Battery dead (?) and Prius stuck in ACC mode (maybe?)

My 2004 Prius has been experiencing 12v battery drains (usually totally understandable ones, from dome light left on, door ajar, etc.) off and on since I got it (used, this time last year). Last week, I drove it to my son's preschool and after class was done two hours later, the car wouldn't start even though no doors were ajar or lights were on. I had left the headlights turned on (which, they normally power down after the car is shut off, but maybe that was too much for it?) I turned those off and within 20 minutes, I tried it again and she fired up and on with no problems (except the usual message about the parking being abnormal).

Last night - same situation, only it can't be restarted in the same quick-fix, self-healing way. (It's much colder here now, if that's a thing.) This morning, I tried to go into ACC mode to run the 12v battery test, but there wasn't even enough power to light the nav screen. Tried jumping off the battery with a neighbor's gigantic truck - nothing. (This has worked in the past, but not this time.) Now, the car seems to be stuck on in ACC mode but with only the orange "check engine" light illuminated. Is it even possible for the Prius to be trapped in ACC limbo? I can't power it down to get the CE light off.

I'm assuming the 12v is damaged/dead (not sure if it is an original or not - I know I should just go look, but I don't know exactly what I'm looking for to tell whether it's manufacturer or aftermarket battery, and it's so cold out that I don't even want to go back out there). Will it being "stuck" in ACC mode (presumably?) hurt the Big Cahuna hybrid battery or the rest of the car - is that even a possibility, or am I overthinking this? Do I need to disconnect things to get it powered down?

Thanks in advance, and apologies if this issue has been addressed elsewhere - I searched and found lots of helpful threads, but if there's one with this same exact scenario I must have missed it.

TIA!

 

Hmm, I hope you're right about that first!

I didn't know it was going bad until I suspected as much last week ... when a battery dies after the door sits ajar all night, that seems more like a reasonable cause of perfectly understandable drain than a huge red light saying, "Oh, obviously this battery is kaput." Not that I really would have had the money to spend on the battery just on a hunch it might be dying. Just sayin'.

Thanks for your response.

 

Right? I am learning as I go on the Prius battery issue - earlier today I ordered one of the Optima ones you suggested. I think while the car is down I may skim through the Priuschat site and see if I can do a quick study in any other should-know tips before I get back behind the wheel ... just a crash course so I don't get caught like this on the future with other Prius-specific issues.

Thanks again.

 

So, what do you think the odds are of having a 12v battery that's totally deadsel, vs. having blown the inverter? Is there any way to tell besides changing the battery and not having it work? If there's a four-digit repair involved the car will likely be totaled out. Gah ... I've been having nightmares about searching for another Prius and going to a car lot owned by someone named Crazy Ed ... I hope it's not a self-fulfilling prophecy.

Thanks for your advice!

 

Yikes ... I left ex and neighbor in charge of jumping ... the end of times may be near.

 

I got the new battery in today's mail, read the instructions, watched a video about how to change the battery, and decided to do what I could to get ready before daylight fades. I removed the battery cover and the black plastic harness, and saw that there is standing water in the well where the battery fits. I can't tell how much since I don't know what it looks like normally in there ... the water is touching the old battery. What should I do? Proceed? Take any special precautions? I don't know enough about this kind of thing to make a confident guess.

 

Thanks, I was just looking this over in the threads! I am trying to find more about a possible plug that I could unstop to release the water, that I read others asking about. Is that right, or do I need to bail out the compartment manually for the time being?

Thanks again!

 

Sorry to keep hitting everyone up ... is there a good video out there to take me through the steps of changing out the battery? I've been searching, but I have a cold and a babbling toddler and can't really concentrate with the congestion and 100 dB conversation.

Thanks in advance!

 

I can't find one with the complete process (that I could tell), and I'm not really able to search effectively right now ...