New prius Prime with dead 12v battery this morning

I am a few days late to this conversation. I had the EXACT same problem. Facts: same car -- 2017 Prius Prime, almost a year to the day from purchase w 14 mi, at failure ~6500 mi, the drive battery was just fine (100% charge) after we got the car working again, had not been used for about 10 days & I may have left the lights on but I have checked many times and the Prime (and all Toyotas so far as I know) turns the lights off after about 1 min. The anti-theft alarm does have some draw (incl. flashing red light at center console) but it ought to last a month, minimum, before that causes a dead battery.

I had a an emergency jumper cable/battery device in the "trunk" but, prii are totally different cars, so I didn't want to blow all the fuses or such if I made a mistake. So I unhooked the positive battery cable (may not be necessary) and used a lead acid battery saver/recharger which has always worked in the past. It took about 15 hours but the green light came came on the recharger. The battery has been normal since then. Of course, we lost our radio pre-sets, the time had to be reset, etc. -- so it's a real pain even if you can jump the car in 5 minutes. So it's going to the dealer -- I'll let you know what happens. I suspect a "short" but we'll see.

Oddly, the "computer" part of the car did "remember" how to bluetooth to my phone to get the time and maybe other information. The computer seems to be undamaged from having no juice -- as you'd expect. The "dumb" parts of the car needed to be reset. It's a real treat having to reset the console clock -- you'll need the manual. Why that clock can't obtain the time from the "smart" part of the car is a mystery to me.

However, the important information is that when the battery is dead, the prius is totally dead too. This means the doors won't open. More relevantly, you need to open the doors "to pop" the hood to get at the battery. Everybody ought to practice using the "old fashioned" emergency key inside the fob. You'll never be able to do it for the first time in the dark.

 

do a test on the lights shutting off. through gen3, they do not

 

so the car was running, then just died?

 

Here's been my experience. I previously had a 2016 Prius, also 4th gen which is in a lot of ways the same car as the Prime, just not plug in and doesn't have some of the features but they both sport the same type 12 V battery. Priii previously used AGM batteries which in hindsight might be more appropriate seeing that AGM batteries can be deep cycled despite being more expensive. In my 2016 Prius I had a dash cam and a often left my OBDII scanner plugged in, not a scan guage, just a cheap one from Amazon. Never had any trouble with the battery going dead.

I traded in the 2016 for the 2018 Prime Plus and since last September I've killed the battery 2 times. This is sort of bad news bears because they went back to a conventional lead acid battery (but still an EU size so still kind of pricey) killing the battery too many times will ruin the battery. I use the same dash cam and same OBDII scanner before and the battery goes dead in just 2-3 days, maybe it is the cold weather but I am skeptical seeing I never had an issue with the 2016 Prius and other people here and in the FB group are also seeing problems, weather it is days or weeks, something is definitely amiss. So yes, I can see how I am partly to blame, having things in the car that constantly draw current but, whether it is 2-3 days or 2-3 weeks, it is kind of unacceptable to have the 12 V battery die.

So one or two things are happening. Either in the Prime there are more "systems" that are running off the 12 V all the time, most which I would think would be common between the Prime and the regular Prius with a few exceptions. Or... we're all getting defective 12 V batteries with the Prime. One thing is for sure I have a feeling I , and others, will be replacing their 12 V batteries way before they should have to be replaced.

Someone posted that while the Prime's 12 V voltage sat at 12.6 V while charging and went up to 14.4 V while in "Ready"... I do find that interesting. 12.6 V should indicate a fully charged 12 V battery, or close to it. So I am curious whether or not the car is providing any charge while charging, I lean to thinking that there is and here's why....

I left my friends place to drop it off at a public charging station, found the car with a dead 12 V battery... I jump the Prime off and drive it 1 mile to the charging station where I left it to charge, thinking that the car will charge the 12 V while charging the HV battery. Came back and the car started fine with no issues or warnings about a low 12 V battery.

So here's what I am going to do, provided it isn't raining when I get home. I will park the car for an hour, let the 12 V battery "burn off" the extra voltage, they read higher right after shutting the car off, take a measurement, then plug in the car and measure again. If there is any sort of charge going to the battery there should be an increase of voltage, might not be the full pop you expect when the car is "on" but should be enough to keep the battery from discharging while charging the HV battery -- makes sense. I mean I rolled up with a weak 12 V battery that had only got about 5 mins of charging before I parked and put it on a charger....so something is up. Either that the car decides whether or not to charge the 12 battery when on a charger.

 

I'm eager to read your results. Sounds like the test I did on my PiP. With the EVSE plugged in but the timer keeping it from charging, the 12V read 12.67. Same as not plugged in. (This was after sitting for about 20 hours and releasing the hood from the passenger side door.) With the EVSE actually charging, it was 13.5V. Not as high as ready mode, but definitely charging. There are cooling fans (fan?) on the charger, so I imagine it's putting out the 13.5V to power that.

 

Check it out with a Solar BA5, or similar, one of the new line of electronic battery testers.

 

Ok so, drum roll, I have once again wound up with a dead 12 volt battery, this time left me with a mystery. I did not leave my OBD II scanner plugged in and actually haven't used it for some time now... I do have a Thinkware X500D dashcam which I also used in the 2016 Prius (non-plug in) which is mostly the same as in it uses the same battery from the bits and pieces I have come across (so if you know that the 12 V battery is different between the Prime and the regular Prius please say so). I don't know the draw from the dash cam but what I can say it never was an issue and I have it set to turn off at 11.7 V (or it just shuts off anyway after 48 hours).

