Anyone else having 12V battery issues?

That is true of a battery which is not installed in a car like ours. Depending on when you test the battery, like if the trunk is open which turns on the dome light or if the ECUs of the car are still cycling since the car was running, or if the SKS is on and searching for a FOB, these and other things will cause normal and temporary drain. This will cause a lower reading at the battery. These things can be isolated with care such as timing of the testing or disconnecting the battery or running wires from the battery outside of the car and testing after the car has been sitting still for a while.

Some confusion is understandable. But the basic points are well made in the recent posts.

 

The problem may be that the +12V battery charger is not fully charging the battery. If the battery is good, the energy is either being drained while parked, or not enough energy is being stored.

PIPs don't have an alternator. Instead, they have a smart battery charger that is fed by the HV traction battery. That device determines the state of charge and decides when to charge the +12V battery.

After driving a while, where the battery should be fully charged, put on a load tester or other device to measure the state of charge. That will tell if the on board battery charger is working properly.

 

don't most of these loads turn off after 72 hours?

 

If I remember correctly the parasitic drain on the Gen II was 30-50 milliamps, it could be measured on the PIP also, because of the additional electronics it could be a bit more. I advocate keeping the car plugged as much as possible. I use the timer when charging at home 0300-0600, however I have a very good free charge daily option, so if I arrive at home with 5, 9 or 12 miles still on the car, thats all right with me. The perfect scenario is HV failure at 149000 miles and one month short of 10 years. I don't plan on being paranoid about overcharging to the point of UNDER charging. We still do not know of the details concerning the OP. It would be interesting to hear from him.

 

Rebooting never hurts, you'll lose a few memories, but they can be restored easily. Also there is a large fuse in or right around B+, at least there was on Gen II s it was 100Amp, more of a fusible link. You'll only have to check that IF, if there is still Nada at the instrument panel. Hope this helps.

 

Long period of time in this context generally means for months at a time. Not days or weeks.

 

12.6 volts at "rest" is considered to be fully charged for a 12V battery. so it sounds like you are fine.

The 12V battery is used to "boot" the computers, which in turn throw the High Voltage relays, which connects the HV traction battery to the car. At that point, the car is running everything via the HV traction battery. 12V items are powered through an inverter. The same inverter keeps the 12V battery charged, just like an alternator would in a regular car.

 

There is nothing magical about the 12V battery in the Prius, PiP or otherwise. Its just not as big as a what you find in a regular car since it doesn't have to crank over the motor. In my old 2005, I could have the car on in accessory mode (not in ready mode, and HV relays not thrown), headlights on, radio on, and the 12V battery would read about 12 volts. It might go as low as 11.7. A 12V battery is considered 'dead' at 10.8 volts.

 

I agree, it's silly to be fearful of overcharging, or to be fearful of anything.

 

In my 2005 GenII I left it for one month a year in a garage and returned to no problems. In that model, there was a button under the steering wheel to deactivate the automatic unlock feature; I always did that since the manual said to do so to conserve battery when left for over a week. I believe I read that the GenIII has this handled automatically since there is no button.

I have lithium electric bikes and I just disconnect the cell pack from the bike and charge every 2 months and store in the basement where it is not too cold or warm.

Since a full PIP charge is about 80% what would be the harm in charging it before going away for a month. I will have to read the manual and see what it says.

 

mine is in the garage from 02-19 thru 03-17. shut it down when ev ran out and ice fired. should be interesting to see how the 12v holds up, i never had any problem with my 04, it lasted 8 years. my 08 is still fine.

 

Manual says to deplete EV portion of the battery so that the car enters HV mode.

 

I'd like to know if it's considered normal for the auxiliary battery to run down after about 20 mins of having the accessories on. That's what happened to me, and it doesn't seem normal.

 

What do you mean run down? The car has an auto shutoff feature...I thought it was 15 min, but maybe it is 20 min. It shuts off and tells you it is to prevent the battery from going dead (or some such wording.) But it is just a timer and not checking the voltage. You can turn the ACC back on and it will go for another 15-20 min.

Mike

 

Nope. I was sitting in the car, listening to the radio, and after awhile the dash light got dim and it wouldn't start. I had to boost it to get it to start.

 

It's fairly common for the battery to discharge as it's not really big enough to do much more than start the computers when pushing the start button. You're asking for trouble sitting in a lot with the radio on for more than a couple of minutes without the car being in Ready mode.

 

I have played my radio with just the acc on and for a very long time and I have not had any problems with my battery going dead.

 

It

It's really not a good idea to do this in any car actually, but especially in the Prius. Car batteries are not deep discharge type batteries and repeated deep discharging of the especially small Prius battery will catch up to you with a failure much quicker than in a regular ICE car. The computers in the Prius need a certain voltage level to start and continued use in acc mode degrades the ability of the tiny battery to hold a charge along with a reduction in the voltage level when recharged. So the net result is reduction of the capacity more each time you listen to the radio in acc mode.

 

I did not know that. Thanks for the advice. I will not play my radio at all in the Acc mode anymore.