Parasitic battery drain?

Good Grief....
"More than few days...."???

Au contraire....
I routinely let my Gen3 sit for WEEKS at a time. I hate burning that smelly stuff so I wait to use the EV for any daily shop-op trips.
I break it out of its slumber when I have a long trip, such as a well paying courier gig or a vaca to warmth.
NO PROBLEM FOUND.

Good Grief...
How can you be such an Apologist for toyota's horrible implementation of a PHEV?

"All you got to do is take a 'regular long trip every other day' ???
You can't be serious.
That is a time consuming, gas consuming, CO² producing, WORK AROUND, for a +$35k PHEV.

Or,,, "You should Plug in your Prime two times, at two different ends of the car, if you're not going to use it the next day."
You can't be seriously telling people that's how you should operate the Prius Prime.

What's so hard about engineering any PHEV to keep the pack at a happy temp range and the 12V battery charged to a normal level ,,, while plugged in? Regardless, no fine print.
I suspect every other EV or PHEV does this without any WORK AROND on the part of the owner.

A lot of EV's that I know of will keep the pack temp and the 12V battery happy while not plugged, but only down to a low SOC.

After reading this thread I guess a Gen5 Prime is off my list. I'll just have Gasket Masters repair the head gasket on my '10 Gen3 with only 167k miles on it. Another engineering mistake on toyota's part.

 

The dealer full charged my battery after it drained a couple times. It's been fine since in my 2024 model.

I think what happens is that the car just doesn't put the 12v at a high SoC easily, at all. It died on me *after* a 700km drive at one point. But since the full charge at dealer, the 700km return drive, it's been fine.

So, from what I gather, the gen 5 seems to be able to *keep* the battery at some sort of range from wherever it is. But the moment it drains down, whatever the car does to keep the 12v "topped up" is exactly that. It must be some sort of capped "top up". So you'll almost never get out of the 12v SoC dangerzone unless you intentionally charge the battery with a battery maintainer after that.

This is the best guess I can make. The 12v tests done show I'm still at 90% of the original CCA and total charge 2 months after it was on the battery charger in December at the dealer.

Mind you, the moment it dies again, I'm getting a new 12v under warranty and then once the warranty is over, if this happens again, I'm grabbing an AGM rather than flooded cell. Which is something many EV owners do as well. This isn't a prius specific problem. I think its a general hybrid/EV problem now that the 12v put in the cars keep getting smaller, and the total number of electronics in cars too.

I'm not going to go as far as plugging in a battery maintainer every single day unless I was only driving once every 2 weeks for 10 minute round trips. But if you're driving that little, even a traditional ICE can benefit from being plugged in when its cold out.

 

In my experience DIY’ing this sort of CCA testing (with a Clore Solar BA5), with various cars, the test CCA on a “good” battery is invariably higher than spec, 10~20% more.

A 325 spec battery might test 350~360, for example. If instead I’m seeing lower, say 290, it’s on its way out.

 

If that's ok with you, bless your heart.
Someone that wasn't ok with that experience could easily let the 12V die a third time and it's Lemon Time!
Your 12V was too low to boot up a hybrid, twice. That can't be good for any lead acid battery.
Most cars keep the 12V battery happy, Gasser or EV/Hybrid.

Care to reference this statement?
*below

EVs / Hybrids use the 12V to boot up the system. After that the 12V battery is along for the ride.
It doesn't care about 'number of electronics'. The DC to DC converter is powering the 12V bus when ON.
What matters is the 'Keep Alive' current, when powered OFF.
The RF receivers and who knows what else. All cars have some.

The 12V battery in my '17 Bolt is the original*. Last summer I heard of a few failures on really hot days and that got me nervous. so I bought a replacement. The new battery is still sitting on the floor. I put a batterMinder, with the anti sulfation function, on it maybe once a month.

 

Well they won't replace it if it tests good, but when it dies again I'll be able to point to it as being bad. But until then, I gotta wait it seems.

Also, when I say its not just a prius problem, its because it appears to be happening to a lot of 2020+ EVs and plug ins from what I read online, that the 12V batteries are just failing way more than in regular cars. There's surely, something, at play that isn't as simple as being a pure gen 5 prius problem. They've probably just pushed the "it doesn't need to be big" too far in various engineering departments for the automakers. So once they lose charge, recovering charge is much more difficult.

There are also a lot of monitoring systems, telematics, wireless connectivity for apps, etc. More and more of these features are increasingly common and each one is going to be drawing on the 12v in the car. Most cars, from what I understand, disconnect their traction batteries when the car isn't being charged, and isn't turned on, to avoid an active high voltage system being on. So all these accessories draw from the smaller battery. At some point, this must all add up to cause issues. More demands on the 12v when the car is idle and parked, paired with smaller 12v batteries, they probably drop below the usable voltage more often.

 

Could this all (or mostly) go away, if the manufacturers put in some flash drives, or maybe more flash drives. I'm not sure, but thinking a fair bit of the phantom draw is to power volatile memories. Only solid memory currently is the odometer number, if I'm not mistaken.

