Another option is to use a dedicated USB--> li-ion charger, they are commonly available for charging cheap vape-cigarettes, I see them for about 1-5 euros. Easy to crack open and connect the correct polarities, it charges enough to boot in a few minutes or safely use it to fully charge your battery should the charging system be damaged or inoperable.
If you are in a dire situation where you NEED to get a booted phone you can cut any USB cable and connect the correct polarity to the poles of a li-ion battery for a minute or so and have enough to boot if not another 60 sec until you can get normal internal charging. 5v is just outside the spec but I have never had it be a problem as 5v should be within the engineering reserve for a standard Li-ion battery <<<but can overcharge and damage the battery>>> if used to do a real full charge and not just get the V high enough to boot the bootloader and enable the phone's internal charger.
None of this is specific to Pinephone but is general for nearly all ~3.6v Li-ion batteries and devices which require sufficient voltage in the battery to get start up a bootloader to get charging started.
Again the emergency hack uding a stripped USB cable is bad practice but should get you back to charging voltage in nearly all cases without damage though some batteries and devices are non-standard conforming so do at your own risk in an emergency when you REALLY NEED to get communications restored and need to take a small risk.
If you are in a dire situation where you NEED to get a booted phone you can cut any USB cable and connect the correct polarity to the poles of a li-ion battery for a minute or so and have enough to boot if not another 60 sec until you can get normal internal charging. 5v is just outside the spec but I have never had it be a problem as 5v should be within the engineering reserve for a standard Li-ion battery <<<but can overcharge and damage the battery>>> if used to do a real full charge and not just get the V high enough to boot the bootloader and enable the phone's internal charger.
None of this is specific to Pinephone but is general for nearly all ~3.6v Li-ion batteries and devices which require sufficient voltage in the battery to get start up a bootloader to get charging started.
Again the emergency hack uding a stripped USB cable is bad practice but should get you back to charging voltage in nearly all cases without damage though some batteries and devices are non-standard conforming so do at your own risk in an emergency when you REALLY NEED to get communications restored and need to take a small risk.