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

Running the gas engine has nothing to do with charging the battery. The charging when driving is done by the traction battery, so EV mode is fine for this. However, a 15 minute drive will probably not be sufficient to bring the battery up to a full charge, which is what you need to do. I would recommend getting a charger.

 

What's said above. Obviously, your 12v has hit the bottom of SoC and 15 min of onboard charging is not going to bring it back. Even with a smart charger which you are somehow refusing to buy, it may not be brought back to life. But at least if you do hook it up to a smart charger, it has a chance to rejuvenate for a while and it may last 6 days provided you keep it trickle charged on a battery maintainer mode or charge up your traction battery and turn on your car to READY for ~1hour, once a week (you do not have to drive the car). I have tested the charging on my 12v, and found plug-in has almost no charging capability. It only maintains the 12V battery but not replenish the SoC. With my almost brand new 12v battery in 2020 PRIME, ~1hr of drive (or just READY) mode with plenty of SoC in the traction battery, 12v SoC can be replenished from 12.4 (60%) to 12.7 (100%). However, repeated weekly ~1hr drive slowly brings this SoC down, so first week 12.7v, second week 12.68v, third week 12.63v... and so on. Thus even with this routine, it is desirable to put the 12v on a smart charger once in a while to charge up and put the battery on maintainer mode if you can, until you drive more often.

 

Buy a new ~$150 dollar battery....and then buy either a ~$20 solar panel or a ~$25 trickle/maintenance charger.


Rob43

 

take it to an auto parts store for a free charge and load test. if it passes, you should be fine driving it once a week. if not, and you don't want to buy a maintainer, you'll need a new battery, but leave the 12v neg disconnected until that emergency comes along.

 

i would not disconnect the 12 volt negative on a Prime (for weeks to prevent discharge) because that would prevent the car from turning on the traction battery fan and possibly hurt the traction battery.

 

What would that do to the balance of the battery cells after an hour or two of radio listening?

It is, according to Toyota's apparent design goals. They could have put in all sorts of special features to increase the cost and make it even more intimidating to the broader customer base, but they wanted to make it an easy and attractive transition to more than just enthusiasts like us. They could have really gone all out adding that feature and lots of others, but I doubt they would have sold very many cars that way. Too expensive and too different. (BTW, as an unrelated forum tip, it's easier to read your response to a quote if you put that response outside the quote. It happens to lots of people new to the forum. )

In fact, I think it would have been smarter to not even have an ACC mode. I only use it on rare occasions when I want to roll the windows up or down and don't feel like sticking my foot inside the car to press the brake pedal.

 

the car cannot turn on the traction battery unless you make it ready.

you can't hurt the traction battery.

how would you change the battery without disconnecting the old one?

 

What do you think is happening when the Prime is off and a fan at the rear of the car is going? The only thing I think of is that the cooling fan for the traction battery is on for some traction battery maintenance purpose. The fan cooling of the traction battery can work whether the traction battery is on or off. Temporary removing of 12 volt negative is not going to affect this, but using a 12 volt negative disconnect to protect a 12 volt battery discharge over weeks would.

 

Yeah, I agree. I don't know why they even bothered to keep the ACC and ON mode on this vehicle. Knowing the short life of 12v outside of READY mode, the manual mentions repeated cautions not to use various functions on the vehicle without the hybrid system on (READY MODE). I counted, there is a total of 35 incidents of such warning listed on the manual. The simplest solution would be to not to offer those choices.

 

Under what conditions do you think the traction battery would become hot enough to trigger the fan.......while just sitting there idle ??
Hint: Unless maybe it is parked out in the middle of a desert where the temp is 140 F......it won't.

 

Many times the Prime sits in my garage while off and the fan comes on. I hear it in rear of car. Usually in summer.

 

Does that happen while the car is plugged in and actively being charged, or just parked not plugged? In my local, I have not yet seen my car uses the traction battery cooling feature, but as I understand it that feature is only used when traction battery needs to be charged and the battery temp is too high.

 

Would these be true, or no:

1. If the car is off, the hybrid battery fan only runs when the hybrid battery is being charged.
2. That fan is not drawing down the 12 volt battery.

 

Thanks for the quote tip. I thought I had messed that up.

It seems to me that with a relatively simple firmware change, Accessory mode could simply be Ready mode without the capability of driving. Allow everything to work but the gear selector.

 

the fan you hear is the pollution test system. all prius have it. you can find it in the manual. it's not needed if the car is not being used

 

That's what manual indicates, as far as the "Traction Battery Cooler" function is concerned.

 

I searched for the "pollution test" or just "pollution" in the manual. No hit. Is it a different term Toyota uses?

 

Maybe @bisco is thinking about the odd noises the emanate from 3rd gen Prius, maybe from the carbon cannister or gas evap stuff, some time after shut down?

 

In the manual, there are a few mentionings of the "fan" operating sounds, but all seem to be during charging or READY mode thus the traction battery rather than 12v is used to power the fan.

 

Really ?
After it has been OFF for how long ?
And while it is NOT plugged in ??