So I drove to town and back, plugged it in, this afternoon, battery is too weak to turn the car on showing about 8 volts. I thought that's funny, it was plugged in. After I jumped the car off I found it also didn't charge. Everything is fine with the charger I later verified. So the only thing I can think of was the battery was too weak to imitate charging...or I did something stupid I am dealing with the flu.

So it's been debated whether or not the prime charges the 12 V while charging the HV battery. The answer is yes, it does.

While on the charger the 12 V battery read 12.56 V, immediately after unplugging the car the 12 V battery read 12.40 V, turning the car on (Ready) the voltage read 14.43 V.

So given that I never had trouble with the 2016 Prius and the battery and using the same accessories and that the Prime actually get's a little extra, I'd say I have a defective battery...or it's defective now. I don't see how the battery could pass testing at this point. I also think Toyota, as much as everyone complained, should have stuck with an AGM battery, much more robust when it comes to leaving something plugged in over a few days and it really doesn't have much of a current load at any point, they are more expensive but they're deep cycle.

So to clarify a few things:

Yes, the battery gets a trickle charge when plugged in and charging (if the car is done charging, it will not continue to trickle charge the 12 V)

The heat pump/AC runs on the HV battery and will not drain the 12 V battery, although cooling fans and such are on the 12 V system

The 12 V battery is required to both start the car (READY mode) and initiate charging. The simple reason is safety, prevents the HV battery from connecting to the rest of the car if there isn't a 12 V supply which might be damaged in a wreck.

The "cigarette" lighter or aux power both shut off when the ignition is off.

Don't leave your OBD II scanners plugged in (even if they're supposed to turn off)



...and now the fun part, taking it to the dealer.

 

iirc, the trickle charge is not as high as the pip. may not be enough if something has drained the battery too low.
it could be that your prime draws more on the 12v while off that your hybrid prius. you'd have to measure the draw while off. and the dash cam is enough to put it over the edge.

or it could be that your battery was one of the defective ones, and the dash cam put it ver the edge. hard to say without testing.

 

Check how much amperage is happening, when the car is "off". You hook up a digital multi-meter in millamps, in series, between the negative post and ground. FWIW, doing this I saw 16~18 milliamps, with spikes every 10 sec or so, to around 40.

 

I would assume that a 7 month old car that the battery replacement would be covered under warranty.

 

i hope so, i think the warranty is 3/36. don't let them see the dash cam

 

@bisco Unfortunately that is (semi) permanently installed...would be a huge pain in the butt to remove being a 2 channel dash cam... Not just cabling but that stubborn 3M VHB adhesive.

...but here's my argument. My 2016 Prius never once had a dead battery due to the dash cam or any other accessories that I might have left in. I assume that both the plug-in and regular Prius use the same or comparable 12 V batteries in terms of rated capacity. Plus the battery would have been older in the 2016 at 2 years. Plus the Prime gets a small "boost" while plugged in charging.

Unless there are other "vampires" in the Prime there really shouldn't be any differences when it comes to the 12 V battery or how it is charged, they're both 4th gen Prii.

 

i hope they cover it, let us know. all the best!

 

The dealer says my 12 v is down to 40 percent of its original capacity on my 2017 Prius prime. . As far as I recall , the 12 v battery from Toyota has no warranty coverage at all. But iirc on my gen 2 , the dealer replaced it as a favor once.

I took my car in yesterday because the hybrid system water pump failed and the service advisor said the 12v wasn’t covered.

make sure you get that platinum warranty !!

my car died and it spit out p148f00 p261a13 p319300 and cia63. The check engine light came on and it broke down a mile or so from the
Store and wouldn’t start. The repair would of costed $1700 for the parts and 7.5 hours of labor !

those water pumps only have. 60,000 warranty

there is so many websites about that yellow top , I have no idea where to get a Prius prime 12 replacement, I’ll need one soon

 

For battery info, from
@Elektroingenieur

Gen 4 12 Volt battery. | Page 2 | PriusChat

 

Don't buy a yellow top, it won't fit in a Prime.



Rob43

 

I made a note of his information and stored the link for future reference. Good stuff!! Thanks, @Elektroingenieur.
Gen 4 12 Volt battery. | Page 4 | PriusChat

 

So, my 2018 Prime's battery died while I was waiting for an hour and a half in a parking lot for curbside pickup. There car had sat for a few days before this short trip. I had Carista plugged in and I ran the car in accessory mode for about 45 mins to listen to music. Oops.

I replaced the battery due to lack of time to investigate and I also didn't want to risk it dying again later this winter.

New OEM battery I got from Toyota is rated at 445 CCA and 75 R/C which I think it's equivalent to about 31 Ah.

This is different than original battery with 295 CCA and 45 Ah.

Thoughts? Did I get an inferior battery???
Pictures of old and new battery attached.

 

I googled converting r/c to ah, with mixed results. The following seems plausible, saying just divide r/c by 2 to get ah, but don’t count on it; there’s no hard-and-fast correlation.

Battery Confusion - Amp Hours vs. Reserve Capacity | SailNet Community

I’d suspect if Toyota’s ok’d this battery it’ll be comparable to original.

 

Yeah, I saw that article as well... Reserve Capacity vs Amp Hours, too many unknowns to calculate accurately.

Assuming the battery's labeled 75 R/C is 75 minutes at 25 amps ( see Battery Reserve Minutes | BoatUS) I esitmated the amp hours at 31 Ah as follows: (75/60 ) [hours] * 25 [amps] = 31.25 Ah

With the new battery, I get more CCA but the way I understand it that's not important with the prime since it doesn't have a starter motor. I'm a bit worried about the "apparent" reduction in capacity though... If the 31 Ah vs 45 Ah comparison is accurate, this new battery would have about 30% less capacity...