12V battery - my readings seem low

10.4 rest voltage is definitely too low but you never know what a dealer would say. If there are more than one dealer near by you may call them and see what they have to say, and go to the one that's most sympathetic. Also the diagnostic on items under warranty should be free of charge I believe, ask when you call. Good luck!

 

You'll need to replace the terminal connectors if you install an aftermarket battery.

Regarding the 10.4V measurement, did you take a photo of this, to provide to the service writer?

If you take the car in tomorrow, let the service writer know that the battery is discharging over time so it will be necessary to let the car sit for a few hours.

Most dealers will charge for the service call unless the tech agrees that a warranted problem exists.

 

What may be of interest is that the 2G repair manual (2005 manual, page 05-423 for example) says that acceptable battery voltage ranges from 11V to 14V. (I don't have access to the 3G manual at this time.)

However the manual does not say under what mode the voltage should be read: for example, IG-OFF, ACC-ON, IG-ON, or READY. Nor does it list any prerequisite conditions, for example, allowing surface charge to dissipate before measuring voltage. So the manual doesn't provide very useful guidance to the Toyota service techs.

With most cars this isn't a big deal because each time you start the engine, the 12V battery is put to a good test and a slow-turning starter motor is easily identified by its sound. With Toyota hybrids, the condition of the 12V battery is a big deal because the ECUs depend upon clean 12V power and lots of flaky behavior can be traced to a marginal battery.

 

The car is a 2010, battery problems in the 1st year, right? I had the same situation with mine in 2005 and since they replaced it have had no problems. However as elucidated I made sure the battery was empty, while in the waiting line, and stressed to the dealership that the battery was bad and that I should definitely get a free replacement battery. They kept the car overnight and gave me a free loaner. They then very graciously replaced the battery for " For customer Satisfaction" and later mentioned that I must be very careful not to leave doors open, etc. I say B.S........go get'em tiger.

 

When it comes to battery knowledge, specifically the 12V, the dealerships are totally incompetant. They don't have any Hobbits or Bob Wilson. And of course no battery load testing equipment. BUT they do have a shelf of brand new batteries for which they may get 100% reimbursed. So don't be too sympathetic with them.
:cheer2:

 

You got it! :cheer2:

 

You have a bad battery. The dealer should replace it. If they don't, then you have a bad battery and a bad dealer.

If it's that close to dead now, when the temperature drops 20 degrees or so, it won't boot the systems anymore. Battery performance is very sensitive to temperature. A few years ago, a friend was leaving my house, and I noticed that his engine cranked slowly before it started. I told him his battery was questionable, and about gone. He said ehh, it still starts. 2 weeks, and one cold front later, it wouldn't start.

It was a good idea to help the dealer see the light. Drive there, shut down, then power back up to accessory (one step below ready). Run the radio and fan on high for a few minutes to take off the surface charge. This won't hurt a good battery, but it'll probably send yours crashing down below 10V.

FWIW, when mine gets flaky, I'm replacing it with an Optima.