2005 Prius 12V Battery Questions

Because no one here has *ever* reported getting engine problems (or any other type of problem) with 12V battery voltages at that sort of level. I'm just telling it as it is, so as not to give false hope to the OP that the new battery is going to magically cure anything, because it wont. The OPs original battery was only very slightly weak, and the Prius is very tolerant of slightly weak batteries.

The weird issues that people sometimes report with weak 12V batteries typically don't happen until the ig-on load voltage falls to 10.x or even 9.x volts.

 

Lets break those numbers down.

- In car charging, 14.1V.
Perfectly healthy.

- Light load (acc mode, dash display and minimal systems powered up), 12.3V.
Perfectly healthy.

- Somewhat higher load (ig on, all systems powered up), 11.8V.
This reading shows slightly higher voltage drop than ideally expected, but only by about 0.2 to 0.3 volts. This is NOT indicative of a significant failure (like a dead or shorted cell) but could be indicative of a slightly higher internal resistance than ideal. It could be due to a small amount of sulphating, it could be due to a slightly low SOC due to short trips or infrequency of use. It could however be entirely unrelated to the battery, and due to a slightly higher load drain during the test. Did the OP have any fans running, or rear demister, or parking lights etc, during the test? We don't know, but I can tell you for sure you can get readings around 11.8 to 11.9 volts with a brand new battery if you turn on the rear demister and/or headlights during the ig-on test.

 

No point creating an argument here because we both have valid points to make.

A battery that is getting weak will not heal itself; it only gets worse.

Except for the charging voltage, which really has nothing to do with the health of the battery itself, those readings are not "perfectly fine". They indicate that the battery is failing OR there is a bad connection somewhere. This assumes that the tests were done correctly.

It may not fix all the other symptoms he has......or even any of them, but it is something that needs attention; even if that is just re-testing on a regular basis for a while.

 

You appear to think that me stating my point of view constitutes starting an argument. You asked me to justify my opinion ("What's the point of questioning his reported results now"), and I did so.

My assessment of this has not changed. I still believe that the 14.1V and 12.3 volt reading were within the normal range and the the 11.8 volt reading only slightly low - and not low enough to cause any abnormal operation. You asked me why I said this and I'll tell you again, I said it because it's a fact.

 

So what exactly leads you to believe those figures do NOT indicate a problem that needs to be watched ??

I have 50+ years of experience in electronics and I can assure you that in most cases it is NOT "normal".
In this case, apparently the dealer agreed because they changed the battery.

The 14.1 should not enter into this discussion at all. I agree that is OK........but it is NOT a measure of the
health of the battery itself.

I don't think that your opinions expressed are "facts" at all.
I think that leading people to believe things are "fine" when they are not is a dis-service to those who are
asking for help.

 

How about sticking to what I actually said instead of trying to put words in my mouth. I never said it doesn't have to be watched. I said that the ig-on (loaded) voltage was slightly lower than expected and that the battery probably has slightly higher internal resistance than is ideal. I also said that a new battery will not improve the performance of the car in any measurable way, and I stand by those statements.

What makes me believe this? First hand experience rather than some forum dogma, that's what. My previous battery measured 12.3 in accessory mode (after sitting overnight) and 12.0 in ignition-on mode from the time I bought the car (secondhand) in 2009 until it started seriously degrading in 2013 when I changed it. All that time I had not one problem. Even when it started to seriously degrade last winter, it dropped to 10.8 volts in ignition-on mode, it still started perfectly and experienced no degraded performance. It had been dropping fast for a few days, and on the day it dropped to below 10.8 volts it still started fine and allowed me to drive it to the battery retailer to buy the new battery. When I returned to the car it started fine again and allowed me to drive it home, where I installed the new battery. I didn't even experience a drop in MPG, zero bad things happened.

Now I've got a new battery that's less than a year old. It measured 12.8 volts straight off the shelf and has a built in hydrometer showing it's fully charged. It still only reads 12.4 volts when I measure it in the car (accessory mode) and only 12.0 to 12.1 volts in ignition-on mode. And guess what, I'm still not experiencing any problems. I still get over 55 MPG. And if I turn the fan on full then that 12.0/12.1 drops to about 11.9 volts. This is not a problem. All batteries have some degree of voltage drop when greater load is pulled from them, and the Prius does not require a 12V battery with a super high load current capacity. You could put a 2000 cranking amp truck battery in there if you wanted, but you'd get not one once of extra performance out of the car.

