Original factory 12V battery dead with zero warning

An agm with minimal load does this to all of us. I drove 30 minutes to a store and came out 20 minutes later and it was dead.

But I had a lithium jump pack ready to go and knew how to jump it from the front fuse box.




Anything over 8 years is borrowed time. Getting a free load test at the auto supply store would have told the story as well. But trying to get someone to spend $200 preemptively rarely works.

At least it was not a $2500 master cylinder or hybrid battery. Or a more expensive head gasket/engine. All too real with these years.

 

A regular car does not use as many electronic control units as a Prius.

Some of the equipment in the Prius V is connected in sleep mode when the car is turned off.
Thus, the battery discharges even when the car is turned off, unlike a regular car, where the battery discharges only when trying to start it.
The accumulation of a constant discharge during rare trips adds up and the battery gradually dies.
Its plates are sulfated. It would be correct to conduct periodic control and training cycles, removing the battery from the car for its training with a charger.

There are devices that are installed on a 12V battery and transmit information via WiFi to your phone about the decrease in battery voltage so that you can recharge the battery in time.
You can find them by searching for 12V car battery monitoring.

 

????
I'm not sure if you're trolling or asking a serious question..........

 

Mine died unexpectedly as well. No warning. Not that it offer help............... but the Tesla Model 3/Y 12 volt gives you a pop up error message that tells you the there is a problem with the 12v system, your car may not start next time.......4 hours later I was locked out. Gaining access with a physical yey involves popping out a round plug in the front bumper,applying 12Volts to pop the frunk then jumping the 12V battery which is just right of center under the windshield. They changed it in 2022 models to a 16V system with a Lithium battery in efforts to prevent this. A new battery you can pick up from Service centers for $90 and install it in about 15 minutes. Every 4 years just to be safe. I'm going to do this this Spring. I have another year on my Prius one...then it gets a new AGM one as well. I understand the frustration.

 

The HV traction battery is isolated until and only if the 12V auxiliary battery triggers relays and the inverter to 'start' the car.

 

Most car batteries die with "zero warning" these days.
Actually you usually DO get some kind of notice even if it's the fact that you're driving an eight year old car with a battery that may or may not have been replaced in the last 4? 6? or even 8 years.

BUT(!!)
Sometimes you really DO get little to no warning, because the aux (little 12v) batteries are getting smaller and smaller than the refrigerator-sized ones that they used to put in cars.
This is because you're not using a yuuuge battery to drive an electric motor to turn over a sleepy engine.
In many cases, you're booting up a computer in a car with far too many parasitic loads on the battery.

In the 1970's you'd get some hesitant cold-start cranks as a warning.
Now?
It's more of a voltage-level thing and it's binary.

Know what?
Tires also fail with 'zero warning' and so in many cases so people carry spares.
Well....most SMART people do anyway.....
For batteries we used to carry jumper cables.....but this requires another car and comes with the danger of popping a fuse, or doing some DC arc welding if you get things wrong.
If you buy your car from the wrong manufacturer you might even zorch something that isn't properly protected by a $0.59 diode, along with the fuse.

SO.....
Since we're now into the 2020's there is the 'Jump pack.'

Get one.
Charge it.
Test it. (See 'Folksy Anecdote: Below)
Done!

As a bonus, they're also REALLY good for charging phones, tablets, etc....if you get the right one.

Folksy Anecdote:
I keep a $100 Hulkman in my CFO's and a lesser budget model in my own.
One fine day I went to the aid of my daughter whose "Oscar Sierra" plan is to call her Daddy when the car doesn't start, and of course I grabbed the $100 'gucci' car charger that I had never used in real life, and OF COURSE it didn't work.
As it turns out, some chargers have a "Darwin" feature to prevent you from starting a car with a battery below a certain voltage threshold and I would have learned about this had I been as smart as I always think that I am.
However (comma!!!) I still had some old school jumper cables and so I only looked slightly foolish and learned the best kind of valuable lesson.
It stung the pride a little, but since then I ALWAYS test stuff like this out in advance.

 

How about this: The 12V auxiliary battery powers the electronics which call for the HV battery to start the car. No 12V, no call, no start.

 

Easy!
They're thinking that they want to sell cars and make money!
It's working too, because many people LIKE Toyotas.

The line forms on ME to bash Toyota for their corporate culture, but the v is actually a fairly well thought out car!
You'd be in the same shape with nearly if not EVERY other hatchback whose battery failed in service.
It just so happens that Priuses (including the station wagon model) use the Aux (12v) battery to boot up the car so that Robbie the Robot can tell the Traction (200v) battery to spin the engine and start the car.

Either way, if your battery fails in service, you still "jump the car" off the same exact way that they do with most cars now and the way they did it almost 100 years ago.
Open the car with a metal key.
Open the hood with a mechanical latch.
(hopefully) Connect the cables in such a way as to convince Robbie that there's enough juice to boot up the car.
Then replace the Aux (12v) battery.
Believe it or not they actually thought about this a little bit before they made the car.
If you DON'T do it this way then you run the chance of depleting the Traction battery.

THEN your car becomes a 3200 pound statue until it's towed to a dealership.

 

My CFO's usta-car is a 2012 GMC Acadia.
It died with 'zero warning' about 5 years into service with a dead battery.
The battery is behind the co-pilot's seat in those cars - and you're NOT opening the hatch until you sort things out.
OF COURSE it happened at a bad time, and this is what prompted me to buy and start using Jump Packs.

