Standalone boot-up with 1-cell LiPo battery

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Masatsune Tokuhira

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Feb 2, 2019, 9:18:37 AM2/2/19
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Hi,


Here are two charged LiPo batteries. When connecting 860 mAh, the PocketBeagle can start normally. If it is 280 mAh, press POWER_MINI_PUSHBUTTON and power down after 4 user LEDs light up in around 5 seconds. Even with a 280 mAh battery, once it is started with the help of the power supply from the USB, it can operate only with the battery after that.


Does it stop because it is not able to supply enough current at startup? I do not have an ammeter, but I'd appreciate it if you know someone who knows how to check it.


Does anyone have an example that standalone operation is possible with a small battery? If there is any contrivance in the electric circuit and/or boot sequence there, I would like you to share it.


pocket_battery.jpg

Dan Julio

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Feb 2, 2019, 11:55:29 AM2/2/19
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IIRC, the pocketbeagle can see current spikes over 200 mA from the battery while it is booting, although it takes less power after it is booted and idling.  Probably one of two things is happening.  The battery voltage droops and either its own protection circuitry cuts off the power or the PMIC on the pocketbeagle shuts down the system.

You might be able to see it happening with a voltmeter if you have one monitoring the battery voltage while you try to boot.  The voltage will suddenly drop if the battery circuitry is cutting out.  Or it will recover some after the pocketbeagle shuts off if its PMIC is cutting out.

Make sure, if you're going to try to power the pocketbeagle with a small capacity battery, that it is capable of greater than 1C discharge.  Even then it won't last long depending on what you are doing.  

Masatsune Tokuhira

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Feb 3, 2019, 10:19:26 AM2/3/19
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Thank you for the helpful information. That make me clear.

Spike of 200 mA and 1C output are not so difficult to endure, so I felt hope and worked. And I certainly observed that the voltage drop is occurring. I thought that both batteries were almost fully charged, but I understood that 280 mAh was exhausted. I misunderstood that the battery is being charged with USB connection, but I learned today that it will not be charged under the default condition.

If it was charged properly even with a 280 mAh battery it could be launched as standalone. My current project structure is only one ADXL 337 hanging. If it is in the range where the function can be achieved, I would like to challenge the clock down.

After reading the datasheet of the PMIC, I would like to add a resistor to charge it and add a capacitor as needed.

2019年2月3日日曜日 1時55分29秒 UTC+9 Dan Julio:

Dan Julio

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Feb 3, 2019, 11:16:30 AM2/3/19
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I'm not sure what resister you are thinking of adding but remember that the kernel fully shuts down the PMIC during power-off and that includes the ability for it to charge the battery.  You can reconfigure the PMIC after boot to allow charging after shutdown but there are other issues.  See this thread

https://groups.google.com/forum/#!category-topic/beagleboard/pocketbeagle/fm3O6nm06c8

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