Please stop telling me things I already know. It is a measure of the DC-DC converter voltage, but if the battery is very seriously sick then this voltage can be off.

BTW Easyrider. Can you please measure the stats on your battery. Not using a meter but using the service mode menu of the MFD when the Prius is powered on. Few people get much more than 12.2 volts for the ig-on measurement. Put your fan or headlights on and report back.

 

"- Light load (acc mode, dash display and minimal systems powered up), 12.3V.
Perfectly healthy."

Whether or not 12.3 indicates "perfectly healthy" depends mostly on the no-load voltage before the teststarts.

I'm done. You aren't getting the point that absolute statements like that are often misleading and sometimes downright wrong. Let the readers come to their own conclusions.

 

Double post deleted.

 

Well lets just say that readings around 12.3 to 12.4 volts are extremely typical for this particular test (Acc mode, MFD measured, after sitting overnight).

You do realize that the OP just wasted a stack of money replacing an almost brand new optima battery based largely on your advice don't you?

 

I wouldn't be surprised if Optima had a bad batch of batteries in 06/13. The one that I'm returning for warranty replacement was that time frame and it would hold a charge beyond 11.9 volts with no load.

 

Ill check my date code too, although Im pretty sure its around 3/12 or 6/12.

Maybe every summer in June, Optima'a Quality Control supervisor goes on vacation?

 

Yeah that would explain it. LOL.

BTW Priusguy. What are the three voltage measurements you're currently getting with your optima battery (acc mode, ig-on mod, and ready mode)? Have you done the test lately?

 

If you give me a hot minute, Ill run to my car and check!

EDIT: Ok I just checked. And the results are worse that last time, even though Ive been hooking up my smart charger about 1x week.

Accessory Mode: 11.9v

Ig-on Mode: 11.1v

Ready: 14.1v

I should add that I drive the car ~50 miles per day (usually more) and that I keep the car in a heated garage at night

 

I "be thinkin" I am glad I took Ron and Patrick's advice and got the Toyota TrueStart battery...

 

I be thinkin' you are a scholar and a gentlewoman!

And I also be thinking that when I warranty exchange my Optima, Im going to place the new one on Craigslist to recoup my initial investment. Then Im going to do exactly what you, and many others have, and waltz right over to my friendly Toyota parts department and buy the OEM one. I already called and they want $188 for it.

Optima experiment = fail (at least for me)

 

I should do the same. Sell it here on Priuschat.....

 

Ar that was a long "hot minute", I thought maybe the spiders had got you.

Yuk that's really bad. Much worse than the OPs.

BTW. I see that JC91006 successfully got a warranty replacement on his poorly performing optima, maybe you should have another try at returning yours? Edit. Ok I just saw your above post that you are going to get a warranty replacement. Good work!

 

Im gonna call Advance Auto Parts right now - when I called a few weeks/1 month ago, they had 1 on the shelf at 1 store. Nobody else had one. I asked the kid on the phone about how long it had been sitting on the shelf, because I do NOT want a repeat of my last experience and he said they just opened a month or two ago and the battery was fresh. Im going to call the kid back and see if he still has it and before I run down there, if he can multi-meter it for me on the shelf and tell me what its at. If its less than 12.6v, Im not even going to bother.....

 

Beautiful... the AAP that I had spoke to a month ago doesnt have the Optima anymore, doesnt show any in the warehouse and cannot order it directly from Optima Im now on the phone with another store just to verify this is true.

EDIT: 2 Advance Auto Parts stores are saying the same thing! This clerk is saying AAP is no longer carrying that battery. I almost want to call a 3rd store to verify that its true...lol

I might be able to bring it back for a full refund though.

 

Slickdeals web site has a $50 off $125 Advance coupon on their front page deals at the moment...of course yours is a return....??

And, I just checked and it is an online coupon only, ...so...nevermind....

But in my "area" several Toy dealers had "coupons" on their Web sites (usually buried on the parts or service subpage) that gave various discounts such as 10 percent or so on parts. ....