What a BMS does and why communication with the inverter matters

September 29, 2026 · 5 min read · Danilo Nascimento

Learn what a lithium battery BMS does, how it talks to the inverter and what changes with or without communication. Simulate its limits in the calculator.

What a BMS is

The BMS (Battery Management System) is the electronics that looks after a lithium battery. It measures each cell and acts if anything leaves the safe limit. In ready-made rack batteries the BMS is already inside the case.

Protection

safety

It switches the battery off on overvoltage, undervoltage, overcurrent, short circuit and temperature out of range.

Balancing

lifetime

It equalizes the charge of the cells, so the weakest does not limit the others or get overcharged.

Measurement

information

It measures voltage, current and temperature and estimates the battery’s state of charge (SoC) and health (SoH).

Communication

integration

It tells the inverter the current limits and the charge voltage, and receives the charge and discharge commands from it.

What the BMS protects against

	Charging	Discharging
High cell voltage	Blocks charging	No effect
Low cell voltage	No effect	Blocks discharging
Low temperature	May block (e.g. LiFePO4 below 0 °C; each model has its own limit)	Reduces the current
High temperature	Reduces or blocks	Reduces or blocks
Overcurrent or short circuit	Switches off	Switches off

✓ no effect · ◐ limits · ✗ blocks

The conversation between battery and inverter

Besides the power cables there is a communication cable, usually CAN or RS485. Through it the BMS tells the inverter how much it can charge and discharge at that moment, and the inverter obeys.

Batterywith BMS
limits and state
CommunicationCAN or RS485
commands
Inverterfollows the limits
Home

The BMS reports what the battery can take; the inverter adjusts charging and discharging.

With communication

The inverter knows what the battery asks for

Follows the current limits in real time
Shows the state-of-charge estimate reported by the BMS
Reduces charging when the battery is full or cold
Avoids protection shutdowns

Without communication

The inverter receives no data from the BMS

Uses fixed voltages set by hand
The state of charge is estimated from voltage or by an external monitor
The battery may switch off without warning
Less predictable compatibility

Simulate the BMS

Move the state of charge and the temperature of a LiFePO4 battery. The example shows, with typical rules, when charging and discharging are allowed, reduced or blocked, and the limit the BMS reports to the inverter.

What to check before buying

Compatibility list: the inverter manufacturer publishes which batteries and protocols it accepts
Protocol: CAN or RS485 is only the interface; both sides must also use the same application protocol, in the same version
Communication cable: the pinout varies; use the cable the manuals specify
Setup: choose the battery model with communication on the inverter, not the generic type
Batteries in parallel: check how the BMS units talk to each other and to the inverter

Draw it in Editor Solar

This is Editor Solar itself, already loaded with the diagram from this article. Move the equipment, edit labels, connect new parts and export to PNG, SVG or PDF. It is free and runs right in your browser.

A battery with a built-in BMS connects to the inverter in two ways: the power cables and the communication cable.

Try it: Note on the diagram the communication protocol of your inverter (CAN or RS485) and check the manufacturer’s list to see whether the battery model is compatible.

Ready-made templates: see all diagram templates

Open this diagram in the full editor ↗

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