Okay. Who HASN'T had a 12V battery issue with their 2023-24 Prime?

The only "accessory mode" that could be useful is the "my room" feature when its plugged in and turned "on" but not in ready mode. Lets you have zero worries about the 12v but allows for heat/cooling, and other stuff to all run without turning the car to actually on. Could be helpful if you go to a store with a 1772 charger and want to leave the heat/AC on if someone is waiting in the car for you to return, for example.

 

Don't plug in the car when it's in Ready mode, it'll shut everything down. I'm also not sure if you can lock the doors via the fob in My Room or if it's like Ready mode and you need to use the physical key to lock the car.

 

I meant more plug in and use my room, it's the best way to safely use ACC type mode

 

Folks:

After posting a few days ago that I had NOT had any 12V battery problems, today I had a dead12V battery!!!

The initial cause was mostly my fault. I have a ham radio connected directly to the battery and I left it on overnight. Not great, but in my defense, it doesn't draw that much power and shouldn't kill the battery overnight.

When I got in the car today it was clearly unhappy. It wouldn't get into ready mode and it kept on rebooting and then did some weird stuff like PUSH BACK on the brake pedal and spontaneously start the wipers (though very slowly!!). My ham radio has a voltage monitor and it was around 9.5V, so clearly not great.

Here is the weird part and how I got it working. Following the manual, I jumpered the car using that tab in the engine compartment. Absolutely no luck, no response at all, in fact the car battery got "deader". After trying it, the car wouldn't even power up enough to act weird. Completely dead. Yes, I checked polarity many times before connecting!

I had some errands to run, so used my wife's Gen3. While driving I realized that maybe there is an issue with that charging tab in the engine compartment. It is the battery that is dead, so why not just jump to it directly the old fashioned way? After getting back, that is exactly what I did. I jumped it from my wife's Gen3, it fired up and got going again. I let it charge for a bit and can power down and back up again normally.

I set up a service visit at the local dealership before that idea, but with a completely dead car, wasn't relishing getting the car towed. Now that it works, I'll still go in tomorrow but now ask why the engine compartment jumper doesn't work. My wife's Gen3 has that same tab and I've used it a couple times just fine.

This is an above normal panic as I take off to Texas Saturday for the eclipse, so not a great time for a hiccup. Hopefully all is good now, but just in case others are having the same issue, unless there is a good reason I'm unaware of, the old fashioned jumping seems to work when the jumper tab doesn't.

Lemme know if I did something dumb.

will

 

BTW: Yay on not needing to be towed, but the car seems to have lost most of its settings, so need to fix them all before my trip!

Some seemed to recover over time (15 mins or so), so wondering if maybe they were restored from "the cloud"?

Will

Will

 

here's the poll for anyone who hasn't voted:

12v-battery-issues.247845

 

Thanks for the link @bisco, added my vote.

Fun screenshot from my Toyota app as many things are scrambled as a result of the 12V power failure. My car has a few more miles on it than I realised!

will

 

I just posted some surprising data from a 3 day monitoring test of a prime 12V battery in another battery thread. A lot of what is being assumed is incorrect. 12V batteries aren't being charged while driving, and aren't always charged when charging the traction battery, and leaving it plugged in on a full traction battery doesn't drain the battery. But the algorithm of when & how much to charge the battery may be contributing to problems as it's not what ICE cars do. Check out my post on page 7 of https://priuschat.com/threads/third-day-with-new-car-dead-12v-battery-second-day-in-a-row.242574

 

OK, back from the dealer visit about the battery jumping not working and no surprise, left unsatisfied.

The initial "technician" got twisted in her own circular argument. She said the way she tested the car it passed all diags, so there was no problem. I pointed out I jumped it the way the manual said, so she started trying to argue the manual was wrong and so not her fault. The only difference between her test and the manual though was just a different ground point which is virtually guaranteed to be irrelevant.

