USB-C, under 0.5 W |
Another JK BMS model? Tell us when you order: your box is prepared and tested for it.
Plugs into the RS485 port
JK inverter BMS boards have RJ45 communication sockets for RS485 and CAN. The box connects to an RS485 socket with the supplied cable and is powered by USB-C; its colour screen shows the essentials.
It shares its design with Pylon-Monitor, already monitoring Pylontech batteries across Europe, and uses our RS485 / CAN board with firmware written for the JK protocol.
Designed and assembled in France
Each box is prepared and tested in France before it ships, by the team that makes Pylon-Monitor for Pylontech owners.
Questions before buying? Write to [email protected]: a person answers.
JK BMS Monitor
€49.00
Pre-order price until 9 November 2026 · €59 afterwards
Shipping calculated at checkout
- JK BMS Monitor with colour screen and RS485 / CAN interface
- RJ45 cable for the JK RS485 socket
- USB-C cable
- Free Cloud Access, no subscription
Ships on 10 November 2026 · free cancellation until dispatch
JK BMS app, Wi-Fi dongle or JK BMS Monitor?
What each option really gives you, in short.
| Bluetooth app | Wi-Fi dongle and maker’s cloud | JK BMS Monitor | |
|---|---|---|---|
| Readable from anywhere in the world | — | ✓ | ✓ |
| Keeps working without internet | ✓ | — | ✓ |
| Home Assistant sensors without ESP32 or YAML | — | — | ✓ |
| A screen next to the equipment | — | — | ✓ |
| Never changes a setting | — | — | ✓ |
Stop carrying your phone to the BMS Bluetooth range
Order JK BMS Monitor and read your pack from anywhere in the world, with the free Cloud.
Pre-order for €49Pre-order price · €59 from 10 Nov · ships on 10 November 2026 · free cancellation until dispatch