As far as I am aware, currently Librem 5 would always negotiate 5V.
So the 9V, 12V and 15V options are never used.
The maximum that Librem 5 negotiates is 5V 3A.
Depending on the charger/hub, it could negotiate less.
You can read the negotiated value using the following command:
sudo cat /sys/class/power_supply/tps6598x-source-psy-0-003f/uevent
POWER_SUPPLY_CURRENT_MAX=500000 would mean 0,5 A
POWER_SUPPLY_VOLTAGE_MAX=5000000 would mean 5 V
I can’t tell you if it is safe to use the Dell laptop charger on the long run.
I guess that:
- It is likely safe.
- It will depend on the negotiated protocol as some protocols would produce more heat than others.
As far as I am aware, the Librem 5 is smart enough to stop the charging if it gets overheated or something. As far as I am aware this is visually shown by blinking red LED.
I use “as far as I am aware” because I might be mistaken.