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esphome-yambms

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Yet another multi-BMS Merging Solution

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# YamBMS ( Yet another multi-BMS Merging Solution )

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> [!TIP]
> This page contains many links to other README.
> If you don't find answers to your questions, [you'll find all the README in this folder](documents/README).

> [!TIP]
> Not sure which YAML to choose ? ... [YamBMS_Remote_Packages_example.yaml](YamBMS_Remote_Packages_example.yaml)
> is a good basis for creating your custom YAML.
> Examples of `BMS`, `Shunt` and `Balancer` packages can be found in the [examples](examples/single-node/) folder.
> You don't have to import a shunt or balancer but you must import at least `one BMS`.
> You can mix different `BMS` models, the only condition is that the `bms_id` are numbered in order starting from `1` !

> [!IMPORTANT]
> YamBMS only allows data merging from your **parallel-connected BMS units** !
> YamBMS **does not work with serial-connected BMS units** !
> YamBMS is not tied to a particular voltage, you can define the number of cells in series in your battery.

> [!IMPORTANT]  
> The most important thing for proper functioning of YamBMS is that **the voltage of your BMS is well calibrated**.
> YamBMS logic is based on the `min_cell_voltage` and `max_cell_voltage` voltages of your `BMS`.
> If you use `YamBMS`, the internal charging logic of the `JK-PB BMS` will not be used.
> Please read the [documentation](README.md#contents) and the [setup instructions](documents/README/Hardware_and_schematic_instructions.md).

| ESPHome application to `combine` information coming from your `BMS / Balancer / Shunt` and adds a smart layer before transmitting instructions to your inverter on `RS485 or CAN bus` using the protocols `PYLON`, `SMA`, `Victron` or `LuxPower` (EG4). | <a href="https://www.buymeacoffee.com/Sleeper85" target="_blank"><img src="https://cdn.buymeacoffee.com/buttons/v2/default-yellow.png" alt="Buy Me A Coffee" style="height: 60px !important;width: 217px !important;" ></a> |
| --- | --- |
| **Note: Pylontech uses 15S/48V and many others uses 16S/51.2V !** Other battery profiles that utilise the **`PYLON`** protocol with different cell counts may also work, e.g. Alpha Ess Smile, BYD Battery-Box LV Flex Lite. Select the correct battery profile in the inverter to match your battery pack ! **DISCLAIMER:** Working with battery systems involves electrical hazards. Please read the complete documentation before installation and use this project at your own risk. | <a href="https://www.buymeacoffee.com/Sleeper85" target="_blank"><img src="images/BMC_QR.png" alt="Buy Me A Coffee" style="height: 217px !important;width: 217px !important;" ></a> |

**Sends over CAN / RS485 bus to your inverter :**
  - Battery Voltage
  - Battery Current (+charge, -discharge)
  - [State of Charge (SoC)](documents/README/YamBMS_behavior.md#state-of-charge) **`SoC 100% will be sent to your inverter only when the battery is fully charged`**
  - State of Health (SoH)
  - Requested Charge Voltage
  - Requested Charge Current
  - Requested Discharge Voltage
  - Requested Discharge Current
  - Min Cell V. and Cell ID
  - Max Cell V. and Cell ID
  - Min temperature and sensor ID
  - Max temperature and sensor ID
  - Battery name
  - Alarms & Warnings

Come and discuss it on the [DIY Solar Forum dedicated topic](https://diysolarforum.com/threads/yambms-jk-bms-can-with-new-cut-off-charging-logic-open-source.79325/).

## Contents

1) [Supported devices](documents/README/Supported_devices.md)
2) [Hardware and schematic instructions](documents/README/Hardware_and_schematic_instructions.md)
3) [YamBMS behavior](documents/README/YamBMS_behavior.md)
4) [YamBMS functions](documents/README/YamBMS_functions.md)
5) [YamBMS charging logic](documents/README/Charging_logic.md)
6) [Installation procedure](documents/README/Installation_procedure.md)
7) [Troubleshooting](documents/README/Troubleshooting.md)
8) [Changelog](documents/README/Changelog.md)

## YamBMS ( Yet another multi-BMS Merging Solution )

![Image](https://raw.githubusercontent.com/Sleeper85/esphome-yambms/main/images/YamBMS_Overview.png "YamBMS Overview")

## Home Assistant dashboard

Available in the [HomeAssistant_Dashboards](HomeAssistant_Dashboards/) folder.

