Our Hyundai Ionic, when we do a lot of highway (with no charge opportunity), will sometimes go pretty low on battery, even while its been using fuel for a good while.

Like we go down to 4%.

My SO seems to think that if we hit 0, the car will just become a brick, everything will shut down and we will be stuck.

So is is possible to hit 0% while normally driving, and if you do, what happens?

  • And what does it say in the handbook?
    – Solar Mike
    Dec 13, 2021 at 15:39
  • I read good parts of it and can't remember a part talking about that. But its been a good year so I'm probably forgetting. Should go and review.
    – Fredy31
    Dec 13, 2021 at 15:42

1 Answer 1


Every decent hybrid vehicle, no matter whether it's a plug-in hybrid or non-plug-in hybrid will work with any achievable state of charge on the high-voltage battery, with the only exception being if you store the vehicle for many months, allowing the battery to self-discharge. Electric vehicles are entirely different: they are dependent on the battery having charge.

The vehicles have the possibility to charge the battery using the internal combustion engine. They do that once the battery gets too empty. The vehicle computer never allows the battery state of charge to reach so low levels that it would brick the car.

Many hybrids actually start the engine using the high-voltage battery and not the 12-volt battery (they have a 12-volt battery too but it's used only as a buffer and power source on the low-voltage system and as a way to boot up the computers that connect the high-voltage battery using a relay). So they really are dependent on the high-voltage battery charge: if it gets completely empty, the car can't start its engine. However, the high-voltage battery never gets completely empty. If it threatens to become empty, the car will start the internal combustion engine and start charging the high-voltage battery.

So unless you are planning to drive the car until the high-voltage battery is 4% full, and then store the car unused for many months, you have nothing to worry about. (And besides, if it's a plug-in hybrid even after extended storage it may be possible to charge it back to full.) The car won't let the battery charge reach dangerously low levels. 4% of charge is plenty, plug-in-hybrids typically have 15-20 kWh batteries and non-plug-in-hybrids have only 1.5 kWh battery typically. With non-plug-in hybrids, 10% charge is plenty. This means that with plug-in hybrids, 1% is plenty. It will start the engine even at minus 30 degrees Celsius. (Also a note, if the car says the battery is 0% full, it may be calibrated to indicate it's at the lowest permitted state of charge, so 0% full may actually be something like 5% full.)

Don't let the fuel get empty, though. It's a bad idea to get out of fuel, thinking that the charge in the battery will allow the car to be driven 10 km more to reach the gas station. It may not be that way -- it may be the car will be bricked if it's empty of gas.

  • So I guess if I see my car at 4 and it seems to stay there, its because its using the currently running combustion engine to keep charge in the battery. So hitting 0 while driving is almost impossible.
    – Fredy31
    Dec 13, 2021 at 19:01

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.