12V battery going dead

True, but....

I'm not sure what you're looking at, but it's there in the EU manuals. Maybe not present in the US version? We're dealing with a Canadian here (maybe that explains some things).

28850-K0010 SENSOR ASSY, BATTERY STATE

(It's not "molded into the battery" though, so yet another incorrect conclusion being drawn about it being a special magic battery.)

 

The diagram and photo are pretty clear. It's obviously clamped onto the terminal, and not part of the battery.

The 3-pin lead is bringing in 2 12V lines from the fuse box, and sending an indicator out. It's comparing terminal voltage to the rest of the 12V system.

Somehow that doesn't surprise me. You're really good at figuring stuff out.

 

Exactly. That connector/sensor is part of the negative battery terminal. It comes off when you pull the terminal off. It's not a separate sensor within the battery itself.

(I know you already know this. I'm mostly speaking to any silent crowd that are watching this trainwreck of a thread. I'm just trying to make sure nobody else gets the mistaken idea that you can't easily replace the 12V battery in a Prius Prime. I've seen misinformation like this take on a life of its own on this forum more than once. Someone says something incorrect in a thread and is corrected about it, but a completely different new poster reads it and repeats it a couple months later.)

 

Here's a product page from Bosch explaining what a battery sensor is:

Electronic battery sensor

Basically the same idea as this one.

 

What you want to do is a series amp monitor while shutdown. This is a definitive test and allows you to track down the parasitic draw which has to be large if it kills the battery in two hours. A $5 Harbor Freight meter is good enough.


This technique with the negative jumper removed in step 4 reduces wait time for the computers to reach their powered down sleep states.

In your case I would start with the 10 amp scale.

Typically most cars have a 10-30 ma parasitic draw when shutdown and not charging. Under 50 ma is usually considered good enough to last 3 or 4 weeks with a good 12v battery. If you have a low draw it has to be the battery.

Otherwise Toyota should find and eliminate the excessive parasitic draw. Any local mechanic can do this if you would prefer not to do it. It gives evidence one way or the other.

 

You do know the metal bits are conductive, right? If it's not attached to the battery terminal, how do you think the ground lead attached to the sensor is attached to the battery?

 

Apropos of nothing, always loved this sketch.

 

Actually, maybe if you've got a special battery with something molded into it, rather than the standard battery with the standard Prius battery state sensor as shown in the diagram (which matches your photo), maybe that's the problem?

Your battery sensor is missing!!!!

And you've plugged the connector for the battery sensor into your special battery temperature monitoring port!

No wonder it's confused.

 

Oh, for completeness, I should have posted the circuit for the sensor earlier along with the parts diagram. Here it is.



(The direct electrical connection of the sensor to the battery terminal isn't shown as part of the car's circuit diagram...)

 

What you don't understand is that the part you think is part of the battery is actually part of the terminal.

Don't believe me? Do this simple little test.

Here's a pic I took a while back of the negative side of my battery:


Does that look familiar?

Now go to your battery and take off the top nut; the one right under the big label.

Now pull up on that whole section with the plug.

See how the section with the plug is part of the terminal and not part of the battery?

Seriously. Try it and report back.

 

Listened to people, taken in information and tried to figure out how things work. Rather than forming misconceptions on the basis of no evidence, or even contrary to evidence, and continue to insist on those misconceptions when presented with evidence.

If when presented with evidence contrary to your misconceptions all you take from it is "you're wrong 'cause you're wrong", you're wasting your own time as well as everybody else's.

You can look stuff up for yourself in manuals and parts catalogues, like I just did to check the battery sensor situation.

That does sound potentially plausible. Personally I'd just disable the DCM - I believe you can do that by calling the operator from it in the US. Maybe the same in Canada. They send a command to shut it down remotely. (And then it needs a dealer/scantool to reactivate). But I don't use/want any over-the-air functions.

 

OK, the battery sensor you circled, found in both Gen 4 and Gen 5, is a separate component and not part of the battery. It will come off when you remove the negative terminal.