rear hatch will not open...dead battery

you can put a 12v source on the jump point under the hood in the fuse box (see owners manual)

or you can crawl into the hatch and use the interior emergency opener (see the owners manual)

take a flash lite and small screwdriver to pop the cover

amazing anything is happening at 6 volts

 

let us know how you make out. i had the same thing last summer, but 4.5 volts

 

I had pretty much the same thing a couple weeks ago, although I still don't know what killed the battery, which had me freaked out for awhile fearing a repeat at an inopportune time. I put 12v "jumper box" on the jump point under the hood and even that wasn't enough to get the hatch to open. After trickle charging overnight (and then some), everything came back online and no further issues (knock on wood).

At the time, I lined up Plan B, which was to use the interior emergency opener and found/saved this video which demonstrates:

 

Are you charging the battery? Are you saying you have it on a charger but won't go above 6volts?
Is your charger set to 12volts?
Leaving the headlamps on, no matter how long, will charge the battery.
All the lights are flashing because they are trying to light, but not enough power.

It confusing on what you are writing.

Putting a charger at the fuze box should be enough to allow you to open the hatch.
You may have to let it sit for a while to charge up the battery...

 

How timely this post was for me. I purchased my 2012 Prius4 last month. This morning the battery was dead after my wife left the lights on, thinking that they would shut off automagically. You folks just answered all my questions. Thanks!

 

I've left the lights on a few times. Pretty stupid of me, but I'm antique.
They turn off for me. I'm not sure how long they stay on before shutting off.
I just remember turning it on in the morning while it was still dark and the lights came on.
I'm certain 8 hours with the lights on would kill the battery.
Maybe someone turned that feature on your Prius?

 

may depend on the level or year. they packed a lot of goodies in the 10's, in an effort to sell them, then slowly decontented

 

Leaving the headlights on is fine, they automagically turn off in [ 0 | 30 | 60 | 90 ] seconds, customizable. Beware that there are a couple ways to accidentally defeat this automagic shutoff, but if the battery still had 6V after more than one day, then this error didn't happen.

If the car was unused for months, and the battery was still the factory unit, then I believe it just reached its natural end of life. At 6 to 7 years old, this is normal, even better than average. You could have eeked out more life by running the car much more frequently, or by using a battery tender while the car was in hibernation, but even with those measures it would still be very close to its end of life.

Exterior lights do turn off automagically in no more than 90 seconds, unless the sequence is defeated (by touching the light switch after ignition is turned off, or by exiting through something other than the driver's door). Some interior lights eventually go out automagically, some others may not. As with the OP, if the 12V battery is original, it is beyond its typical life expectancy and has little capacity or margin left. And with cooling temperatures as winter arrives, this is the season when many people discover it.

 

This is the third post this week about the wife doing something fatal to a Prius.

 

Turned she had turned everything off then realized she couldn't see. So she turned the lights back so she could walk in from garage. I tried charging with no luck. New battery took care of the issue. The irony is that dead battery was installed in August.

SM-T720 ?

 

Yup, if done after ignition shutoff, that defeats the automagic headlight shutoff.

Summary: if you don't touch the exterior light switch at all during or after car powerdown, the car takes ownership of the lights-off process, turning them off automagically. But the moment you move the light switch, you own the shutoff responsibility. The car treats your action as an intentional override.

Remember also that car's automagic countdown timer is started by opening (or closing?) the driver door. If you exit instead by passenger door, window, or sunroof, or simply stay (sleep) in the car, be ready for a dead battery.

Beware that interior lights are treated differently. Rather than remembering which are and are not eventually turned off, I replaced them all with low current LEDs so the battery will survive to the next day. This also will help if stranded and needing to spend an extended period in the car. As a traveler to and through remote places, without cell coverage, this is always a possibility.