This morning I ran a 12v battery test on my 08' Prius by pressing the display button and switching the headlights on and off 3x. While on here I had only pressed the power button once (w/o brake) and i got a reading of 12.2V. Next i turned on my headlights and it went down to 11.5V. After i pressed the power button one more time w/ headlights on and it went to 11.2V. Lastly i powered my Prius on w/ the headlights and got a reading of 13.8V. My question is should I be getting a replacement 12V battery or is it still good? I am not really savvy at auto knowledge. I have been looking up this information but mosts videos/posts people have their battery dip below 11V in the ranges of 9-11. Another question I have is since its above 12V when fully powered does that mean that it is working as it should and not be causing warning lights? My Prius currently has the BRAKE, ABS, AND VSC lights on since yesterday morning. I drove it around my home for about 2 miles and it seems to drive and sound like normal as well. 3/8/13 -found this date on the toyota website and I'm guessing this was when last battery was changed at 89k miles i have 129k almost about now. SCAN TEST AND DIAG. HAS BAD AUXILLARY BATTERY - PLEASE SEE LINE 52 FOR REPLACE, REPLACED AUXILLARY BATTERY AND CLEARED CODES, REPLACED SEPINTINE BELT, PERFORMED COU RECALL - REPLACED INVERTER WATERPUMP AND BLLED SYSTEM, PERFORMED INSPECTION, STEERING EXTENSION SHAFT OK, REPLACED 3 BOLT could the 12v battery be causing all this?
You should charge the 12v battery. I don't think that's the cause of the lights. You might want to get the codes read so you won't have to guess at the problem.....but definitely charge the 12v
Toyota themselves has a replacement battery with a 84 month prorated warranty, that may be the life of the car at this point. (if it wears out and you are still driving it, great!) But any AGM battery with JIS posts is fine, ideally size S46B24R.
taking to the dealer for a diagnostic fee in a couple hours to see what the real problem is. thank you for the replies
YOUR 12 V battery looks a little low, but not bad. it could use a slow trickle charge overnight to bring it back up to full charge. i have checked my battery several times after fully charging, and readings thru the display always show less than what i see with my voltage meter directly at the battery. mine usually reads around 12.3 unless its fresh off the charger then its 12.5. at the battery i get 12.8 to 13.0. this is an optima battery. i estimate when the computers are on to display the voltage its a a .5 V drop from actual battery voltage. your problem is probably not battery related, just a bad sensor or switch
