Is the 12v going? Need a 2nd opinion

Emery Cloth?

 

Yeah. You woke up my 2 brain cells, seem to recall Eric the Car Guy using the expression "crocus cloth". I got a roll of the stuff for a recent foray into copper pipe soldering (a first for me). It's 1.5" wide, dark reddish.

 

Optima has the worst reputation ever... Read consumer fraud and Better Business Bureau complaints about them. The Optima battery salesman who used to be on here even claimed that they resell bad batteries that are returned soon as they're done charging them up and they don't even test it. It's a big red flag when you're buying a battery that's dated last April. If I were you I'd get your money back on an obviously garbage battery and buy a brand new battery that's still on a shipping pallet and just arrived and not sitting on a shelf for 4 months because consumers no longer buys garbage Optima batteries anymore.

 

Maybe a phantom drain? If you have two wires with alligator clips and a multi meter, you can:

1. Open hatch and disconnect (and isolate) 12 volt negative cable clamp from body.
2. Connect one alligator clip to the disconnected clamp.
3. Connect the other alligator clip to a grounded bolt or bare metal on the body.
4. Run both leads out across the hatch threshold, drop the hatch closed. (you will need to crawl through the car to reopen, after)
5. Wait about 15 minutes, giving the car time to shut off all sentient stuff, then connect multimeter to the two wires, basically in series.
5. Set scale to amps first (for safety), then if no reaction switch to millamperes. With my third gen I read roughly 15~20 with occasional spikes to 45. If you're getting readings in the 100's, that'd be a serious phantom load.
6. If that's the case, try disconnecting fuses one at a time, see if the readings drop.

 

Apologies for failing to recommend a battery... (I thought I did). Batteries Plus most popular 12volt battery for wheelchairs and 12volt back up power supply for ~$130 is $100 less than the ones auto parts stores sell but has way more amp hours... Only challenge is you'll need some longer bolts and some bushings from your local hardware store so the battery cables connect properly. Here's the latest one I bought from them and put in my friend's Prius last June: Duracell Ultra 12V 55AH AGM SLA Battery with M6 Terminals

What's great about these batteries is they sell tons of them every month so you won't get stuck with a battery that's been sitting around for very long at all.

 

Likely correct but you haven't PROVEN that beyond a doubt yet.

Because the 12 V system includes more things than the battery itself.
Loose or corroded main battery cables are often a problem too.......sometimes a the end AWAY from the battery.

It is kind of sounding like your HV battery is failing or has an intermittent connection now.

At this point, I think you need a competent Prius mechanic to read ALL of the codes that it is setting and see if that matches any know failure.

 

Or get an OBD2 and use Dr. Prius and Hybrid Assistant apps to get more HV battery data... I just did a 8 mile test drive this morning on an '05 hybrid pack rebuild I did this Summer which is having error codes again and Hybrid Reporter app made 20 pages of charts and graphs out of the data from Hyrbid Assisstant. In this case the problem is bad voltage readings to HV cooling fan and because I installed a Prolong Harness, they're now sending me a replacement fan controller, which is the only reason I buy their harness in the first place and I'm still skeptical that's the only problem, but if there's a chance of getting an extra fan control box out of it I'm excited. Of course it's all a process of elimination, so we'll see.

 

There it is in pretty much pure form, the one uninformed notion that probably does more than any other to throw people off the track of their diagnosis by assuming that a combination of DTCs "makes no sense" before looking up their detection conditions and reasoning out how the combination does make sense.

One or two codes can point you in the general direction of a problem, but it's that weird group of codes that seems inexplicable until you have all the detection conditions in front of you, that often can eliminate nearly everything else but the correct diagnosis for you in one step.

Usually a better gift from the diagnosis gods than any of us has lived well enough to deserve ... so of course we walk it to the end of the world and throw it off.

Oh, don't worry, you didn't.

I'm sorry you went through that, but on the bright side, it adds to what we know.

Wait, what, you have Techstream? Have I seen any trouble codes posted in this thread yet? What are you waiting for, man?

I saw the first post said "nothing", with "the OBD2 scanner", which is the usual story when someone uses an OBD2 scanner that isn't Techstream.

Now, if you're connecting with Techstream and seeing no DTCs anywhere, the plot thickens. Can you screenshot the Data List from the ECM, HV and battery ECUs and post those?

I wouldn't worry about it. The car is protective of the battery; what you hear it doing on descent is exactly what it does to avoid any overcharging.

-Chap

 

It's not an uniformed notion, it's called wishful thinking/being optimistic... And sometimes no matter how misguided that may be it gives an opportunity, no matter how irresponsible it may be, to create the illusion of solving everything. Like the lady that called me asking about her college aged daughter who's been driving a Gen 1 with 270K miles on it. The red triangle of death has been on for three years and 60K miles and the car's running great. There's no way you're gonna get a cheaper fix than that. And how much you wanna bet they still haven't had the error codes checked even though I told them to do it right away?

 

Wishful thinking it may be, optimistic it may be ... but also at odds with what you find out when better informed, so I think the word was ok.

Anyway, often enough to matter, there is a cheaper fix than ignoring for 60k miles. If you read the code, determine the cause to be something minor that you're not concerned about and elect not to fix, and keep driving, you get the same 60k miles for the same zero dollars, but with lower anxiety, because you know what it is you've elected to ignore, instead of just clenching your teeth and hoping. There are various ways clenched teeth and anxiety turn into money.

Of course the possibilities also include that you find out it's something that makes you decide it's time to upgrade the car (and then you do that, instead of clenching teeth), or you find out it's actually something cheap to fix and you do it, and you enjoy the car for 60k more miles with no red triangle and no jaw clenching!

-Chap

 

Your average Prius owner is not capable of doing that......or properly interpreting the results.
Indeed, it would seem that most Prius "mechanics" aren't capable of doing it either.

 

If you stare at the data long enough you always learn new stuff... Most auto mechanics just want a work routine and not much thinking. Prius Chat nerds on the other hand...

 

........tend to be obsessive about EVERYTHING and over-think the most insignificant details.

Oh.....and often erroneously assume that everybody in the world has the skill and capability that they do.

Or is that "Often erroneously assume that they have the necessary skills......."

 

Don't forget about being prone to meandering conversations too...

 

it' snot the 12v?

 

"We'll see," he answered, phlegmatically.

 

So, here we are at 58 posts; only 6 of which are posts from the OP – the original post and 5 follow up posts.

Still waiting on the OP to post some actual codes, in order to progress towards a solution.

 

I think (in the trade) it is known as "sweating copper pipes"