Prius Prime - 12V Charging System

@Rob43 has a thread for that. i think there is more load on the battery when the car is off. so if you don't drive often enough, it keeps going down. true of a ll prius and cars in general, but prime drops faster than anything we've seen to date.

if you drive 20 miles a day, it should stay at 12.7v, anything less and at some point, it will drop a bit each day. depends on how often you drive, and how far.

a maintainer is a good idea

 

This statement should make 12v battery voltage A OK, so if you're still see a somewhat regular decline in 12v performance/capacity; I'd blame that on the stereo & amp.

************************************************

Either one of three scenarios is taking place: (I'm betting on #3)

1) Stereo & Amp have now gone slightly defective, but still work.

2) Stereo & Amp have a larger parasitic 12v drain than the Prime can deal with when off.

3) Everything is working correctly, but the Stereo & Amp simply use up more 12v amperage while playing than the Prime charging system is giving back. Then while parked the Prime experiences its normal parasitic 12v drain that every Prime owner deals with.

IMO: A 12v battery monitor and 12v battery trickle charger are needed.


Rob43

 

You could always install a flexible ~100 watt 12v solar panel on your roof....



Rob43

 

It’s a bidirectional DC-DC converter, with voltage ranges and power-handling capacity suitable for automotive applications; the second and third pages of the User Manual (PDF) linked from the product page give specifications and a block diagram. It also seems to be out of stock.

It’s certainly not used on any Prius car. I think the seller just means that it’s a generic part; some other sources say it was used in the Coda electric vehicle.

 

My two cents...

I religiously plug in my 17 prime and try to stay within the EV range. I’ve had the dead 12v way too often. The prime only charges the 12v little battery when the gas engine is running. So, if I’ve driven 25 miles in EV to a store and my kids wanna stay in and listen to the radio for 10 minutes, that will drain the 12v too low to start the car. Same if I need to use an air compressor to inflate a ball or tire... it’ll drain the 12v so much that the car won’t start. I carry a portable jump start pack, and will buy a new 12v battery one of these days. But yeah, the rule of thumb is that the 12v battery only charges with the gas engine running.

 

Not true. The Prime charges the 12V battery anytime it's in the READY, not just if the engine is running.

Obviously, if it's in READY mode, it can be driven, so depending on the age of the kids it could be dangerous. Note, it would be no different than leaving the key in an ICE car in ACC mode. It could be started and driven, just as dangerous.

 

This isn't because the engine was off. It's because the car was in accessory or ignition mode rather than ready. I often drive as much as 200 miles in EV only without running the ICE. I have over 2,800 miles on this tank of gas so far. Others here go for about a year without running it. No dead batteries.

As @Mark57 already said, the car charges the 12V any time it's in READY mode. Whether the engine is running or not. Otherwise, it would not be a viable means of transportation for normal people.

 

I have a question re the 'security indicator' light on the dashboard (red car with a superimposed lock).
I bought my 2017 prime plus this past December and have put about 2000 miles on it as of today. Due to covid I am furloughed right now, and my guess is my job (travel industry) may be pretty much done, and will probably end up just retiring at the end if the day. Since I won't be driving to work any longer I will end up using this car for trips around town doing errands from now on.

I had my 12v battery replaced on Wednesday, since it did die. Luckily it has enough juice to give my a warning I'd low 12v battery before giving up the ghost on .Monday. (Car has a bit over 45000 mile on it).

I did an errand yesterday and the dashboard indicator showed up when I turned the car off. It kept blinking and is freaking me out. I went out about 1/2 hour latervto check it and it was still blinking. I did check today and it looks like it is out.

I really don't understand this car which is a problem for me since I don't know if that light should be there or not. I don't want it to drain my new battery!

Re the dashboard light, I never noticed it on before yesterday so I am not sure if this is an issue.

I did some reading and discovered the accessory mode,etc. the car description says it has "eng immobilizer " included under optional equipment.

Is there a way to disable that, or keep it out of accessory mode, or some other way to stop that flashing light, or is it just part of the system and won't do any harm with my battery?

Also, is anyone has a link to a good, encompassing tutorial about this car, let me know.

Hope this isn't too much info, and thinks in advance for any help, suggestions.

 

Toyota’s 65-page Quick Reference Guide (PDF) explains many of the car’s features, but the Owner’s Manual (PDF) is the comprehensive reference.

In the Owner’s Manual, the immobilizer system is covered on pages 75–76, where Toyota writes, “The indicator light flashes after the power switch has been turned off to indicate that the system is operating.” A note on the next page warns, “Do not modify or remove the system.”

I’m not aware of a practical way to remove or disable the immobilizer system or security indicator, nor of a need to do so: the energy needed to flash the indicator is a very small part of the total parasitic current drawn from the auxiliary (12 volt) battery when the car is off.

