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A thought struck me today for some odd reason. I've always been "afraid" that what if the internal combustion engine (ICE) wouldn't start up when I needed it. In an attempt to figure out a scenario where it wouldn't, this popped in my head.

Let's say I've travelled up to the top of the highest peak, and have totally drained the battery that drives the electric motor. If I understand the car correctly, the ICE gets started by the electric motor, which gets its power from the "big" battery. The small battery in the hatchback is strictly for running the 12V accessories (including the A/C?), and is not used to start the ICE. (Right?)

So if at the top of this hill I have to stop at a stoplight, will the ICE stop like it always does, or will it take the opportunity to charge the battery?

If I stop at the top of the peak to get out and take pictures and turn off the car, will the engine be able to start back up, and how? I assuming that the car will turn off the ICE when I press "Power," or will it be smart enough to say, "Heck no, buddy! I gotta charge the battery a bit. I'll turn off after that."

As I'm driving up the hill, will there always be guaranteed a certain amount of ICE driving the generator to keep enough of a charge to start the ICE up if it stops?

Any of you super technical Prius folk have an answer? I'm just looking for that one instant where I would push on the pedal and the car would just laugh at me... (Not that I want it to happen, but I want to prevent it from happening.)

thanks in advance!
 

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The car will not drain the battery completely

I have been wondering if the A/C is high voltage or low voltage myself
I would assume high voltage

some facts ( as I understand them :shock: )

Big battery charges the small battery

Battery gage you see is only showing you 40% to 80% charge
for example if the last battery bar just disappeared you would still have 40% battery
 

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You're Prius will try really, really hard not to strand you with a dead HV battery. None of the scenarios you mention will trouble it. As artman67 mentioned, when you think you've drained it (gauge goes to no bars, battery won't provide any assistance), it's still got 40% of it's charge. This is enough to start the engine a large number of times. Whenever it's below 55% charge, the computers start actively looking for ways to run the engine at a higher load to get the battery charged. Below 40% (probably a higher number) it won't shut off the engine when you stop (unless you turn the car off).

If it's not Ready, it won't use the HV battery to charge the 12 V or to run the AC, so it doesn't have to worry about running out the charge when it's not allowed to start the engine.

If you run out of gas, it will run electric to a lower point than the usual 40% barrier (or so I've heard). But it will still retain enough charge to restart the engine two or three times after you fill up.

Keep in mind that it takes WAY less charge to start the engine than to move the car.
 

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Today I needed to get in front of someone at a stop light, right after it turned green I punched it and the ICE came on, then cut out, right away, but then came back on. Is this a problem?
 

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ephrumsirc said:
A thought struck me today for some odd reason. I've always been "afraid" that what if the internal combustion engine (ICE) wouldn't start up when I needed it. In an attempt to figure out a scenario where it wouldn't, this popped in my head.

Let's say I've travelled up to the top of the highest peak, and have totally drained the battery that drives the electric motor. If I understand the car correctly, the ICE gets started by the electric motor, which gets its power from the "big" battery. The small battery in the hatchback is strictly for running the 12V accessories (including the A/C?), and is not used to start the ICE. (Right?)
Right, but it can also use excess power in the system to start MG1 which starts the ICE.

ephrumsirc said:
So if at the top of this hill I have to stop at a stoplight, will the ICE stop like it always does, or will it take the opportunity to charge the battery?
Depends on how flat the main batttery is. If its at or neat 40% then the ICE stays on, otherwise it switches off.

ephrumsirc said:
If I stop at the top of the peak to get out and take pictures and turn off the car, will the engine be able to start back up, and how?
Yes, like normal.

ephrumsirc said:
I assuming that the car will turn off the ICE when I press "Power," or will it be smart enough to say, "Heck no, buddy! I gotta charge the battery a bit. I'll turn off after that."
No, it will turn off.

ephrumsirc said:
As I'm driving up the hill, will there always be guaranteed a certain amount of ICE driving the generator to keep enough of a charge to start the ICE up if it stops?
As above. If the power falls to low, then the ICE will kick in. However, you may well find that the ICE is running all the time on a hill. When you get to the top, you can move the selector to B and use engine breaking to help top up the power oi its really low, but dont forget to go back to D asap.

ephrumsirc said:
Any of you super technical Prius folk have an answer? I'm just looking for that one instant where I would push on the pedal and the car would just laugh at me... (Not that I want it to happen, but I want to prevent it from happening.)
Leave the car with the stereo on for 3 or 4 weeks and go on holiday. When you get back the 12v will be flat and you wont be able to start :wink:

Look at http://www.prius-forum.org > Technical > Prius introduction for how the system works.

ephrumsirc said:
thanks in advance!
The system always keeps the main battery charcged between 40 and 80%. Dont worry about it, just drive it.
 

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Victor said:
Leave the car with the stereo on for 3 or 4 weeks and go on holiday. When you get back the 12v will be flat and you wont be able to start :wink:
It takes a lot less time than that. Do not let your daughter sit in the Prius in Accessory (i.e. not Ready) mode listening to a CD for an hour (with the door open so the dome light is on) while you chat with other Prius afficianados. You'll have an embarrassing failure to start moment!

I speak from personal experience :oops:

Happy ending though... Since it was a warm day and the 12V battery had just been drained, I let it sit for 5 minutes with everything off and the battery recovered enough to boot the computers so they would throw the relay to let the HV battery take over. Then everything started just fine.
 
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