If your battery "dies", just push the 12 v battery reset button on the left side of the driver on the dash. It will charge the battery and you are back to normal instantly.
The 12v battery disconnects if it falls below Xvolts (I forget what that number is), the reset button doesn't charge anything, it re-connects the 12v lithium ion ferrite core battery to enable you to start the car. I've had ours stall at first start after sitting outdoors overnight in -10 below zero weather, BUT, when it stalls, at first you hear the engine shake, stutter, as is normal in such temps, the second it stalls out the Niro switches to EV mode, and in about 1 more second the car starts itself again as if you pushed the start button a second time....................this has happened twice in sub zero temps, and each time, on the 2nd firing, the car started right up. The overall design seems great..........no problems really...................I just pitty the fools that try to jump start another car with their Niro, you are NOT supposed to do that! Kia left out a warning in the owners manual stating that the Niro is NOT designed to jump start other cars and doing so can damage the vehicle, the 12v battery, and the hybrid battery,,,,,,,,,,,,,,,, you can however receive a jump start from another car/jumper battery if necessary. Kia is supposedly updating the owners manual and may release addendum's to existing customers/manuals regarding more specific battery jump do's and don'ts.