How to see if your 12v Auxiliary Battery is going bad

Video explains how to check if your battery is going bad in a 2004-2009 Toyota Prius. Please see my other video on how to change the 12V battery since it is a little more in depth than a normal 12v battery. Some dealers will charge you 300 bucks to change a Prius Battery. With a little knowledge you can do it for free plus the cost of the OEM battery.

Category:

Education

Tags:

• Battery
• check
• 12v
• Prius
• 2004
• 2005
• 2006
• 2007
• 2008
• 2009
• dead
• how
• to

[joesephwind]

Very helpful video you posted. I followed your steps and it's showing my 12v Prius battery @ correct levels. I already replaced the darn sucker @ $300 last year..Ran out of gas and the car has been acting up since. The traction battery is going from fully charged to zero then back to fully charged every few minutes. I'm also getting some idiot lights on.  I've zeroed them out and they come back. It all started from running out of gas. Can the traction battery be checked through the MFD?

[rrbcap]

@joesephwind When you say traction battery I'm assuming you mean the main hybrid battery? Did you run it far when you ran out of gas on the hybrid battery? That can be detrimental to the hybrid battery and is not recommend. You may have totally discharged your hybrid battery. There are some diagnostic checks in the screen I mention you could have a look at to see if there are any error codes. Could be your generator too but strange it happened after running out of gas.  Good Luck.

[nicknco66]

This very helpful as the battery fails. What if the battery is dead? Can you charge it?

I left my 2008 Prius sit idle for months because I couldn't drive. Now no light comes on with or without the key in the ignition slot. The dome light is dark when I enter the car as well. I'd like to know if you tried recharging the battery before replacing it.

[rrbcap]

@nicknco66 a little late response :). You can charge the 12v battery from the terminals under the hood. There is a black box. Pop that open and you will see a red cap for the 'hot' lead for the battery charger.

[joesephwind]

@rrbcap I drove max a 1/4 mile after it went screwy, most of that was coasting. Yes, Traction battery aka main hybrid battery. 2004 Prius. I'll go fiddle around with it, thought you might be up for another awesome video on how to check the traction battery. You'd get tons of hits, I just checked an there aren't any videos on it on here.

[claytonfuller]

Wish I'd known about this earlier. My 17 y/o son was driving in the middle of the desert at freeway speeds when it just shifted into neutral and shut down. The display showed a diagnostic code that made it sound like there was a transmission problem. He was able to restart the car, but it would keep dying after 10-20 miles. The nearest repair shop had no idea what was wrong. Towed it over 300 miles, only to have the Toyota dealer tell us it was the battery (and charge us $350 to fix it)

[m0bob]

Excellent piece of information, but my Prius is parked outside the house with a totally flat battery :-(

[rrbcap]

@not2L8t I know! I told my Mom I wasn't going to get my hands dirty and even attempt to install it for that price. I had over 100 bucks in mine and that was with a 25% discount from toyota. I'm pretty sure the parts manager got chewed out by his boss. I took down his name and double checked the price with him so we wouldn't have any problems after they installed it and invoiced us :)

[not2L8t]

@rrbcap That's CHEAP. My Optima was $130. Dealer wanted 270 + tx. Laughable.

[rrbcap]

@not2L8t Glad you found the video useful. I just got back from Florida and tested my Mom's Prius and she had a dead battery. You are right though, you should see an increase in MPG. The hybrid battery will keep the 12v auxiliary charging which in turn will cause your motor to run more often. My Mother got her battery replace by a Toyota dealer. They charged her 75 bucks for the battery and a 15 dollar installation fee. I think they must have though it was a regular battery.