[Just had a minor earthquake here, no kidding]

 

1. Why is this? References? A bigazz Gasser has similar 'Battery Hot' loads with all its various RF receivers. Every car seems to have these now.
2.Seems like simple math to me. X Ahr load during power OFF requires X Ahr rating on the 12V battery.
3. "more difficult" ? Why is this? Charging a 12V any Lead Acid is a simple thing.
It's been done since the early 1900's. Again, simple math.
4.Again, simple math. If the cell phone service, wifi, and key fob RF receivers (missed anything?) and the few 'Keep Alive' systems are using X amount of power, at X amount of time the 12V battery will start to get low.

And if this car is an EV/PHEV and plugged in to a J1772 there should be NO Issues. And the HV Pack should be at a happy temp, for extra credit!

Some cars will actually 'Load Shed' and turn off some of these systems to conserve enough power in the 12V to boot up the car and get the HV battery online. And then the 12V battery is just along for the ride.

Evidently the SW controlling the 12V SOC is not that considerate to the Prime owner. Thanks Toyota....

 

Some of these answers have to do with emission/fuel economy regulations or costs. They may have a small impact individually, but the manufacturer is making many such decisions that add up.

A battery with less capacity is lighter in weight, and lead-acid is still cheaper than switching to Li-ion. Charging the starter battery takes energy that is coming from the fuel that moves the car, so the system won't charge it to full every time. Even if it does want to charge to full, that isn't going to happen if the car gets to its destination first.

Shedding load only goes so far when starting with a small capacity battery.

As for plug ins, the j1772 standard includes safety features. One of those is to only energize the cord from the EVSE to car when charging the battery(or cabin preconditioning, or the battery thermal control). Maintaining the starter battery isn't a high enough load to warrant powering the cord, and the communication line can't carry that current. There are strategies to get around this limitation, but it shouldn't be needed if the battery was sized correctly for all the loads.

Full feature thermal control systems for the battery cost more. Having that engine means a PHEV isn't totally dependent on the traction battery to get around. So many PHEVs opt to not have the full feature system, with a heater only installed for freeze protection.

 

1. Charging a 12V is not rocket surgery. Just do it. Especially in a hybrid where the 12V never sees the high current draw of a starter motor, just a ~20A blip to boot up the car.
If it's a PHEV, there should be nothing to talk about.
If it sits many weeks the load shedding should kick in accordingly. If the Prime is discharging the 12V battery to the point of being dead,,, Toyota is doing it wrong. No excuses.

2. "Strategies"? Like having the EVSE power up to maintain the 12V SOC and the HV pack temp?
Most EV/PHEV do this.
The Prime seems to fail at this simple task. Plugged in or unplugged. Failures are reported. Unacceptable.

3.. Yes, a proper TMS costs. Some PHEV's have it, iirc. The Volt definitely did. Some people live where it's needed.

PS, I'm just pizzed. My Gen3 has a failed head gasket at 167k miles. This is a common and chronic problem.
But it never had a problem with the 12V discharging when I left it for more than 3 weeks often!!!
I was tempted to just sell it and upgrade to a Gen5, but they're so expensive...and you can't leave them alone.
So I'm having the head gasket replaced and I'll just stay the course. (I really wanted to use the Comma3.)

 

Not going to say it. Sucks though.

 

Go ahead and say it ...

I thought disabling the EGR would stop the uneven combustion temps and pressures due to a few clogged EGR passages in the intake.

It sucks also because if it were a Corrola or any other car they offer, it would still be purring along, WITHOUT requiring Off-the-Book maintenance that only geeks here and other forums would even consider.

But I wanted to burn the least amount of that smelly stuff, so a Prius it is!!

Now I wonder has a FelPro head gasket ever failed in the 100-200k miles range...

 

I’d get the Toyota Gasket Kit. If it’ll assuage your concerns: the head gasket has apparently been revised. Also, it’ll have all the rest, the gaskets, o-rings, seals. I’ve heard the aftermarket kits are nowhere near as complete, and mostly “this’ll do”.

 

NOPE.

"Fool me once................. Ya' ain't gonna get another chance.", "W"

Good Load, that link sounds like an engine rebuild minus the Mains.

My engine is in great shape. 1/4 qt oil used in 5-6k miles. But it has the chronically failing head gasket and there is no way I'm going to give a stock one another chance, not when FelPro offers an American Engineered 'problem solver' head gasket replacement.

I understand some have 'brand loyality',,, until they don't...

 

Yes it is, but a handy source for parts numbers. There may be later revisions, but it’s a good start.

Dismissing the viability of the Toyota gasket (and its revised) may be “shooting the messenger”?

I won’t mention it by name, but I would also ensure a certain system is thoroughly cleaned and functional.

 

Yes, yes, my EGR will be clean and functional. But for how long?
With my oil consumption the way it is, how often do I have to do all of this off-book maintenance of cleaning the EGR system?

Once it's clean and working, that is the perfect time to see if I can measure any difference with and without EGR! Can't hurt, right?

 

I wouldn’t go further than 50k miles.

you’re picking up what Toyota dropped, but barring a class-action lawsuit, whatyagointodo.

 

Apparently the lawyers don't think a hg blown after 100k miles is a safety issue juries would agree with. 99% of the time the engine keeps running. How they won the inverter suit was sudden failure as I experienced. Even the brake boosters have escaped class action since they have a limited braking failsafe.