Miracle car drives after it runs out of gas...or does it?

December 22, 2005 12:30 PM

What happens when a Hybrid car (i.e. Prius) runs out of gas? Can it keep driving on the battery?

I see here that "The Asian and European versions of this vehicle provide a button labelled "EV" that maintains electric vehicle mode after startup, under most low-load driving conditions." But I'm in the US and I'm just windering how far I could drive after the tank runs dry.

posted by clgregor to travel & transportation (10 comments total)

...And is there a hack for the US version?
posted by rxrfrx at 12:37 PM on December 22, 2005

I don't know about that, but I have heard that if you car battery (Not Drive Battery) dies, you cannot start the car as the gas engine runs off of a separate 12v battery just like a normal car.
posted by stew560 at 12:50 PM on December 22, 2005

I have friends with a Prius. They were able to drive a short distance (say, under 10 miles) on just the electric engine after running out of gas with complete confidence.
posted by anastasiav at 12:54 PM on December 22, 2005

I own a 2004 Prius (the hatchback model) and before that owned a 2002 Prius (the sedan model). You can drive a short way on battery power when you run out of gas, maybe enough to get safely to the side of the road, perhaps enough to reach a nearby gas station. Supposedly, Bad Things Will Happen if you run out of gas and try to drive too far on electric power only. There are instructions/kits on several Prius owners groups for adding the EV button and electric-only capability to a US Prius, but it voids the warranty and I'm too chicken to try it. Prius enthusiasts were hoping for EV capability in the new model year, but I don't believe that the 2006 Prius has it. The Prius has a small 12v battery that boots up its computers. (It doesn't have an actual starter.) If that battery dies, you can jump it just like any other car battery. You don't mess with the high-voltage batteries. It's a wonderful car, and I would never ever go back to driving a "regular" car.
posted by Joleta at 12:59 PM on December 22, 2005

This has been discussed extensively on various Prius email lists.

Yes, the car will keep operating, and you can drive slowly and with slow acceleration on battery power alone. This will not get you much further than a couple of miles or so (gasoline stores LOTS of energy compared to batteries, even large batteries like the Prius'). The gas engine always tries to come on at speeds over 42 mph, so I wouldn't know (or want to find out) what happens if you try to push a Prius with no gas faster than 42mph.

It is somewhat dangerous, as if the Prius' main battery is discharged too far, it can be damaged. So you would have to keep a close eye on the battery gauge and drive quite cautiously.

So: if you can see the gas station, sure, you can nurse the car there. Otherwise, call AAA.

If you Google for prius ev button hack, you'll find a PDF detailing how to perform the procedure.
posted by jellicle at 1:01 PM on December 22, 2005

Anecdotally, yes, you can go a mile or two, as the batteries do not hold a massive charge. Toyota warns against doing so, and the general consensus is that it is very bad for the batteries.

I am told that the car will not start when it is out of gas. (I'm waiting for mine to arrive, but don't plan on running out of gas to experiement.)

I'm not completely familiar with the intricacies of the EV hack, but I would think your speed and distance would be badly hampered without the gas assist. You can read more about it on any of the Prius message boards, though.
posted by Lyn Never at 1:02 PM on December 22, 2005

You can buy kits to refit a Prius with a charging plug, so i know that the capability to run American versions as pure electrics does exist. Toyota America has nixed the charging plug and other evidences of it on American versions because they felt that there was great marketing value in being able to say "See? No plug!" Oddly, they didn't seem to have confidence in their sales network's ability to just ignore the thing.
posted by lodurr at 1:02 PM on December 22, 2005

My understanding is that some of the hardcore people who do the EV hack with the intention of driving in EV mode a lot also add additional batteries, since the existing one is tiny compared to those in EV-only cars, because was not designed with enabling EV use in mind, just much better mileage (hence the need for a hack to implement it).

I Am Not An Expert though. I didn't even know that some Euro models could come with an EV option factory, that's very cool.
posted by -harlequin- at 1:09 PM on December 22, 2005

Well, the EV button exists overseas. So the EV button hack just replicates something that Toyota has in production and can be deemed "safe". The button makes a suggestion, which the car can override, that the car stay in electric mode as long as possible.

The same people have also made extensive modifications to the Prius including larger battery packs and the ability to recharge the main battery from your home AC. These are absolutely not Toyota-approved modifications...
posted by jellicle at 1:15 PM on December 22, 2005

It happened to my dad on the freeway...
he was able to go a couple miles and was fortunate enough to coast down an offramp, hit the green light and coast into a gas station.
posted by clh at 1:30 PM on December 22, 2005