Cheap Chinese fake phone chargers have been known to explode when the switch mode circuit runs away.
Thanks for the clarification! I didn't know if there were any other things I needed to be worried about. I have a few good power supplies, and for the project I'm particularly asking about, I have a 6-port 50W power supply, and I'll be using two 2A supplies for two Raspberry Pis that will be powering external USB SSDs, which need about 350mA max. So it should still be safely within the limits of what the Pi can handle with the 1.2A bus current.
I also found the following from this thread
, written by @mahjongg:
All that max_usb_current=1 does is to set GPIO38 high, which in turn turns on a FET, which connects a second 39K resistor in parallel to an existing one, on pin 5 of U13, the AP2553W6 USB power manager, lifting the current limit from 0.6A to double that (1.2A), see no possible scenario there why the PI resets because of that, except in case the gate of the FET Q4 is somehow shorted to GND. Which could be caused by a production fault. Inspect Q4, as look if there is solder shorting pins together. Also R6 (resistor mounted between gate of Q4 and GND) should be 100K not 0 Ohm. U13, Q4 and R6 should be near the USB ports.
So seems safe enough to me, as long as you are using a solid 2A+ power supply!