PSA: Don’t get Dorman Products replacement Hybrid Battery (Also, help? P0AC0.)

Start with the easy stuff first. You mentioned above it could be the 12 volt. Nail that down .... Is it the 12 volt?
Take a multimeter / voltmeter and get the volts for a few times before you start the prius.
Leave the hood open and recheck the 12 volt batterys voltage after the prius is running. And write them both in a log. Take notes. The car behaved like this! Date and Time Anything else you think of too.

That's the easy stuff, get that done first.

Now the shiznits.....
Just so you get a feel for what's possibe take a look at the P0Axx error codes POAC0 is there too....
It's the Prius Traction Packs Current Sensor (but you probably already know that if you looked)
OBD diagnostic of Auto: DTC(Diagnostics Trouble Codes) P0Axx

There are Toyota sub codes for POAC0
and here are two of them I found.
P0AC0-123 - Toyota Diagnostic Trouble Code (DTC) Definition, Causes and Diagnosis
and
P0AC0-817 - Toyota Diagnostic Trouble Code (DTC) Definition, Causes and Diagnosis

If you know how to get pink codes bu shorting 2 pin of the ODB2 connector socket - get the blink codes and the sub codes currently set in your ECU(s)...
Be Careful ..... shorting the wrong pin holes in the ODB2 socket can blow big fuses or worse....
Besides, while looking at the ODB2 connector socket you are usually looking at it upside down and backwards.... Have the detailed diagram of the connector and the pin socket locations with you when you are putting in the clip.
search how to get prius blink codes.

And here's a Toyota TSB from 2009 that should help with narrowing down the issue(s)
http://media.fixed-ops.com/Toy_ServiceBulletins/sb0166t09.pdf

The links are just as much for the tech guys here willing to pitch in as for you.

 

Thanks for the kind words... In my experience this problem leads me to where the voltage sensor harness plugs into the Hybrid battery ECU. That plug gets corrosion and the Toyota Stealerships will say $800 for new ECU and $3K for new battery pack. But you can also get in there and just clean up the mess and make sure nothing has shorted out yet. Worst case scenario you put in a new $50 voltage sensing harness (Wire Frame No. 2) and a used ECU for $100. But try the cleaning and inspecting option first.

 

The current record as reported by a PC member for dorman replacements by one owner: six!

Once I quit messing around with the very labor and time intensive process of rebuilding and maintaining a failed pack and got a new OEM for my 06 with only 50k miles three years ago, all my reliability and drivability issues disappeared.

FWIW

 

I usually pull the ECU and take off the cover to confirm nothing has shorted out where the plug socket attaches to the circuit board. Then I use a tiny piece of sandpaper to sand the corrosion off the pins. In many cases the the plug and socket will have fried the pins and melted the plastic and you have to replace everything, but hopefully you're addressing this before it's turned into that problem.

 

my recommendation is a techstream subscription so you have access to the repair manual.
https://techinfo.toyota.com/

I got the repair manual a month after out first hybrid. I didn't use it for 8 years, but I've been using it now for 7.

Video's are great, when you can find one that makes sense to you. I wouldn't dig into the traction pack or the hybrid system without the manual.

 

Any advice that suggested getting a used hv battery was terribly wrong. Even if it has a painted case to make it look better. Even if it is reconditioned, rebuilt, guaranteed or reconstituted. You can't change the laws of physics or chemistry.



All of those options lead to regret and rework. You can't trust your car because reliability is gone. If you insist on diy disassembly / reassembly to save money and get an ego boost, buy new cells.

Be careful of scammers right here on this forum. They are plentiful and some are well known members.