12V Battery Died after a surprisngly short time...

Yep, it's an issue and with the Shelter In Home a lot more people are not driving.
Basically the Prime has systems that never sleep and use the 12 volt battery.
Things like Engine Immobilizer, SOS, Smart Key (if not disabled), probably emission
related canister purges and the like. It's like Pinkerton's motto "We Never Sleep".
Things you can do going forward is put the car in READY mode for an hour every week.
Plugging is the wall charger will not keep the 12volt charged after the charge cycle completes.
or
Get a battery maintainer/smart charger and leave it on and attached to keep your battery charged when
you're not using it.
or
Disconnect the Negative 12volt battery lead (which may have side effects).
or
You get the idea.
If you searched the forum before posting you'd see there are (more than) a few people
having this issue.
Is it a design flaw? I think the Jury is still out on that. You'll find opinions on both sides.
J

 

What @schja01 said. Plus, unless they are abused, car batteries age and weaken gradually rather than performing like new and then suddenly dropping dead. Mine is the same age as your's I don't think I'd be comfortable letting it sit for six weeks. One week has so far been the longest and it was still over 12V, but I doubt if it could have gone for another five weeks.

My wife's battery got too low to make the door locks do more than grunt last week. We got [edit for clarity] it the car 4-1/2 years ago and I'm not sure how old that battery was at that time. I think it sat for about two weeks and she'd been making shorter trips. But now, when she runs an errand, she puts on extra miles to make sure it gets charged back up. It'll be due for replacement before too long.

 

With what's going on, virtually all my trips are local, so I use my Spark EV and let the Volt sit. To keep the 12V battery up to snuff in the Volt, I keep a solar charger plugged into it.

 

I don't think it is the battery quality per se. Yes, there seems to be some batch of poor quality batteries in some PRIME. But from what I have read on others reporting here, it is not a single brand of battery Toyota uses on their cars. Much like OEM tires, they tend to use several brands of the same spec manufactured by different makers.

That being said, there is no denying that modern cars, not only PRIME but also most other computerized cars use some amount of battery charge even while parked. I have been closely monitoring my brand new 2020 PRIME's healthy 12v battery and found that it does deplete ~0.04v/day or ~0.3v/week. If the battery is fully charged with a smart battery charger, it will go up to ~12.7v, but ~1.5hour of driving will charge the battery up only to ~12.6v. It does not matter if the car uses the engine or not, 12v battery is charged from the traction battery. I see the charging starts as soon as the car in on READY on EV mode. Charging the traction battery with EVSE does charge 12v battery, but only at a floating charge to maintain the current level of SOC and only while the traction battery is being charged. Keeping EVSE plugged in for a prolonged time will not maintain the 12v battery. Without battery maintainer, even a healthy battery will drain below 12.0v in 6 weeks and is too weak to start the car.

See all this discussion here:
12v Battery Is Discharging, Re-Charge Now ! | PriusChat

 

[mention]stevepea [/mention] I’m not convinced the battery is at fault here. Even a poor old battery would last longer than 6 weeks unused and it would start any other old car. The problem here seems to be that the Prime drains the battery more so than any other car while not in use.

It took my Prime just one week sitting unused to drain my 12V battery, so what I get from [mention]stevepea [/mention] is that he found out his Prime’s battery was dead after 6 weeks, but who knows for how long the battery had been dead? It might’ve been dead after the first or second week.

So a couple of days ago, I had to jump start my Prime. What’s interesting is that I could not open the trunk or even open the charger port door because the 12V was dead. So there I was with a traction battery full of charge, more than enough to do what I needed, but I couldn’t use it because the 12v battery was dead. I think that’s a monumental design flaw. There should be some override button that allows you to take advantage of the traction battery to start the computer and the car itself in case the 12V battery dies. Or at least, give us a way to easily open the charging port so at least I can plug it in and charge the 12V battery using the EV charger. I know you can open the charging port lid from the inside using a tool, but that is incredibly difficult if you can’t even open the trunk!

