ATTO 3 Battery SOC Discharge Behavior Issue

[YAQ0T]

ATTO 3 Battery SOC Issue Report

Overview

This document describes an issue encountered with the ATTO 3 battery and inverter system, where the State of Charge (SOC) does not behave as expected during discharging.

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Expected Behavior

When the ATTO 3 battery is fully charged:

• The inverter should display a 100% SOC.
• As the battery is discharged, the SOC should gradually decrease until it reaches the programmed cutoff point.

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Actual Behavior

The SOC behavior is inconsistent and displays abrupt drops:

• After a full charge, the SOC drops directly from 100% to 70% and then to 50%, while the voltage remains above 420V.
• As the voltage decreases to 418–419V, the SOC suddenly drops further to 19%.
• The SOC reaches 0% when the voltage falls to approximately 405V.

Voltage Configuration

• Maximum voltage: 430V
• Minimum voltage: 370V

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Steps to Reproduce

1. Charge the ATTO 3 battery to full (430V).
2. Start using the inverter and monitor the SOC behavior as the battery discharges.
3. Observe the SOC readings and corresponding voltage levels throughout the process.

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Settings

Parameter	Value
Software version	7.9.2
Battery used	ATTO 3
Inverter communication protocol	CAN
Hardware used for Battery-Emulator	LILYGO
CONTACTOR_CONTROL	yes/no
CAN_ADDON	yes/no
WEBSERVER	yes/no
MQTT	yes/no

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Additional Information

Below are some images illustrating the observed behavior:

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[YAQ0T]

Hi guys any updates ?

[dalathegreat]

Really not possible to make the estimated SOC% based on voltage better. The LFP has such a flat charging curve, so any load from the inverter will significantly impact the reading.

We will try to add crash-unlocking to the software as soon as someone can provide log files: https://github.com/dalathegreat/Battery-Emulator/wiki/Battery:-BYD-Atto-3#how-do-i-unlock-a-crashed-battery