12 volt battery failing to start the car

Louis: That was an incredibly detailed very useful explanation. I, for one, really appreciate the time you took to write this. I have already sent it to my family members who have 2023's.

 

Louis: That was an incredibly detailed very useful explanation. I, for one, really appreciate the time you took to write this. I have already sent it to my family members who have 2023's.

 

Well done, Kudos to the thread opener!
I have a 2023 here in Europe. Not from many days. Changed a setting somewhere and now the radio continues to play (I don't know for how much time, though), even after I pushed the STOP button. Only when I open driver's door, the radio shuts off. So IF you close the connection to the HV battery (pushing the STOP button) and wait in the car listening to the radio, you are draining the 12 volt battery!
Regards
Alessandro

 

Thank you for taking time to write this great explanation. My cars battery died while the tint guy was applying the tint and ppf. I haven’t driven it at all. Just from dealer to the garage. So it didn’t have juice. Had to jump it. And looks like the battery got charged either by me starting the car, even though engine itself never started. Or by plugging the charger in. So if I leave the car and don’t drive it for about 10-15 days, I don’t need trickle charger if the car is plugged in? Since that will charge the 12V battery? And the HV battery will charge the 12V battery when car is driven, even if engine doesn’t start? My daily commute is under 40 miles typically. Just trying to understand if 12V battery will be ok with me by just plugging the charger and driving 85% of the time using HV battery and not running the engine. Thanks again!

 

Keep in mind the charger will stop charging the hybrid battery once it reaches 100% and then turn off. So it seems (unless I'm corrected) that the charger will not continue to trickle charge the 12V battery. IMO, hybrids (as well as all autos) are meant to be driven regularly, not purchased and then driven only once every two weeks.

 

modern electronics put a lot of drain on the batteries when cars are off.

prius suffers especially because of the battery size. we've never had a problem with our camry's

 

thank you for response! Yeah I just didn’t want to drive it until PPF and tint is done as well as I’m blacking out wheels and emblems. But mainly didn’t want to drive it without applying PPF first. So because of it battery died. And also my carpool stickers have not arrived yet. So I have been driving my other car which has the stickers on.

 

That’s a problem. We’re infrequent drivers, and it struck me as absurd that the car needs to be “walked”, near daily, to avoid a dead 12 volt.

Being garage parked and having 120 volt outlets, the solution was obvious, but for for condo and street parkers it’s a quandary.

Maybe one of the automakers will take a break from styling exercises and devote some attention to this, say come up with something that’ll store all the volatile memories and isolate the battery when the car’s off.

 

Well, that is a great example of the real problem. Some guy gives his opinion, based on nothing, then you take it as fact and pass it on with more opinion, based n the first opinion that was not true, and now we have a much traveled myth. I don’t use my Prius Prime every day, or anywhere near it. My wife doesn’t use her Rav4 Prime every day, or anywhere near that. I didn’t use my Venza hybrid that I had before the Prius every day or anywhere near that. I could go on, but you get the idea. Sometimes either one of them or both of them will sit in the garage for more than week. We have never once had a starting problem with them or with any of the many hybrids that we have had. Stop passing on baseless opinion because you just want to find something to complain about.

 

Nope, based on personal experience.

 

Is that your opinion?

 

Are you seriously asking that?

 

If you're questioning if the issue is real all you have to do is search.

A search here, over the entire PriusChat forum, for "12v dead" yields the following 7 pages with 122 results:

Search Results for Query: 12v dead | PriusChat

A similar search on another major Toyota forum, limited to their Hybrid section, yields the following 24 pages with 468 results:

Search results for query: 12v dead | Toyota Nation Forum

I suspect it's not a pervasive issue - if it was there would probably be class action lawsuits - but it doesn't seem to be "a myth" either.

I'm new to Toyota and hybrids. While I haven't had a problem with starting I have been concerned.

I installed a voltmeter in the lighter / accessory outlet to monitor the situation. I check it in ACC mode by pushing the Start button once without a foot on the brake pedal. I've seen readings as low as 11.6v which, according to a chart posted elsewhere, indicates that the battery is only 20% charged. For some reason it increases a couple of 10ths after a few seconds. The car has always started though. After starting the voltage jumps to between 13.9v and 14.2v, which indicates that the battery is being recharged. After driving a while it will drop to ~12.8v.

I suspected that the battery may not have been fully charged when I got the car (about a month ago) so I put a 2A trickle charger on it and it took a total of ~11 hours to bring it up to full charge.

It's a hassle to run an extension cord out to the car so I picked up a 20w solar charger whose maximum output is 1.1A. It's very thin and light so I've got it mounted on the cargo cover using binder clips. Toyota says you shouldn't charge the battery while the Hybrid system is on so I only have it connected when I'm parked somewhere for a while.

I just started doing this. I plan to try it both with and without the solar and I'll be keeping track of the results. Hopefully the solar will either offset any parasitic drain on the battery or not be needed at all.

 

Yes I did seriously ask that. Aside from simply criticizing what others say, do you have any other information or thoughts that would be constructive to the discussion?