But it is what it is. In light of this, I think I will purchase an emergency charger so at least I can start the Prime if this were to happen again. Now I know that every couple of days I need to go out and start the Prime for a few minutes to keep the 12V battery alive.


iPhone ?

 

One solution:

The Hyundai Ioniq Hybrid uses a 12 volt lithium-ion battery instead of a 12 volt lead-acid battery. ... A reset button on the dash will connect the HV hybrid battery to DC-DC converter and then recharge the little li-ion 12 volt battery, as long are there aren't any other problems.

but

There are downsides of course. The lithium-ion battery is sealed under the seats in the same unit as the HV battery. You won’t be able to use your Ioniq to jumpstart someone else’s car. That also means it will likely cost much more to repair or replace than a conventional battery, and longevity is an unanswered question.

August 2019 .. Missing Lead Acid 12 Volt Battery in Hyundai Ionic

 

LOL.... there’s another design flaw! Why the hell you want to hide the 12V battery? Geez!

But yeah, I was just speculating, but it makes sense to add an emergency charge button if the Prime drains the 12V battery so fast. It’s quite an oversight.


iPhone ?

 

After it was already 3-4 years old.

IF.....this model is one with a conventional wet cell battery located in the engine compartment, that is about what you should expect.
Replacing it with an AGM should get you somewhat longer life.

Bottom line, however, is that the onboard charging system probably never REALLY gets it full and sitting at less than full is hard on them.
A smart, automatic tender type small charger is highly recommended when it sits more than 2 weeks unused.

 

The EV1 actually had a button to push that would allow the traction battery to charge the 12V battery, in case of an emergency.

 

Yeah, I'd rather have easy access jump points front and rear under cosmetic pop off covers. KISS

 

So the Prime won't even start charging the traction battery from the EVSE charger if the 12V battery is dead. I call that a design flaw. I realize that is a subjective assessment because someone decided to design it that way for a reason. However, if that purposeful design leads to malfunctions that you have to jump through hoops to resolve, when there are existing ways to make it easy to get out of a dead 12V battery situation, then yes, I say that is a design flaw.

 

or a cost saver

 

Respectfully disagree 100%. There are no hoops to jump through. Just do what you'd do with virtually any other car with a dead 12V. Why do I want to pay for the factory to install a bunch of expensive circuitry that I might use twice in the life of a car in order to avoid using the 12V battery charger I've already had for ages or my newer booster pack? Makes zero sense. If they did offer that as an option, I'd say no. It's already handled and for a lot less money.

Put the engineering effort and money into fixing things that need fixing like that stupid 11.6" display glare, the blinding reflections from the lower dash, and put buttons back in where those silly capacitive touch "buttons" are.

 

I agree with the buttons. I want clicky buttons which give tactile feedback. Without feedback you need to look at the button that you press. That is also why I dislike climate control operations through a touchscreen, I want to turn a dial and press a real button.

This was the best satnav input system I ever used in any car:

 

What car is that "joy stick" control from? Is it for a nav system only? How do you input address in the system, I supposed that part had to be on screen.

BTW, physical buttons on climate control is one big reason I downgraded to LE from Premium.

 

BMW has/had one. I found it difficult/ unintuitive. Not my car fortunately.

 

I agree with the touch buttons. I would be ok with a smaller screen to make room for dedicated buttons.

But my point about the battery emergency override, I think I would use it more than once in the life of the car. I can imagine going on vacation and leaving the Prius parked for days at the airport lot and come back from my vacation to a dead battery. The point is that because of the nature of the Prime, a dead battery is more likely to happen than other cars, so I would gladly pay for an emergency override button if it was an option. It’s much quicker and easier than having calling someone to help you jump start the car. So, since we don’t have an emergency override button, I’m just buying a jumpstart pack and a battery smart charger/conditioner.


iPhone ?

 

Don't get me started, about ergonomic eyes-on-the-road controls. Even my screenless 2010 is dreck...

 

The BMW idrive system has unfortunately migrated over to Toyota. BMW makes the entire drivetrain for the new Supra.