I asked for a manager that was a bit more helpful who offered to have a *real* tech come out to my car and go over things. After the usual points on "did you really clamp to the tab" questions, this guy fully admitted that jumping using the tab in the engine compartment was iffy at best and said he jumps the battery directly quite often. Also in the "duh" department, said yea, lots of places to get a good ground. He at least verbally confirmed no concerns with jumping the battery directly. He did say that the tab was much less likely to work if the battery was "really dead". I said the last voltage I saw on the ham radio was about 9.5V which he thought should have been high enough for the tab to work.

Interpreting between the lines, I do wonder if there is some kind of low voltage lockout between the 12V battery proper and the jumper tab in the engine compartment? That would seem a "super-conservative" Toyota kind of thing to do. There was just absolutely no sign of life at all jumping to that tab, but instant results jumping to the battery directly.

I do need something to automatically turn off the radio when I turn off the car though. I'll ask that in the accessory part of the forum.

will

 

@REBobBecker: The radio I'm talking about is a mobile ham radio I installed myself, not the one in the car. All the car stuff shuts down as you would expect. Driven mostly by the need for the cleanest power possible for the high-ish power RF in a ham radio, the preferred practice is to hook it up to the battery directly and not use something like the cigarette lighter plug.

will

 

@Will B They sell modules that will cut off power at pre-determined voltages you could add to your ham radio or you could make your own with a micro controller.

You could also power the radio from the 12V outlet or even the inverter. I'm not sure how permanent use of the inverter would impact the car like having something always plugged in in it.

 

I do think I have damaged my 12V battery. Even on a multi-day road trip my ham radio battery voltage monitor is showing either 12.5-12.8 volts mostly (assuming this is when it's not being charged) or 14.x volts when its being charged. Then, on eclipse day I had the car just parked most of the day going in and out of it all day and it wouldn't start again at the end of the day. I jumped it and it was fine, but clearly doesn't seem to be holding a charge. First thing in the morning it is only showing 12V. That seems lower than it should be.

I doubt the battery voltage monitor on the ham radio is super-accurate, but even if off by a half-volt or so, clearly it isn't holding up anymore. I fear a new 12V battery is in my future and its my fault.

will

 

Okay. Who HASN'T had a 12V battery issue with their 2023-24 Prime?

...well, i've heard a rumor about a guy....

 

Touch wood - I have not had this problem with my 2024 prime. I never charge to 100% and take it off the charger an hour before full charge which leaves it at about 94%. No gadgets attached.

Lenovo TB-J616F ?

 

I have 4483 miles on my 2024 Prime. I bought it early Feb. No battery problems of any kind. I charge as soon as I arrive home each day. I leave it plugged in until the next time I leave. Average (modal) length of daily drive is under 10 miles. I have not depleted the traction battery (down to HV mode only) unless I was going on a 500 mile trip.

In most cases, you don't know what a 100% charge would be. You would NOT want to ever run the 12V or traction battery down to 0% at any time. My understanding is that the battery system manager will show 100% EV when it's around 80% charged and 0% EV when it's close to 20% SOC.

My guess is that the "charge just before departure" is to maximize the range of the traction battery. Li-ION batteries run down a few percent shortly after charging. You can minimize those losses by leaving the garage as soon as the charging completes.

 

After 8 months and 3100 miles, my 12V battery died. The dealer put in a new one at no charge and said the old one was probably defective. We'll see. I hope so. I will be checking the new battery voltage frequently via the diagnostic mode.

 

@Philip Frame : Sorry to hear that, nice you did get a new battery at least. I definitely "encouraged" my batteries demise by leaving a ham radio on for a couple days, but suspect it wasn't good either. However, since I did abuse it, I'm kinda stuck and will have to buy my replacement. I check the voltage each morning after sitting overnight and its now just a bit below 12V (11.9 to 11.8V), so I'm on borrowed time.

will

 

Since some are guessing, here's mine:
I think it may be over the air updates. I don't know how the technology works, but it may be using a band that is hard to pick up in some areas., like mine which is rural. This may require more power than in other areas.

 

There have been requests that Toyota increase power, but they go ignored