Latitude 5400 EC firmware charging issue with OEM 68Wh battery

Hello all,

I have a Dell Latitude 5400 laptop and a reproducible battery-charging issue that appears to involve Embedded Controller (EC) charge-init logic.

Summary of issue
With a genuine Dell OEM 68 Wh battery I installed after replacing the original dying 42 Wh (3-cell) lithium-ion battery that came with the device, the system will not initiate battery charging while the system is running (ACPI S0).

Charging only begins if AC power is connected while the system is fully shut down (ACPI S5). If charging is initiated in S5, it continues normally after booting into Windows and charges while in Windows normally. If AC is connected after the system has already booted, the battery remains idle and does not charge but it will hold the current charge level (whatever percentage that happens to be).

Environment

• Model: Dell Latitude 5400

• BIOS: 1.43.1 (issue also reproduced on other Latitude 5400 units running earlier BIOS versions)

• OS: Windows 11 Pro

• Battery: Internal Dell Original Battery 4GVMP 7.6V 4-Cell 68Wh for Dell Latitude 5400 5500 / Precision 3540[E100] 

• AC adapters tested: Dell 65 W, 130 W, and 180 W (all correctly detected in BIOS)

Scope

• This behavior has been reproduced using the same 62Wh OEM battery across three separate Latitude 5400 systems.

• All systems show identical behavior.

• This probably suggests an EC firmware / battery compatibility issue rather than a single-unit hardware fault or OS issue?

Observed behavior

• AC connected after boot → battery does not begin charging (idle state)

• AC connected while system is powered off → battery begins charging normally

• Charging continues after boot if initiated while off

• No battery, adapter, or power errors reported in BIOS, Dell diagnostics, or Windows

• BIOS power event logs show normal ACPI transitions only

Troubleshooting already performed

• Verified genuine Dell OEM battery

• Tested multiple Dell AC adapters

• Verified correct adapter wattage detection in BIOS

• Performed EC power drain / reset

• Disabled all battery management features (Adaptive Charge, Peak Shift, etc.)

• Reviewed BIOS and Windows logs (no relevant charging errors)

Assessment
This appears to be an EC firmware charge-init compatibility issue affecting runtime charging (S0), while offline charging (S5) functions correctly.

What im hoping to gain from this

1. Confirmation of any known EC / battery firmware compatibility issues for Latitude 5400

2. Guidance on BIOS or EC firmware versions compatible with this OEM 68 Wh battery

3. Availability of an updated or corrected BIOS / EC firmware, or downgrade guidance for validation

At this point Ive exhausted my own troubleshooting abilities and would be great to know if someone has already had this same or similar problem and how it was resolved.

Thank you!