In READY mode, with the ICE start to charge the 12v battery?

Owning this type of vehicle means going green, that is certainly not keeping with the theme.

 

I've seen several comments from long-term owners who say the 12V usually lasts 3-5 yrs. What would you suggest? I certainly don't want to get stuck somewhere with a dead battery. And I don't want to keep jumping a battery. Being green is fine, but my safety (and having a reliable car) comes first.

In previous vehicles, I never got more than 3 yrs out of a battery. If the Prius is different, I'm all ears. Thanks.

 

I got 8.5 years out of our 2010 before I swapped it out January 1 of this year.

Get a multimeter from harbor freight and use it to your advantage .

I check that along with oil level every Saturday and takes a total of less than 5 minutes.

 

That would be great.

 

The voltage on my 2012 battery is dipping down to 11.9 if I do not drive for a day, I will replace it when I next see the dealership. Without that slow starting sound (in a Prius the 12 battery does not start the engine, just the computers) most owners do not notice when to change the battery, leading to jump starts.

 

Does checking 12v battery voltage on prius has to be done under hood with a meter, or is there any scan tool that can read 12 v battery condition off from OBDII link?

 

You can get it off the obd2 port, but the Prius won’t be stone cold to get what the car is at rest.

While a load test with a multimeter is more telling, the at rest level is worth something .

 

Oh, I see what you mean. Do I have to disconnect 12 v battery to test it or can I just check voltage while connected?

 

Not sure. There is a 12V in the OBDII port that's always hot on my PiP because my reader lights the LED when I plug it in with the car off. But I can't get any info out of it.

However, if you're just wanting to check the voltage, under the hood with a meter is far and away the easier and quicker method. Also, accessing the OBDII port without opening the driver's door and activating the brake accumulator pump would be more awkward than reaching across and popping the hood release.

 

No. Just don't do anything to drain the 12V battery before testing.

 

No need to disconnect.

I changed ours out when it got to 12.3 volts as it was reading 12.6 for the longest time.

My role changed at my job requiring me to be in two places sometimes rather quickly to attend meetings which led to very short trips in our Prius (less than 0.5 miles). This was 6 months prior to the battery showing lower voltage.

Pretty sure that’s what made it go on it’s last legs. All sorted now though and still check on every Saturday.

 

Thanks @jerrymildred and @Raytheeagle . Living in cold climate all my life, I have experienced many times weak or dead battery that won't crank up the engine in dead of cold winter, and that has been always tell tale sign I needed a new battery. As I stated in post #16, I didn't own my previous Prius long enough to experience any of battery issues. With Honda Civic Hybrid, even though 12v battery is not used for starting the engine under normal condition, I experienced dead 12 v battery one cold winter morning. I charged the battery and it started right up, but I knew then it was time to replace the 9 years old OEM battery. From what I learned so far, it sound like Prius seems to behave differently.

 

With a mulimeter or a Scangauge you can test the 12V battery "under load" by connecting the meter or pressing the "on" button on the Scangauge (button with a circle around it) and turning on the headlamps. They offer a pretty good load for the Prius. Of course on the Scangauge you have to have it in the mode displaying four readings with one of them being the battery voltage. You don't need to turn on the car to have the Scangauge on, though it won't stay on very long, but long enough to see the reading. I would connect the mulimeter to the "boost point" under the hood in the fuse box on the left side of the vehicle, just because it's easier to get to than the battery under the hatch floor.

Of course the next question will be "at what voltage should I consider replacing the 12V battery?" I would be concerned if it was below 11V, as my Scangauge often reads 11.5V, or at least used to. The voltage -should- be around 12 to 12.5V after the car sits overnight. Below 11V means "change the battery NOW!"

 

After reading these posts, I will be more pro-active about the health of the 12 volt battery. I recently bought a plug in "splitter" so I could have 2 ports under the dash for charging phones and tablets. It came with a digital readout that comes on when you turn the car "on". it generally reads about 14.5 volts. That of course is with the HV battery giving it additional juice at rest but in "ready" mode. So, I too, wondered about the status of the 12 volt at "rest" with no help from big brother battery. I also do some camping, so we bought a Koolatron thermo electric cooler so we would not have to keep buying ice. I run it off of the 110/12 volt adapter before heading to the campground, then on the way I plug it into a dedicated, fused 12 volt outlet I wired directly to the battery. It has a power outlet similar to the one under the dash. We might stop for 30 minutes or so with the cooler running, but with the car shut off. it draws 4 amps and so far it has not drained the battery down much at all for those brief stops. I just realized that I have a digital, plug-in voltage meter that used to have on my Gold Wing and no longer was using. I went out and plugged it in the outlet at the back of the car (off the battery) and it reads 12.5 volts. So, without much hassle I can get a true, at rest reading of the battery any time I want to, and not get the multi meter out of the lower storage area. So...thanks for these reminders about the little "lawn-mower" sized battery out back tucked away and out of sight...out of mind until your car won't start!

 

That cooler sounds pretty handy. But I would caution against having it plugged into something hot with the car off. Just a matter of time before you have a 12V that's too low to wake up the car. Then you're looking for a jump and praying like mad that you don't have a brain fart and hook it up backwards.

 

The last pocket-sized lithium jump pack I bought came with cables that detect reversed polarity, and won't close the circuit.

-Chap

 

My lithium ion jump pack detects reversed polarity too, but only from the "boost" port. On the Prius I don't think you need to use that port. I would be tempted to use the 12V supply one, as the Prius current draw is so low. But it doesn't have polarity protection. I hesitate to use the "boost" port as it requires an additional step of "activation" and then another of "deactivation". It will start a large V8 it claims though, but only a few times and it's done. Kaput! I've used it to power my Amateur radio a few times in the field (KX3). From the 12V supply port of course. Mine is the larger one, bigger than a video cassette (remember those?).
Never had to use it to boost a car, YET! (I just had to say that.)

 

All this talk about reverse polarity on jump starts makes me think Prius owners are kindergarten aged children. I have owned cars since 1980 and have used jumps more times than I can remember, but I have never ever had a reverse polarity episode. I really don't thinl it's that complicated. Red lead to positive, black lead to negative. What am I missing?

 

AMEN!

 

I agree, but it seems to happen to others.