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Shutdown From Quick Change in 12v input voltage

Separate post as different question area.

 

My rpi2 with Amp+ system is powered by a 12v AGM battery that is recharged by a  battery maintainer that is always attached to the battery.  The system just stopped all by itself once and I have been trying to find out why.

 

My current hypothesis is that a quick ~0.5 volt drop in the input p/s voltage when the maintainer stops charging, even though input voltage is regulated by the amp+. This is because a slight change in the GPIO pin voltages and the shutdown script senses this, just like a pin short, and shuts the system down.

 

The system is in a headless stage so I do not readily have console output access so this is a hypothesis.  I can reproduce the auto shutdown by running battery down so the maintainer turns on then just turning off the AC power to the maintainer giving ~500mvolt drop in input voltage and it appears the rpi2 does a safe shutdown, as if the shutdown button was depressed.

 

Does this make sense from a hw perspective? If this is true this would be a common issue for any significant fluctuation in input power to the rpi (thru amp+ or regular 5v micro USB port) with a proper shutdown method based on GPIO signals?

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