M5 CoreS3 power drain issue.

lweiyen

My M5 CoreS3 develops an issue that the battery drains within half an hour from full and it heats up a lot. I has been programming with it together with a gps module and then a gps unit with no issue for about two weeks. I revert to demo program and disconnect all peripherals and the issue persists. I use the power options in the demo program and find that with bus out on the unit heat up to 60 degree and with bus out off the unit cool down to 40 degree. Any suggestion how I can troubleshoot this further?

lweiyen

Please see the demo program images to better illustrate what I observe. This is just the core s3 with demo program without anything else attached/connected.

felmue

Hello @lweiyen

from a fully charged battery my M5CoreS3 was running about 3.5 hours until shutdown. Bus out was on, nothing connected to it and the temperature was about 30 degrees.

I noticed that your bus voltage reading is 5.0 V (mine shows 5.1 V). It is almost like there is some load?

I can force mine to go down to 5.0 V by adding an external load of about 15 Ohm. Then I see the temperature rising, but still only to about 42 degrees.

Given that your M5CoreS3 heats up to 59 degrees suggests there is an even greater load / internal short.

Given the battery is 500 mA/h and yours is drained after half an hour would suggest a current of about 1 A out of the battery.

Thanks
Felix

lweiyen

@felmue
I have opened up my unit further and, with some thermal probing, found that the highlighted chip gets to 70 degree and seems to be where the short is. I know that my unit is pretty much dead with this short. I just wonder if anyone know what this SJVL chip is as google failed to gives me any hint.

felmue

Hello @lweiyen

if I am not totally mistaken this is U17 - it's used to power USB (OUT) when running from battery (and BUS is set to OUT).

Please see my drawing here and schematic here.

Thanks
Felix

lweiyen

I recall the last action before I started to have the issue and I now suspect it was my particular scenario of charging the din base battery that might have damaged one or more of the power distribution mosfets. I shall describe the scenario here as a caution for fellow core s3 owners.

firmware installed: uiflow 2.0.1
external device connected: M5Stack GPS/BDS unit connected to port c at the din base.
charger used: wall charger with multiple usb c and a ports. one of the usb c port was used.
sequence of event:

a gps related uiflow program was running and the battery dropped low
connected the wall charger to the core s3 with a usb c to c cable to charge the battery inside the din base
after some time switched off the core s3 by holding the power button while the charging is still going on
core s3 felt very warm to the touch but I did not think too much of it.
charging was completed after the red indicator turned off

I suspected that in sequence 4 one or more mosfets were overheated and damaged.