@jimit 在 Battery issue 中说：

believe the connector on that is a JST SH with 1.0 pin

Can somebody confirm 100% sure the connector format ?

@world101 在 Review "BATTERY" 中说：

@donck
Thanks. What core module version(s) do you have?

The grey limited edition and the one with PSRAM (both performing the same)

@world101 Using the 150ma one, I can run my M5Stack limited edition for 30~40 mins with the screen turned off and a simple program running, doing nothing else than turning the screen off (WiFi was not setup).
Running in the same conditions, I think the 850 should run for ~3 hours approximately.
I ordered one but I cannot confirm yet.

The positive pin is on the side of the 2x15 connector, the negative one is on the side of the SD slot.
I also presumed the size is JST SH and order a battery, but I cannot confirm yet.

@kaotiklabs Try to connect the device to the charger and then put the device to sleep mode (the SimpleApplicationMenu example can do that) and wait for one hour. Did it improve the charging ?

A bit off-topic:
Can someone using a battery gauge indicate how long does the 150mah battery takes to charge on an M5Stack limited edition ? (assuming ESP is sleeping)

(FYI, with the screen backlight turned off, and not connected to any network, the battery lasted for 40 minutes with the ESP not sleeping)

Audio amplifier auto off

I suggest to hardware implement auto-disabling of the audio amplifier when not playing any audio.
Some power savings could be achieved and the device would be prevented from producing unexpected noises.

How:
The audio amplifier chip has an "enable" pin.
I think it would be a good idea to use a low pass filter fed from the audio output so it would disable the amplifier after the "dac" was set to 0 for long enough.
This way, it would not be necessary to allocate one of the ESP32 outputs to control the amplifier chip.

Another one wich looks even more promising :
https://github.com/earlephilhower/ESP8266Audio

MP3 doesnt seem supported by the M5Stack library, however the Speaker class has 8bit PCM support:
void playMusic(const uint8_t* music_data, uint16_t sample_rate);

Still you would have to bind it to the SDcard files, by now the audio is defined in startup_music.c as: const unsigned char m5stack_startup_music[]

Also, this could help you:
https://github.com/MrBuddyCasino/ESP32_MP3_Decoder

Just to be clear, to me there are two types of noises:

Light white noise : I believe this one is probably due to the quality of the audio amplifier.

A higher pitched noise, much more annoying.

On my device (M5Stack limited edition), only the 2nd one is affected by the display setting.

For that second one, not everybody may be able to hear it, depending on multiple factor including aging (presbycusis).

Update: I received my M5Stack with PSRAM, it behaves exactly the same.