MUDI Battery Charging

I’m an electrical engineer, so I’ve got a bit of background in this area, but obviously I don’t know what charging solution is being used in the MUDI.

Is there any way to disable the charging circuitry via software? It seems like there are a lot of power management ICs nowadays that have an input pin to enable/disable the charging functions and allow external power only. Does the MUDI have this capability?

It would be very nice to be able to manually disable the charger to allow it to be plugged in indefinitely. The warning on the box to not leave it charging unattended worries me a bit, but for a modern device, this should be easily managed.

The warning is fairly standard, and comes with any and all battery operated devices. It’s just the manufacturer covering their bases, because while the hardware should be safe for continuous charging, the IC might get damaged by a surge and cause a fire, in which case GL.inet can just say “sorry man, we told you not to leave it on the charger”.

Precisely. The charging IC should be protection enough in the Mudi, and Li-Ion batteries today are not as fragile as they were ~10 years ago. The chances of a fire are low, but not non-existent.

In fact, the charging IC should work in a way that while charging, the battery acts as a backup/UPS unit.

In fact, if it’s possible to turn the charging function on and off, I’d love to have that tied to the switch on the Mudi - it would make a lot of sense, you pick it up, and with a click enable charging the battery, or disable it.

Mudi has an all in one charger + voltage regulator + monitor, don’t remember if you can just disable charging.

If i remember correctly, while Mudi is plugged in, the battery is constantly being topped off, trickle charged, which is not the best for the LiPo’s, that is why it’s not recommended to keep it plugged in.

To me that looks like a programmable PMIC. The placement is also a bit funky - isn’t it usually recommended to have the PMIC close to both the battery port and the power input port?

Also, my eyes spy two little hidden buttons on both sides of the SD card reader. What is the function of those?

And last note - I love the fact that you’ve made the 5GHz WiFi modular - meaning that it should be relatively straightforward to add a WiFi 6 radio in this shape and form once Qualcomm releases one, right?

I’d like to make it clear that I’m not worried about the battery catching fire. I’m more concerned with the battery prematurely failing if I were to leave it plugged in 24/7.

I’d hate to pick it up one day and find the case bulging out from a swollen battery.

I was just thinking that maybe the charge enable pin on the PMIC was tied to a GPIO pin that could be tied to the side switch or a button in the GUI.

One is the reset button, but there is an unmarked hole probably for the second one. I’m gonna push it…

@luochongjun Is there a way to disable the battery charging via pin?

@Johnex could you give us some details regarding what kind of PMIC is being used in the Mudi? That might be a bit more helpful for customised control (I have a gut feeling it communicates with the SoC over I2C, but without the precise manufacturer and model number, I can’t say for sure).

It should not happen - modern PMIC charge to ~80% capacity, then trickle charge until fully charged, and the unit should be running entirely from the external power source. Once the battery charge drops below 80% again (which, given it’s not being used, should not happen for weeks!), it will trickle charge again till fully charged, and repeat this process. Older PMIC, however, supplied continuous charge to the battery to keep it topped out, which was the source of explosions (PMIC receiving sudden jolt of power, providing overvoltage to an already topped out battery, which on the long run degrades the chemical reaction and leads to a thermal runaway).

Unless you somehow manage to discharge the battery while charging (i.e. making the unit use more power than what the external power supply can provide) multiple times, it’s doubtful that it would happen. Also, given the above internal view, the Li-Po cell should be straightforward to replace (it’s a dual parallel cell LiPo with the standard 5 pin connector), as long as you can find a fitting size.

Most likely not GPIO, but I2C - the PMIC already communicates a lot of data towards the SoC (battery status - voltage, degradation, discharge/charge status, and so on, external power status and voltage/amperage, et cetera) so that it can display that to the user. This communication might even happen through a serial port, but most definitely not just over a simple GPIO pin.

What happened after you pushed the other button? I presume it did not cause any nuclear explosions, and your cat is alive as well (if you have one), so it must be relatively harmless.

I’m tempted to open mine up and see which PMIC is used and check out the datasheet.

Yes, there’s probably a lot of I2C traffic going back and forth, but there’s almost certainly an enable pin on the PMIC that might be used. I don’t know if toggling that input would just turn the PMIC off completely and kill all power, though.

The “hidden” button in the unmarked hole to the right of the SD slot is a system reset button. Pressing it turns the MUDI off, and upon release, it powers back up to the shutdown state, with the battery level displayed on the screen when you push the side button.

I agree that the battery should be easy to replace, but I’ve had devices physically damaged by swollen batteries, especially in a sealed box like this. The swelling could break the screw mounts near the SIM and SD card slots. I’m not sure how important this screws are,

Edit: looking at the picture again, it looks like those screws are required to help press the SIM card against the board.

There is no way to completely ban battery charging. There is a power control IC on the E750, which will automatically control the charging status of the battery to ensure the battery safety.