 

Welcome to PC. Just stay tuned to this forum, you will learn everything you always wanted to learn about Prius and more.

As mentioned above, I don't think there is an option to disable the immobilizer system or security indicator, but again as mentioned that light blinking is not the reason you had a dead 12v battery in your car. Read Rob's comment #5 on this thread and his separate thread 12v Battery Is Discharging, Re-Charge Now ! | PriusChat.

Most parasitic draw on PRIME are not visible or obvious, and it is something that car does on its own. I checked SKS system but it was not the obvious offender. Is you are not keeping your car on ACC mode with radio blasting for a long time, or leaving the dome light all the time, although the car has a safety mechanism to turn off those light after a while on its own, the drain in the 12v battery is caused by many small internal functions of the car. Normal daily use will prevent the draining of the 12v battery, but the very short or less frequent drive seems to be not enough to charge the 12v in a long run. If you drove only 2000 miles in the last 9 months, that would make the 12v battery weak and kills already weaker battery. Since you already got a new 12v battery, now is a good time to get a battery charger/maintainer to keep the 12v charged while not being driven. I monitor the 12v battery voltage using a Bluetooth battery monitor and keep eye on the voltage drop over time while not being driven often enough. If the voltage drops down below 12.4v, either hook up the charger or take the car for a good long ride to replenish the 12v battery.

 

No one has addressed this yet. You "keep" it out of ACCESSORY mode by not putting it into ACCESSORY mode. You put it into the ACCESSORY mode from OFF by pressing the power button once without pressing the brake pedal. Press the power button again without the brake to put it in ON mode. When in either of those two modes, the display will declare the mode quite proudly.

If you leave it in ACC for more than 20 minutes or ON for more than an hour, the car will turn itself off. But by then the 12V battery could be drained pretty low.

The owner's manual is the best tutorial I know of.

 

Wow. Thank you all for these responses. I had a 1996 corolla which was on its last legs. I was considering a Prius and a business client suggested the prime over the regular Prius. (He has a prime). So it has been a big jump from that corolla to this new age.

I actually found this site during my research prior to purchasing the prime. The car did not come with an owner's manual but I was able to download it, even though it is not as convenient to reference. I did reference the manual about it before posting, and also found reference to that issue on this site from 2004 thread, but I wasn't sure if that info was currently applicable.

Somehow I got into accessory mode the other day for the very first time, as I always started the car the same way. the thing that freaked me out was that dashboard indicator light, thinking it was not supposed to be there. I had never seen it appear before. Maybe something changed when I used the fob key to get into the car after the battery died.

Early on I had a 'collision alert' appear while driving to work and I was not around anything. I took it in immediately to have them check it out. They said they 'found a code for steering angle sensor but the light went away', so now I am a bit skittish.

I now have lots of time to read the manual back to back. Thanks again for your insights and reassurance.

 

The Prime is a whole new world, even coming from another Prius. Mine didn't come with a printed manual either. I found one for $10 and bought it just so I'd have a complete car, but I've never opened the printed one. It's just too easy to find stuff in the pdf file using the search function in my computer. And then, too, I also have it on my phone and my tablet.

As for inadvertently putting it in ACC mode, that wouldn't have anything to do with using the fob. You just hit the power button without your foot on the brake.

There's a road near here that sometimes gives me a collision warning. It has a hard left turn and there's a great big high tension power pole on the outside of the curve that any car that misses the curve will hit. Basically, a death trap. The car panics almost every time. LOL!

The Prime does have some quirks, but I really love mine. Best car I've ever had.

 

Have a question on Prius Prime 2018, : the 12v battery went completely dead, as we have not been using it for few weeks.
Now, the AAA guy gave a jump start , and gave a bad news, that this 12v jump battery needs to be replaced.

It is has just 14,000 miles and just 4 years.

Does this 12v battery needs to be replaced with this usage and road life. Iam in Southern Calif, weather wise not that cold.

Do i have a case for any warranty support. Thanks for guidance.

 

See my postings about warranty coverage (expired, if it’s been more than three years to the day since the car was first sold); giving the battery you have a fair chance to recover through recharging, rather than replacing it out of hand; and if replacement is indeed necessary, the type of battery to install and where to buy one (equally applicable to Prius Prime cars).

 

Thanks Mr Elekroingenier: Appreciate sharing your thoughts. If i could, Does the charger that come with vehicle charges the 12v battery also, as part of the charging schedule at home ? If not, how does one re-charge just that 12v unit. Sorry , if it so simple questionJust making sure, before i go to the dealer, who may not be so inclined to provide that service. Thanks again.