Yet again...another 12v battery question

Just based on the age I would recommend replacing unless you want to risk getting stranded one day.

 

The age/time is about right. But some go much longer. The readings are not especially bad as the resting # is above 12v instead of below. And the spread between the resting and the acc readings are not too bad either. If you check the resting # at the jump point under the hood it may read .4-.5 more than the 12.1. I would slow charge it at 2 amps or less overnight or until you can get to a full charge. Most chargers will shut off when it's fully charged. Charging like this now and then may extend the battery life. Keeping a jump starter in the car is not a bad idea. Researching a new battery is also not a bad idea.

 

Yes, I've done it before. Patrick Wong has too, IIRC.

I have Amazon.com: TecMate TM-141DUAL OptiMate 4DUAL 0.8Amp Weatherproof Desulfating Charger/Maintainer: Automotive. I posted battery tender/maintainer suggestions | PriusChat but never got much of a response.

 

How to check the 12 v battery status reading on the display? Thank u in advance for ur responses

 

Weird stuff happening? MPGs dropping? Test The Battery

You can report the 3 readings back to us if you like.

You can also check the resting SOC (state of charge) from the jump point under the hood, in the fuse box on the drivers side, under the red cover is the positive connection. The negative connection is the strut bolt just behind the box.

When jumping from this or battery make certain the connections are correct the first time. You may not get a second chance this side of a great expense.

 

*sigh* I just got 12.5 volts on mine this morning, cold (no key, no acc, etc.). Tested it on the fuse box positive jump point with a Fluke DVM. Still getting crap MPG. Maybe spark plugs? Tyres are 35 front 33 rear.

 

Testing it through the system has the advantage of also showing the spread between the resting and acc volts, as well as the charging voltage. You will likely see a .4-.5 volt difference from the jump point to the MFD.

It seems to be a number of relatively minor things that can cause a difference in mpg too. I would try running 40-38 lbs of air. I just changed my oil to 0-w-20 and believe I see a slight improvement. Running the electric heater I think may cause a decrease. Learning to coast sooner into slow areas, to stops signs and lights helps. Of course the terrain and type of driving will afect the mpg. There is a whole sticky forum on the mpg subject.

 

I have a 2006 Prius with 130,000 miles on it and I still have the original 12 volt battery. My independent mechanic tested it and it is still holding a 75% CHARGE. I will probably replace it before NEXT winter as I live in the Northeast. FYI I still have the original brakes which are about 45% worn. I recommend replacing the plugs every 60,000 or 70,000 miles even though the manual says to change them at 150,000. I just replaced the PCV valve for the first time. My Antifreeze looks as clean as the day it was installed. I replace the AIR Filter and cabin filters every spring. Its a 5 minute job.

 

What does it read if the car is in ACC (not READY) and the headlights are on?

If you are in a cold climate (snow) and this is your first winter with the car, it's the cold weather. The factory pressures in the tyres hurt noticeably also. Increase them to 42/40 PSI front/rear for a few tankfuls and see what happens.

 

Here's my 12-volt (12v) battery question: I see a lot about replacing the "reserve" battery, the one accessed from the rear door, but I'm not clear on how to buy a replacement for the "starter" 12v battery, under the hood. When looking around for one, what do I tell them besides "the starter 12v battery, not the reserve 12v battery"? I can only find one by Optima and one by Bosch, and they run $209 and $189 respectively.

How can I be sure I'm buying the replacement STARTER battery? (Thanks in advance!)

EDIT:
--I think I figured something out. I've read about the "starter" battery and the "reserve" battery (as different than the big, main hybrid battery). But I am getting the impression that they're the same thing. There's no battery under the hood, just the jumper terminal. -Right?

 

Your edit is right, there is no 12V battery under the hood, just the jumper terminal. The car has only one 12V battery, located in back.

 

Lucky44,

The Prius is unlike a conventional car. It has two batteries. One is normally referred to as the traction battery. The other is normally referred to as the auxilliary battery.

The traction battery is sometimes called the big battery and or hybrid battery. That battery is a rechargeable NIMH which operates at high voltage. The battery is charged by the ICE (gas engine). The battery is used along with the ICE to power the electric motors that drive the car.

The auxilliary battery is sometimes called the 12 volt battery. It is used to "boot" (start up) the computer's on board the Prius. It will also power certain 12 volt systems whenever the Prius is not in "Ready" mode.

As far as the auxilliary battery replacement is concerned you have three options.

