Left the headlights on...car won't turn

You won't do any more damage, but a simple jump start may not work if your battery is too far gone.

Guess it also somewhat depends on what the health of the 12v battery was before the incident.

FYI the 12v battery is in the trunk area.
But there is a jump start terminal under the hood.

 

Ideally you would boost the car and get it started tonight. But that is hardly practical for you as a new owner to do in the dark at your cold temperatures. If you were a AAA member it might be worth a call to see if they would come out. If not I would leave it to do in the morning. Use this evening to do a search here on boosting the Prius and how to do it. It is different than other cars and if it is not done correctly can do a lot of damage. Any more questions and come back here to get answers, there are lots of people here who can help.

 

I would get it on a smart charger, 4 amp range. It'll likely take up to 12 hours, considering the depleted state.

Assuming you're able to restore it, start monitoring, at least the voltage, with a digital multimeter, with the car off. If it will stay above 12.6 it'll be ok for a while. Testing it with Solar BA5 or similar will give you a better idea of what to expect, if it's worth sticking with it or replacing.

 

welcome!
same thing happened to my daughter two nights ago in our driveway. i was able to charge it overnight, and drive it to the local mechanic to have a new battery installed. if yours is original, you should buy a new one.
if you don't have a charger to get it going, be careful jump starting. cross polarizing the leads can do serious harm.
all the best!

 

in that case, you need to charge or jump it. but even a new battery drained in this weather may be toast.
if you can't get it going, there is a warranty.

 

Do you have the owners manual for the Prius?

It describes the process there.

 

brutal cold. very hard on batteries, especially when drained. i think the new toyota 12v gets a 2 year unconditional warranty, then prorated.

 

yes, the sooner the better. but if it's too cold, and you don't feel like it, i don't blame you. worst that happens is you get a new one free.

 

i would do the same. wait until tomorrow, cooler heads prevail. worst that happens is you take the battery back for a new one. not fun i know, especially on a holiday weekend.
maybe it will fire right up, and not be a problem.

 

not sure what you mean, what else besides the battery?