My baby girl's land barge (2015ish Yukon) did the same thing.
She drove to school (work) just like any other day, and that afternoon - nothing.
Dead Battery.
Even with new cars with old school starter motors powered by a 12v battery, if you don't have enough voltage, you ain't closing any relays.
Back in the day the only silicon in those old dinosaurs that we drove as kids was the sand that got onto the rubber mats when we went to the beach. A 12V battery back then with a bad cell may still show a normal open circuit voltage (OCV) of around 12.6vdc - AND its ability to deliver power under load (like starting a car) will be significantly reduced - but in those old cars all you had to do is turn a key and that would GIVE YOU all it had left.

 

Our original 2102 V Five 12V dumped after 7 years. Did the contortionist act to get the rear hatch opened manually. Bought the jump pack.

 

From memory (it can probably be found here on PC via search)... Grab a standard screwdriver, place one layer of electrical tape over the end to avoid scratching what happens later, climb through a door, over the back seats, into the cargo area, use the taped screwdriver to carefully pry open the trim covering an opening in the lower/center trim panel, use the screwdriver working end to force the rear hatch capture latch up and to the side until the rear hatch releases, climb out through your newly opened rear hatch, disassemble the cargo floor mat/foam panels on passenger side, access the auxiliary/12V battery compartment aft of the passenger wheel well, jump or remove/replace the 12V battery. Grab a celebratory beverage.

 

If you really want to understand the most complex car ever made, review the hours of university level hybrid transaxle videos on Weber Auto.

The Cliffs Notes version is the two electric motors in the transaxle have to be carefully synchronized to the engine, wheels and each other to run or even idle without creating horrible mechanical rattling noises. There are no torque converters, solenoids, clutches, chains or belts. To do so requires a symphony of ecus from the hybrid battery to the engine ecus to be fully awake and AOK for launch. In a Prius this boot and systems check happens between the time you press the button and READY displays on your dash. Until then it's all 12v battery. Even after Ready, all the computers (maybe 20) still run on the 12v but now the source of the 12v is the another amazing piece of engineering, the inverter converter (also detailed by Weber Auto).

The shutdown 12v parasitic draw is 20-30 ma (thousands of an amp). A normal Prius agm battery will not discharge enough to fail to Ready for three or four weeks. Just like every other conventional or hybrid car.

So why not just keep the ecus running enough along with the hybrid battery and inverter converter so the 12v is simply Ready all the time? Because your hybrid has a very small (not huge) nimh battery (around 1.3kwh) with no external charging capability. Only about 50% of that capacity is ever allowed to be used to extend the oem hv battery to at least ten years life. If it severely discharges it can be new hv battery time.

This car was sold as an economy car at a low price.

If you are still curious about the abrupt failure mode of your 12v battery, it broke a connection inside which caused the battery to go from at least 11v to your reported 0.12v. Sometimes a quick charge or jump will temporarily improve that connection until a bump opens it again.

Again, wait until real problems hit. You will wish it was a simple 12v battery.

 

Here's a simple explanation.

Your car has two very different and very distinct electrical systems.

One is low voltage (12vdc) which varies from ~12v to 14.5v when charging and supplies power to the fuse boxes, which distribute this power to key, electronics, electric pumps and fans, windows, door chimes, interior lights, exterior lights, etc just like a normal, non-hybrid car. This system wiring (as with a non-hybrid car) uses low voltage wiring, insulation and connectors.

The second is a HIGH voltage system used only for the hybrid drive system and AC compressor motor. This system uses a large, high voltage battery (202vdc to 270 vdc when under high charge). This system must remain electrically isolated from the rest of the car so passengers don't go zzzt zzzt sizzle sizzle. (Not to mention all the fuses and wiring that would smoke if exposed to 200vdc). The components in the hybrid system are designed with high voltage in mind, the wiring, the insulation, etc. In order to keep this safe, inside the battery case are two main relays, one connected to the positive side of the battery and one connected to the negative side of the battery. When the hybrid system is not being used, or a safety is triggered, or the car is off, these relays are open, preventing any high voltage from existing outside of the battery case. This keeps people from getting killed when they decide to work on the car with no understanding of the HV system, or if the car is involved in an accident and the hybrid system integrity is violated. The 12v system supplies power to the "key" system. When you activate the key and make the car enter ready mode, the car uses 12v power to close these relays and that is when HV power is applied to the hybrid system. The hybrid system inverter actually converts this HV DC voltage into a 3 phase AC voltage and sends that to the transaxle, which acts like an electric motor to move the car. When coasting, the electric flow is reversed and the HV battery gets charged. The inverter contains an additional auxiliary circuit (DC to DC converter) that converts the HV to ~14.5vdc for charging the 12v battery, similar to an alternator in a standard car.

No 12v = no power to any sensor that normally recognizes your key fob or key.
No 12v = no power to anything

You do not need to crawl into the back of the car to jump start. Open the door with the manual key, pop the hood and connect your jumper to the designated jump point inside the underhood fuse box. After connecting, or within a couple minutes, you should be able to just press the power button and the electronics will power up. Or, you should be able to just walk over to the trunk and open it like usual, since the fob sensor will now have power from the jump point. Once the car is in "ready" it will take over charging the battery. If the battery is too DOA, then no amount of charging will help and the battery will need to be replaced.

You have a lot to learn about your hybrid. This is the right place to be. If you don't take time to learn here, you're going to go through a very expensive learning curve at repair shops.