Not sure if this is coincidence or had something to do with it, but a couple weeks ago, ever since I had reset my oil change maintenance reminder on the display with the "PWR" and "Km/MPH" buttons pressed, the voltage on my Scangauge has dropped from 14.7 to 13.6. Since I got the car(or the Scangauge, rather), I've never seen the charge dip below 14.7-8 other than intermittently the past few months. These days it is staying consistently in the 13.6V range. The manual wasn't exactly clear on how to reset the reminder. At first I pressed the two buttons. All that happened was a continuous loud beeping sound. Then I tried the same but with the brake pedal pressed, and then the beeping went away and the reminder cleared. Did I alter the programming somehow with the first or second set of button presses so that the battery is not charging as well/efficiently? Everything else has not changed. If anything, maybe the weather has warmed up much more, but I can't see how that has much to do with the battery. I did use the AC once or twice the past few weeks, but again can't see how that could cause a big voltage drop like that. I remember someone else inquiring about a possible battery drain when they connected the relay of their HID lights to the big terminal post in the engine bay fuse box. That is how I wired my HIDs, but that has been well over 2 months. Or am I just being overly concerned and 13.6V is nothing to lose sleep over?
I'm not sure I would call it a primary battery. It's more of an auxiliary or accessory battery, or if you want to make it perfectly clear, the 12V battery. Air conditioning has nothing to do with the 12V battery. Air conditioning is powered from the HV battery, and when in this state, the 12V bus is also maintained by a DC to DC converter drawing power from the HV bus. Once in Ready, you can remove the 12V battery and the Prius will run just fine, including AC. In Ready, the 12V bus should be at somewhere around 13.8V. Tom
Not sure what you mean by the SG permanently connected. It's connected to that diagnostics port and has been there for a good 4-5 months ever since I got it. Now when I first get into the car and the SG powers up, it does initially show 14.7. Once I start driving, however, it quickly drops to 13.6 and stays there. I am practicing HM techniques now more often but can't see how that can cause the 12V battery charge to drop as a result of that.
But once again, does pressing the "PWR" and "Km/hr" buttons together without stepping on the brake pedal result in some function that causes reprogramming of some sort that may affect the battery charging?
No not that I am aware of, I have reset my oil change reminder 8 or 9 times and no problems. I watched my 12 Volt battery voltage for a while and it usually runs around 14.6 or so. But when the battery gets a full charge, and maybe especially during warm weather, I see it down to 13.5 or 13.6. I think when it sees a full charge it cuts the charging rate and the voltage drops to that level. Either that or there is a problem with the Voltage monitor and it just reads low from time to time. Need to check it with a meter when it reads 13.6 and see what it really is. Anyway I don't think you have a problem mine has been that way for 40K miles and I have not had a low 12V battery as far as I know.
This thread should answer your questions about varying voltage on the 12 volt circuit: http://priuschat.com/forums/gen-ii-...charging-12v-step-change-14-0-13-5-volts.html
Thanks for pointing out the thread. I didn't come across that when I was doing a search before. Definitely more reassured that this is normal car behavior now. Seems like a popular topic for the Gen 2. I'm surprised no Gen 3 owners have posted about this