 

as I said before, I have had “personal experience” of my own. 1. I have now owned, at one time or another, five hybrids, two are plug in hybrids. I have never had a problem starting any of them. 2. I have several friends (yeah, I do) that have hybrids and plug in hybrids (I am very positive toward PHEV’s). None have had a problem starting their cars. 3. I went to the three Toyota dealers in my area. Two said they see this problem rarely, but do see it. They said it is almost always attributable to an accidental draw on the battery and is usually user error. They mostly see it when the owners simply forget to turn the car off, which happens mostly with new owners who don’t realize that the car is still on (and walk away leaving the car on) because there is no engine running. The second cause is accessories wired in that draw down the battery over time. One noted a draw on the battery that was due to a faulty part not turning off when it should. In that case, you have to realize that this is not a Toyota Prius Prime problem, it happens to literally every make and model of car.

There seems to be a hysteria over this, or for that matter, several other issues discussed here. For instance, here we have a guy that admits that he has never had a problem starting his car……ever. But………due to these threads he buys a voltmeter and installs it into the lighter socket to check voltage every time he starts his car. And the beat goes on. I realize that you all think that I am being too critical. Maybe. I think that a lot of you (see prior example) are simply being too paranoid and/or just need something to sit at your keyboards and waft about negatively. Honestly, I am not like this normally. I came here to see what people were saying about their primes after buying mine. But sometimes it is just ridiculous as far as what you all complain about. It is literally like a bunch of old men sitting around complaining about nothing. But if that is what floats your boat, then I suppose it is no big deal and I will just go into read only mode and visit less often, no hard feelings here. Enjoy.

 

as I said before, I have had “personal experience” of my own. 1. I have now owned, at one time or another, five hybrids, two are plug in hybrids. I have never had a problem starting any of them. 2. I have several friends (yeah, I do) that have hybrids and plug in hybrids (I am very positive toward PHEV’s). None have had a problem starting their cars. 3. I went to the three Toyota dealers in my area. Two said they see this problem rarely, but do see it. They said it is almost always attributable to an accidental draw on the battery and is usually user error. They mostly see it when the owners simply forget to turn the car off, which happens mostly with new owners who don’t realize that the car is still on (and walk away leaving the car on) because there is no engine running. The second cause is accessories wired in that draw down the battery over time. One noted a draw on the battery that was due to a faulty part not turning off when it should. In that case, you have to realize that this is not a Toyota Prius Prime problem, it happens to literally every make and model of car.

There seems to be a hysteria over this, or for that matter, several other issues discussed here. For instance, here we have a guy that admits that he has never had a problem starting his car……ever. But………due to these threads he buys a voltmeter and installs it into the lighter socket to check voltage every time he starts his car. And the beat goes on. I realize that you all think that I am being too critical. Maybe. I think that a lot of you (see prior example) are simply being too paranoid and/or just need something to sit at your keyboards and waft about negatively. Honestly, I am not like this normally. I came here to see what people were saying about their primes after buying mine. But sometimes it is just ridiculous as far as what you all complain about. It is literally like a bunch of old men sitting around complaining about nothing. But if that is what floats your boat, then I suppose it is no big deal and I will just go into read only mode and visit less often, no hard feelings here. Enjoy.

 

Hey no worries! No hard feelings here either.

 

the problem is the health of the 12 volt. as it ages, it discharges more rapidly when a car is off (because there is a constant drain)
for this reason, no two experiences are the same, and no one knows how long there car can sit before it won't start, but it can't sit forever.
and when it is driven, longer trips gives it more chance to recharge than shorter

 

Yes, I installed a voltmeter and I'm glad I did. Otherwise I would not have known that the battery was only 20% to 30% charged.

This is after driving the car, typically, every other day or every 3rd day at least. I'm not going a week or more without driving. So I've got to wonder how much lower the charge would have dropped if I didn't drive it for a week or so.

Now that I've brought the battery up to full charge I'm just trying to get a handle on how serious the issue might be. Based on actual measurements rather than on purely anecdotal accounts.

I agree that @Louis19 's comment about "a sudden rash of 12v battery failing to start the car" might be an exaggeration - most Gen 5 owners don't seem to be having issues - but I don't think your claim that it's all "a myth" is accurate either.

That's based on the search results I posted, which you seem to ignore just because you and your friends haven't had a problem.

Otherwise, his post is very informative. As he points out, it seems that a Prime or other brand plug-in would be far less likely to have a problem since every time it's plugged in for recharging the traction battery the 12v also gets recharged to some degree. Presumably, it also gets recharged while driving. The regular hybrid only recharges the 12v while the car is running. Over time I expect I'll learn if that is sufficient to keep the 12v fully charged when the car isn't driven daily or for long distances. He claims that it should only be a problem if the car isn't driven for "a few weeks".

I find it hard to believe that any significant number of owners simply leave the car running. Would this even cause a problem? According to the manual the car will automatically shut off after a while and during the time it's running it should be recharging the 12v battery since no energy is being expended driving the car. When the traction battery gets low the ICE kicks on and recharges both the traction battery and the 12v.

I have no added accessories and the LE may even drain less energy that other trims since it doesn't have navigation, etc. The only accessory I use is the radio and I do usually use the DRLs. I do wonder how much the Toyota app, which tracks your car using GPS, contributes to the voltage drain. I installed it reluctantly, mostly for the "Roadside Assistance" due to the lack of a spare tire. I later found out that their flat tire service is restricted to "installing your inflated spare", which doesn't exist so it's totally useless.

I'm also a bit skeptical that the dealer will give you the whole story. I read through several threads from the search results and a couple, posted a few years ago, indicated that Toyota has done software updates in an effort to solve the problem. So it seems it's not totally due to driver error.

I certainly have no hard feelings toward you, either. But your claim that this is "a myth" is not accurate or helpful, IMO.

 

correct, leaving the car running is fine until it runs out of gas.