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

[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.

[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 :-(

[not2L8t]

Great summary of voltage check. Just replaced my 2006 battery with the Optima D51. No problems, voltage is within norms. Easy to switch them out, and I'm a noob. I connected a little 12v 1.2Ah battery to my jumper connections in the engine compartment, so it saved all my electronics settings while the old battery was disconnected. Getting 10-15% better MPG now with new battery. The system was apparently having to charge the old one all the time. which kept the engine running more than normal..

[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.

[not2L8t]

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

[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 :)

[UnitedPebbles]

Johnson control Optima battery should be your choice of replacement for that aux battery!

[naresh1607]

I really appreciate if you can let me know how to check the same for 2003 Prius model?

Thanks.

[amaroook]

Thanks for a great video!

[knitter1231]

Thank you so much for posting this. We've got a 2006 and a 2007 Prius and I will run this check on them. I also want to thank you for the video of changing the battery. I knew where it was but it was nice to see what's involved in changing it. I'll be doing it myself and saving some money!

[bbwmaxie]

Yesterday I went out and powered up and it slipped into N and I couldn;t get it out. I couldn't turn it off or shift it into p. It's totally dead. The dealer saud to get a jump and come in and for 35o!! with labor he could replace it. Thanks it's dead now I'll cll for a jump and see what I can do to pay much less.

[dkkdvd]

Thanks for the video. Might I ask how much the replacement auxillary battery was and where you purchased it? Did you go through a Toyota Dealer or have luck somewhere else? I've heard the replacement batteries are quite expensive.

[rrbcap]

@dkkdvd I think I got it for under $100. I have a friend who can get OEM Parts at a decent discount. I want to say the battery is under 140 bucks without a discount. Good Luck!

[tri400]

i thought this was a hybrid car and the battery is a big huge NiMh battery or Lithium Ion battery

[rrbcap]

@tri400 Two different types of batteries. You have the Hybrid battery which is what you speak up, and then there is the 12v auxiliary battery that every car has. The Hybrid battery is warrantied to 100K miles. I know people who have over 200K on their Prii and still no problems with the Hybrid battery system.

[rrbcap]

@sowpur I knew someone would comment on that :). It is a 12V battery so I would imagine as long as it stays within 12V you would be fine, but in not an expert in battery voltage.

[sowpur]

If I'm not wrong I think you said a good battery should be 12.4 to 12.8 V, but your new battery is reading between 12.0 to 12.3V So is it ok if the battery reads between 12.0 to 12.8V?

[bigbeemerbiker]

I like this. I've just bought a used 2008 Prius MkII that seems to work fine, but it hadn't been driven much in the month before I bought it, and I thought it would be useful to check the 12v battery state. So I think I'll have a go at this. Only one thing worries me -- mine is a UK Prius rather than USA. Can you say whether it likely to be different for this task (especially in any way that might cause me to wreck some internal software settings?

[rrbcap]

@bigbeemerbiker Glad you enjoyed. I'm not 100% it is the exact same way for a UK model but I think you will be fine with running the test. You won't break anything :) Worth a shot. Good luck! Let me know how it goes.

[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.

[ronald3100]

Great Video

[rrbcap]

@ronald3100 Glad you enjoyed. Thought it was a good Easter Egg to share.