1. Optima Battery (Yellow Top)
2. OEM Replacement (Toyota True Start)
3. Exide Brand

Depending on your location you may find alternative batteries other than what I specified above. The batteries I specified are available in the United States.

Be aware that the 12 volt battery is specially designed for the Prius. It has small posts on it, and is also a AGM type battery that has a vent on it. The vent should be connected to the vent tube on the Prius. Average price of the battery is usually around $200.00 Also, if you ask Toyota to change that battery for you, you may be shocked by the labor charge. The stealers around here are charging $120 and up just to change the battery. If you do it yourself, you should be able to complete the job in less than two hours. Some report doing it in 45 minutes. I am handicapped, and was able to change ours in a little over an hour.

If you are somewhat mechanically inclined, you should find the R&R of the battery to be fairly simple. The only tools you need are a couple of sockets, wrenches, (both 10 and 12 MM), a flat blade screw driver, a small hammer, a ratchet, and some extensions. Make sure you disconnect the negative first where the cable attaches to the body, and then reconnect it last.

Ron

 

Thanks Fuzzy and Ron. That's helpful.

I found this video really useful for guiding me through the 12v battery swap. It is not complicated, as you said, Ron. But it has its patience-trying moments.

This post was helpful too: 12V Battery Replacement-- A Preemptive Strike | PriusChat

The battery I chose was a Bosch 51-440B-AGM, and it was about $189. It came with a 4-year warranty. The only odd thing about it was that the little vent tube on the top was on the wrong side; fortunately it seems that they made it so you can swap it from one side to the other (exchanging a plug for the vent tube).

That took me about an hour. It would have been faster if I hadn't kept dropping one screw while putting it back (to hold the HV battery vent tube to the side of the car). Fortunately, I have a cheap telescoping magnetic retrieval tool, and it was a lifesaver!

So it is all back together...and it isn't working at all! LOL. Seems like there's no battery connected at all. I'm not sure if the battery isn't charged enough (I put it on a 1.5-amp / 12v trickle charger for about 4 hours, and it's dated about 5 months ago), or if I did something wrong. I've read of people saying you should connect a decent 12v battery in parallel to prevent some problems around loss of power in a swap. But other said it only loses your radio stations and such. -I have an electrical multi tool at work, so I guess I will have to bring it home tomorrow and see what it shows about the battery.

EDIT: Ha ha ha. Oh the humility of it all! I forgot to finally reconnect the negative terminal to the car (inside) body! Kinda makes it impossible to get any current into the system! It seem to have lost a bolt along the way somewhere, but I had a spare that works fine.

Now! Everything seems to be fine (car starts, ICE comes on, electrics work fine, including headlights, -clock reset to 1:00- etc.), except for one thing: the "HUD" information like gear, speed, odo, etc. is black...nothing showing. But some of the "dummy icons" are coming up (e.g., airbag info, etc.). Could a fuse be blown?

 

Hi Lucky!

Glad to hear you got the battery swapped. In reference to the screw that gave you the problem. That is the trickiest part of the whole job. The way I did it was to put a little lithium grease on the head of the screw, then put the head of the screw into the socket with a long extension on it. I made sure that the screw would not fall out of the socket by tapping it. The grease will hold it in place if you use enough. Then I simply lined up the mounting bracket with one hand and with the other hand I inserted the end of the screw through the hole on the bracket and turned the extension clockwise until I felt it become snug. Then I simply put the other bolt in and snugged them both up with the ratchet.

If you ever do the job again, try the grease trick. It is a old mechanic's trick that goes way back. You can always wipe the grease off after the job is done if you are concerned with dust, dirt, etc.

Good luck to you and once again "Welcome" to Prius Chat!

One thing I have to ask. Did you check the voltage of the new battery before you installed it? I note you are saying nothing is working. If you did everything properly and the battery is fully charged, you should have power if everything is connected properly.

Ron

 

OK, a second follow up (the first was an edit to my last post).

I went back a few hours later, and everything seems normal. It's as if the system needed a little time to settle in. Thanks again for the help, all.

 

Hi Lucky,

Just for grins, do you have a link that you could post or at least write out in a post like webpage dot com/org something like that?

I tried finding the battery you referred to by the numbers you gave and did not have much luck.

It would be very helpful to the community here since the Prius 12 volt battery is limited to just a few vendors it seems.

Again, glad to hear you got everything sorted.

Regards,
Ron

 

You know, the guy at the Pep Boys said that was the part number, and the receipt says that too, but I can't find it online anywhere either (under Bosch's site or elsewhere). I can't open up the case again and look the battery over now, but I'll try sometime soon.