I've done it before, walked off with my headlights on and drained the battery. I know the III has an auto off for the headlights, but can the dome lights (or something else) be left on and drain the battery? Since this is a smaller battery, is it in issue to sit in the car for an hour (waiting for someone for instance) listening to the CD? Could I impair the battery doing this? Am I correct in assuming that the big battery is used only for running the car and is not involved in starting the car or running auxiliary devices? In other words, it's not a backup in certain situations to the small battery?
There are things you can do to drain the 12v battery, but not the HV (without doing some major, extreme and intentional damage). If you exit the car from the passenger side with the headlights on for some reason (like one of our estemed moderators is wont to do on occasion) the headlights won't auto-off. If the hatch doesn't close all the way the hatch light can stay lit and eventually drain it (I turned mine off permanantly). Prolonged sitting will do it too...usually takes 2-3 weeks minimum.
The HV (big) battery is what starts the engine but it connects to the rest of the car through a relay. The aux (small) battery must have enough power left in it to close that relay when you press the power button (with your foot on the brake). If you are going to set in the car with things turned on, lights, audio system, even the air conditioning you can leave the car powered up and everything will run off of the big battery and when it gets low the engine will start and charge it up again. When the HV battery is on line (car powered up) it runs everything and charges up the aux battery as well.
I've wondered the same thing too. I suspect even though the 12 volt is smaller than in a conventional car, having the radio on for a couple hours won't touch the 12 volt as the radio draws a relatively low amount of juice. I would also expect the dome lights being on for an hour while doing a thorough cleaning of the inside also shouldn't be a problem. Is that a safe bet?
The traction battery (big high-voltage battery) runs the Hybrid Synergy Drive (HSD: Engine+2 electric motors) and the A/C compressor. Everything else runs on the 12V circuit, which is feeded from the small 12V battery and recharged from the high-voltage circuit through the a DC-DC converter in the inverter (so the traction battery recharges the 12V battery when the car is on). The traction battery then recharges from the HSD.
Ok, so now I know the aux battery is required to start the engine and there are things I could do to drain like leaving a door ajar. I don't think I'll have to much trouble remembering to get out on the drivers side. It looks like if I'm sitting in the car waiting, the thing to do is have the HV battery online. I am surprised that 2-3 weeks of sitting can drain the 12v aux battery.
Last night I left my headlights on and came inside. The Prius turned them off automatically after ~15-30 seconds. Came out this morning, car was fine. Makes me just want to always leave my headlights on. <3 Prius
I worried about my battery dying last weekend. I was at the Newport Folk Festival and after it was over, there were thousands of cars waiting to exit the parking lots. I sat there and watched my battery go down to 2 bars. I wound up turning the car off as we sat in line to exit for over an hour. Should I have been worried?
No need to worry, the battery never gets below the level required to start the engine. The engine will start as necessary to maintain the High Voltage battery. You could have set for days as long as you had enough gas.....
I was so excited the night I picked up my car, so when I got home I turned on the dome light to check it out and got out and forgot to turn it off. Didn't see it until the next morning. The car did start but I am wondering how badly that affected the 12V battery? And does this mean it's going to need replaced soon? Sorry if these are silly questions, but I'm a "newbie" with the prius.
Don't worry. If the car started fine in the morning, the battery had enough juice (and wasn't discharged too much). It's never good to run down a lead acid battery too much, but I don't think you did any damage to the battery by leaving the dome light on all night. I wouldn't do it often, though... ;-)
Always lock the car when parking it. If any of several battery-draining conditions exist (door or hatch ajar, vanity light on, car not OFF) it will give a long warning beep. Don't leave it in ACC or IG-ON or in Neutral for any length of time, or you risk draining one or both batteries.
I'm sure you're right, but I thought the owner's manual said that interior lights would go out after 15-20 minutes. (can't cite page, I don't have my manual with me).
No, you won't need to replace it any sooner than if you didn't leave the light on. I did this several times in my 2001 Prius and it is almost 9 years old and I still have not replaced the original 12v battery. i.e. it has lasted longer than any 12v battery in any car I ever owned. After owning my 2010 for only a month I went on a 2 week vacation. The car started perfectly fine when I returned. It would take much longer than 2-3 weeks to drain the 12v battery, IMO. And my 2004 was also just sitting for 2 weeks (minus a couple of hours) and it started perfectly fine. 3PriusMike
Thanks for all the replies -- if the manual does state that than it didn't hold true for mine. It was definitely on when I went out the next day. It was the drivers side light that you push -- map light maybe? Not the main light when you open the door-- maybe that one will go off.
Most Dome lights have a three position switch, 1) Door Position-light comes on when door is opened and Off when closed, 2) Off-self explanitory and 3) ON-this position turns the light ON indefinately! If the switch is in the Door position and a door is ajar, it will turn off in (I think) 20 minutes, if left in the ON position it will NOT turn off. David (aka Blind Guy)