![Image](https://raw.githubusercontent.com/Sleeper85/esphome-yambms/main/images/YamBMS_HA_Dashboard.png "YamBMS HA Dashboard")

## YamBMS Display

> [!TIP]
> Tested with Waveshare ESP32-S3 Touch-LCD 4.3" and 7".

Currently only available for a resolution of **800x480**.

The display can retrieve information in two different ways :

| HA version (recommended) | ESPHome version |
| --- | --- |
| LVGL code executed on a **standalone MCU*** with informations coming from `Home Assistant` (only requires a WiFi connection). This does not overload your **YamBMS MCU***, which already has enough work to do. **Use this YAML =>** [YamBMS_RP_HA_Display.yaml](YamBMS_RP_HA_Display.yaml) | LVGL code executed on the **YamBMS MCU***. In this case, in addition to merging the datas from the `BMS`/`Balancer`/`Shunt` and managing communication with your `inverter`/`charger`, your **YamBMS MCU*** will be overloaded with executing the LVGL display. |

_MCU = an ESP32 / ESP32-S3 / ESP32-P4 / ..._

### YamBMS display

* HA version => [board_options_display_lvgl_package_800x480_blue_navy_ha_yambms.yaml](packages/board/board_options_display_lvgl_package_800x480_blue_navy_ha_yambms.yaml)
* ESPHome version => [board_options_display_lvgl_package_800x480_blue_navy_esphome.yaml](packages/board/board_options_display_lvgl_package_800x480_blue_navy_esphome.yaml)

![Image](https://raw.githubusercontent.com/Sleeper85/esphome-yambms/main/images/YamBMS_Display.png "YamBMS Display")

### YamBMS + Overview display

> [!IMPORTANT]
> You will need to provide datas (non-YamBMS sensors) coming from your `inverter` / `charger`.

* HA version => [board_options_display_lvgl_package_800x480_blue_navy_ha_full.yaml](packages/board/board_options_display_lvgl_package_800x480_blue_navy_ha_full.yaml)

![Image](https://raw.githubusercontent.com/Sleeper85/esphome-yambms/main/images/YamBMS_Display_Overview.png "YamBMS Display Overview")

## Hardware highlighted

This project works with various `ESP32` variants and also with the `Raspberry Pi Pico (RP2040)`.
Note that merging data from multiple BMS, balancers and shunts is resource-intensive, so I highly recommend a board based on the `ESP32-S3` with `PSRAM`.

| [LilyGo T-Connect](documents/README/Board_LilyGo_T-Connect.md) | [Waveshare RS485-CAN](documents/README/Board_Waveshare_ESP32-S3-RS485-CAN.md) | [M5Stack AtomS3R](documents/README/Board_M5Stack_AtomS3.md) |
| --- | --- | --- |
| - ESP32-S3 - 8MB PSRAM - 3x RS485 port - 1x CAN port - 15x GPIOs | - ESP32-S3 - 8MB PSRAM - 1x RS485 port - 1x CAN port - 1x SH1.0 connector - 16x GPIOs | - ESP32-S3 - 8MB PSRAM - 1x BASE port (**for adding RS485/CAN base**) - 1x UNIT HY2.0 port (**for adding RS485/CAN unit**) - 6x GPIOs |
| <img src="images/MCU_ESP32-S3_LilyGo-T-Connect_1.jpg" width="300"> | <img src="images/MCU_ESP32-S3_WS-RS485-CAN_2.png" width="300"> | <img src="images/MCU_AtomS3R.png" width="300"> |

### Single-node

You install `YamBMS` on a single ESP32 connected to your BMS and your inverter.

* Max 3x BMS BLE
* Max 3x BMS UART
* several RS485 BMS on the same bus

### Multi-node

Each BMS/Shunt/Balancer turns into a `modbus server` with its own address.

> [!IMPORTANT]
> The max number of `UART` BMS/Shunt per ESP32 is `2` (unless you use a UART expander) because you need to keep the last `UART` for the `RS485` network.
> The max number of `BLE` BMS/Shunt/Balancer per ESP32 is `2`, ESP32-S3 / AtomS3 can supervise `3` BLE devices.

YamBMS installs on `node1` as a `modbus client` to collect information from all your BMS.
The `node1` is also connected to your inverter via the `CAN bus`.

The BMS/Shunt are connected to other ESP32 nodes connected on a dedicated RS485 bus for YamBMS. Each BMS/Shunt/Balancer becomes a `modbus server`.

