Did you actually measured the current from the battery with a mA-meter?
I am working directly with the AXP192 registers, I tried something simple with UIFlow but was not to my taste...

Here is the project:
Video: https://www.youtube.com/watch?v=Goauv9xGJqY

Adrian

@easytarget The internal battery have it's own protection module; if you really want to put another one in parallel with the internal one, choose one with a similar protection module. This would be the "next best practice" if you don't want to simpl replace the internal one with a bigger external one.

Cheers,
Adrian

Finally, I solved it...
No need for 5V output on 5V_BUS because it came from magnetic base charger.
Therefore an interlock code was added:
--When 5V from battery is needed for external acc., VBUS== OFF & EXTEN==1;
--When magnetic base charger (or external 5V is applied to Socket Power (J3) on Bottom2, VBUS == INPUT & EXTEN==0.

This way, the Bottom2 LED's and othe devices are powered with 5V in any situation.

Cheers,
Adrian

Hi all, I’m investigating a power management issue on the M5Stack Core2 (AXP192 + external SY7088 boost) and I’m looking for confirmation or a proper solution.

🔧 System Architecture (as implemented)
From schematic analysis and testing:

AXP192 IPSOUT powers the system and the boost converter

// VBUS ALWAYS INPUT ENABLED  
 writeAxpReg(0x30, 0x80);

SY7088 generates 5V (when EXTEN = 1)
SY7088 output is directly connected to VBUS
VBUS is also connected back into the AXP192 as an input
ACIN is the real USB 5V input

So effectively:
BAT → IPSOUT → SY7088 → VBUS → AXP192 → IPSOUT

❗ Observed Problem
When running on battery:

-Enable 5V output (EXTEN = 1)
-Disconnect USB cable
-Immediately, battery current jumps to ~450 mA
-System enters a self-sustained power loop

🔍 Key Observations
EXTEN is correctly set (verified via register dumps, Reg 0x12 bit 6)
VBUS input is permanently enabled (Reg 0x30 = 0x80)
Boost converter behaves normally
Loop appears only when USB is disconnected

💡 Root Cause
SY7088 output is physically tied to VBUS
AXP192 does not fully isolate VBUS internally
The supposed N_VBUSEN mechanism does NOT break the electrical path

🔥 As a result:
BAT → boost → VBUS → AXP internal path → IPSOUT → boost...

This leads to:
continuous energy circulation
high battery drain (~400 mA)
no stable operating point

❓ Question to the community
Has anyone:

• Observed this behavior on Core2 or similar AXP192 designs?
• Found a way to safely use 5V boost to power external accssories from battery without loop?

Thank you,
Cheers,
Adrian YO3HJV

Hello,
This is my first post here and also my first project with M5Stack devboard.

It is a standalone and simple music player as a first step to a more complex one.
I named it "RunMan" because, you know, the "Walk" one is a trade mark :-).
It is available on M5Burner and also on my GitHub.
Please feel free to test and criticise; this way RunMan II (in development) will be better.

Cheers,
Adrian