Installing a panel meter

Use a fog light relay to short out the ammeter whenever your Prius is powered on.
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JeffD

 

How is a permanently installed ammeter better? You only want to be measuring current when the car's completely off; seems to me this is best done with an ammeter temporarily installed in series.

 

On the 12v circuit you want to measure there is no cutoff switch, relay or similar to bridge across. The fundamental issue is the parasitic draw you want to monitor is always flowing to certain loads which are designed to be on while shutdown. Including the smart key rf interface and various other constant on circuits which are needed to run evap tests and start the hybrid system.

You could place a high current shunt in series with the 12v battery circuit at the battery. However a shunt capable of carrying maximum running current is less accurate at milliamp thousands of an amp currents. Same goes for inductive coils in dc service.

If I could not wait for the Toyota solution which is sure to come, I might invest in a lithium 12v battery with built in reserve battery controlled by a remote. Or for less money I might install a second standard 12v battery with a smart rv style voltage monitor/isolator which can be remote controlled with a simple switch to provide backup power.

Even less costly would be a lithium jump pack with a constantly on power connector wired into the cabin for convenience. The lowest cost solution for a car not driven every day (with an excessive parasitic draw) would be a $40 battery maintainer wired to an external quick connect such as comes standard with the Battery Tender Jr.

 

so the software update didn't work?

 

Can one of you parasitic drain people just buy a multimeter and source the general location of the drain already?

Seems like you guys will do everything EXCEPT buy a multimeter and test which fuse is pulling current while the car is off. I'm truly curious what it is and I don't own a Prime and as such do not suffer from this issue or I'd be out doing it myself. It's just weird that NONE of you are willing to do the basic task of tracking the drain.

 

I've been an Electronics tech for a while, but I'm struggling to figure out exactly what you're up to with this "problem..."
Why in the world would you be having this issue on a car that is zero years old?
Does Canada have warranty laws that would cover this?
I would mention Toyota of North America - but I'm all too aware of their corporate culture!
HOWEVER (comma!)
Much as I have been a justifiable critic of Toyota's stealership network, I'm going to be on THEIR side if they deny a warranty claim because one of their customers hacked into the electronics of a model year 2024 car trying to chase down a "parasitic??" battery draw with panel meters and gosh knows what else.

What do you mean by 'parasitic' (as opposed to NORMAL) current flowing from the Aux battery?
How many Aux batteries have you had to put into this car?

I do not know much about the G5s but my presumption is that they have the same miniscule aux (12v) battery in the back of the car that we've all come to know and hate in the G3s and G4s. This is basically the same type of lead-acid battery technology that Alex Bell was using 150 years ago when he cheated Elisha Grey out of the telephone patent. The AGM (absorbent glass mat) just keeps the acid from sloshing around in the battery so that you don't have to yell for your lab assistant over the phone.
The Aux battery doesn't 'start' the car but rather it boots the car up so that the larger (traction? main?) battery can start the ICE (or not.)
This is more of a voltage thing than a current thing but even the dinky little aux battery can pop the fuse on a multimeter - many of which are only rated for about 10-ampres of continuous current over a certain time period, which is why multimeters don't have to have connector leads that look like jumper cables.
You can use a 'clamp-meter' only this (like your panel meter idea) will only give you a snapshot look at what is squirting out of your battery when you're not looking.

SO.....
Prius people tend to be a little more anal than the average folks out there and this problem evidently bothers you enough that you started a thread about it so I'm going to break with the forum custom and actually try to answer the question now that I've questioned the question.

What I would do if I woke up in your shoes is give them back to you.
Then I would use something like a battery monitor, sometimes called a battery monitor meter with shunt.
They use them in the POTA (ham) radio and RV world for solar and battery ops.
The CHICOMS make some that are cheap enough to chase after your firefly and they can be installed (BY A COMPETENT PERSON!!!) in such a way as to not be a permanent wiring modification to your car - maybe even in Canada.




If nothing else it will give you a cheap project to work on while you're trying to go after Toyota to reimburse you for all of the 12v batteries that you've neem buying for your 2024 Prius.
Good Luck!

 

Good Luck!

 

the first sentence in you first post is confusing.

what symptoms make you think it is sensitive to voltage drop?

and what makes you say that it is unfortunately prone to erratic parasitic drain?

 

Perhaps, but I've never been much of a believer in the "Accidental Universe" theory.
I understand the plight of agnosticism, perhaps the most honest of 'beliefs' but I have always felt that atheism is it's own religion.
My mileage.
Yours, obviously, will vary.

We have a political sub-forum if you want to go deeper where proselytizing is more widely tolerated.
This is necessary because people cannot even talk about what beer they drink in America or how often they change their oil without things devolving into insults and thread removal.
That means that we'll have to leave that part of the discussion with you being you and me being me.

80's rock teaches us that there is a Highway to Hell, and a Stairway to Heaven.
That means if I'm right, a then we have a clue about the anticipated traffic patterns.
If I'm wrong then....well you already 'know the thing.'

Good luck with the car.