The theoretical limit is `256` modbus server (BMS/Shunt) per `RS485 bus` but in reality this will depend on the capabilities of `node1` (YamBMS) which will have to combine all the BMS/Shunt/Balancer together.

[You can find more information about creating your YAML in this How To.](documents/README/YamBMS_RP_YAML.md)

> [!TIP] 
> If you have a lot of `BMS/Shunt/Balancer` to combine, using an `ESP32-S3` or `AtomS3` for `node1` is recommended.

![Image](https://raw.githubusercontent.com/Sleeper85/esphome-yambms/main/images/YamBMS_multi-node_RS485_modbus.png "YamBMS multi-node RS485 modbus")

[@GHswitt](https://github.com/GHswitt) multi-node example :

![Image](https://raw.githubusercontent.com/Sleeper85/esphome-yambms/main/images/YamBMS_multi-node_RS485_modbus_example.png "YamBMS multi-node RS485 modbus example")

> [!NOTE]
> Some boards with integrated `RS485 transceiver` have already a 120 Ohm resistor installed, for example the `LilyGo T-CAN485`, `LilyGo T-Connect` and `LilyGo T-Connect Pro`. 
> If these devices are used in the middle, this resistor must be removed!
> Otherwise transmission errors can occur.

## Try YamBMS with the DEMO firmware

You can simply test the application with a `generic ESP32` without compiling and connecting anything on your ESP32.
The DEMO firmware is composed of `3x BMS` and `1x Shunt` (fake) for a `48V LFP` system.

> [!IMPORTANT] 
> `YamBMS_DEMO_ESP32.factory.bin` is intended for a generic ESP32, does not work with ESP32-S3.
> If you want to test `YamBMS DEMO` with another board you need to compile the firmware with the `YamBMS_RP_DEMO.yaml`.

1) Download [YamBMS_DEMO_ESP32.factory.bin](firmware/YamBMS_DEMO_ESP32.factory.bin)
2) Follow the [procedure explained in this document](https://docs.google.com/document/d/12pOpaG4Iyw3DjC_kB1q0jjBeSKJHK2FvXI1swebL2RI/edit?usp=sharing).

If you want to add a `CAN transceiver` on this `DEMO board` here are the GPIOs to connect it to :
```YAML
tx_pin: 23 # to CAN board CTX
rx_pin: 22 # to CAN board CRX (with 4.7K resistor except for SN65HVD230)
```

## Requirements

* [ESPHome 2026.6.0 or higher](https://github.com/esphome/esphome/releases)
* ESP32 MCU (buying a board with ≥8MB flash is advised if you intend to monitor multiple BMS)
* CAN transceiver (only with TJA1050/TJA1051 => 4.7K resistor for 5V to 3V3 level shifing)
* BMS JK, JBD, Seplos (other BMS brands already integrated with ESPhome can be added easily)
* Inverters supporting CAN PYLON/GoodWe/SMA/Victron Low Voltage protocol
* Optional: 48V to 5V DC-DC converter to power the ESP32 from the JK-BMS VBAT pin (URB4805YMD-10WR3 or VRB4805S-6WR3)
* Optional: JK RS485 adaptor and RS485 to TTL 3V3 adaptor (see schematic section)

## Data collection

> [!NOTE]
> For your information, in January 2026 there were `160` YamBMS users.

If the ESP32 has an internet connection, the following data is sent to [this script](http://script.opentel.be/yambms.post.php)
for statistics collection. Only [@Sleeper85](https://github.com/Sleeper85) have access to this information for the production of statistics, the support and the update service.

- ESP32 MAC address
- YamBMS version
- Board chip
- Board name
- BMS model
- BMS count
- CAN bus name
- CAN bus protocol
- Uptime
- Current date and time

## References

* Thanks to [@syssi](https://github.com/syssi/) for help and developing many BMS components (JK, JBD, Seplos, Pace, etc.).
* Thanks to [@txubelaxu](https://github.com/txubelaxu/) for help and developing the `JK_RS485` component.
* Thanks to [@shvm](https://github.com/shvmm), [@MrPabloUK](https://github.com/MrPabloUK) and [@GHswitt](https://github.com/GHswitt) for their multiple contributions.
* Thanks to [@Fahmula](https://github.com/Fahmula) for developing the `PYLON RS485` component.
* Thanks to [@uksa007](https://www.patreon.com/Uksa007Codedevelopment) for the development of the first CANBUS code.
* Thanks to all the [contributors](https://github.com/Sleeper85/esphome-yambms/graphs/contributors).

esphome-yambms

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