Hi @david,
the reboot or freeze was caused by the memory leak bug which is solved since 1.3.1-rc.1. This bug caused the free heap to be reduced by ~5kb every modem restart. So a reboot or freeze occurred after some modem restarts. The modem restarts had been caused by the power issue. So the power issue was only an indirect cause for the reboot/freeze!
If you are using 1.3.1-rc.1, your reboots or freezes have another cause as the memory leak is fixed. If not, please update 
Check also if your power supply can handle the current and if the voltage is stable in case of current spikes.
This is my code:
PMIC pmic;
pmic.begin();
pmic.setInputCurrentLimit(3000);
pmic.disableCharging();
pmic.disableBATFET();
byte DATA = pmic.readChargeTermRegister();
DATA &= 0b11000110;
Wire1.beginTransmission(PMIC_ADDRESS);
Wire1.write(CHARGE_TIMER_CONTROL_REGISTER);
Wire1.write(DATA);
Wire1.endTransmission(true);
- Increase input current limit
- Disable charging and disable batfet to tell the PMIC that there is no battery
- Disable safety timer to disable charging led blink after some time (optional, source: Disabling the Electron red charging LED when not using the LiPo)