Did toyota sell me a defective 12v battery??

welcome! it's hard to say. 12.4 volts is low for a new battery, so you need to have it charged. it should be around 13 volts.
but whether the battery is defective, or there is something wrong with the car is going to take some detective work.

 

If it turns out to be defective, there is a 84 month prorated warranty for the Toyota TrueStart battery. The dealership should be able to exchange it for you.

 

See if the manufacture date is on the battery. Sometimes they will sell you a brand new battery and its actually older.

 

Has the battery been fully charged? Unlike a traditional car, charging takes many hours (6ish) of running the car on a Prius. Or you can use a charger.

 

This.
If the dealer installed it, they should have charged it.
If YOU installed it, you need to do that.
12.4 is low. 11.9 is VERY low.

After the new battery is charged up, then you need to measure the voltage while the car is "running".
That needs to be a bit above 13 (at least .5 volts higher than the battery's resting voltage). If not, you have charging system trouble.

After all of that.......then yes you can consider that your new battery might be defective.

 

The dealership will (for sure) have electronic load tester, will be able to assess it, come to a verdict. I use a prosumer level Solar BA5, does the same thing.

And yeah, if you want to stay "on top" of all things 12 volt: read up, have a digital volt meter, something like the Solar BA5, and a smart charger.

I'd suspect dealerships won't charge a new battery, just install it and assume you're going to be driving it enough to keep it healthy. But it definitely doesn't hurt to hook it up to an appropriate amperage (3~4 amp) smart charger at the outset. This is one reason it's likely better to do your own install, and clean up the cables and posts, do it right.

 

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FWIW: I have had a dealer incorrectly give me a free "battery is OK" diagnosis. Best to test yourself. Have you found the Prius computer self check method (no meter needed) here on priuschat?

 

That sounds a bit more like the combination meter problem than a weak battery

Did you also check that it was about 14 volts (charging) in ready mode?

 

G'day,

As a toy for my new Prius c, I bought a cheap dual USB plug (ebay, from China, about $4AU, and a few weeks wait) for the Prius's accessory socket so I could watch various volts and amps and degrees in the car.
Well, my passenger can watch them as in the c, this socket is just out-of-sight for the driver when driving.

With the Prius 'Power' on, the battery voltage reads about 14.5V while the traction battery/I.C.engine is charging the 12V battery (like the alternator in an old-fashioned car, or for those of my generation, the generator in a really old car).

With the 'Accessory' on (no foot on the brake when hitting the 'Start' button), the USB device displays about 12.5V and this slowly drops as there is some power being used by the car in this mode, i.e. by the 12V battery.

The attached images from my mobile phone of the USB-plug in my c's accessory socket were taken about a month apart and show good reproducibility, at least for a four months old car through a summer.



So, depending on how/when you measure the 12V battery voltage, you should see about 14+ volts or about 12+ volts.

For me, I'd be slightly worried if the 12V battery read 11.5V or less with the engine/'Power' off. Less than 10V is my remembrance of past winter-battery failures - they hardly ever fail in summer here. We don't 'do' snow here in Oz so how that affects a lead-acid battery I don't know. A Scandawegian may know.

My thoughts are then I don't see you have a faulty battery as such, but there may be a problem in the charging of the battery by the car.

A test of the 12V battery under load by the dealer or an auto-electrician should highlight if the new battery is not up to scratch - which could be the cheaper outcome for you as I'd fear there might be a deeper problem to locate then fix.

I'm hoping I'm wrong.....but...

Good luck whatever,

David S.

 

New car battery's aren't made like they used to. Different chemical structure and Rhos. You have to drive alot on a g2 Prius to put a good charge on it. And if its not able to charge the battery it will throw all kinds of check engine lights. Your probably repeating your same short distance driving that killed the original battery.

I do know for certain at about 11.7 volts it throw a big red exclamation point on the dash at boot up. Only on for an instant . Is very noticeable as it is not on the start up bulb check routine.

Buy a charger and throw it on the charger overnight in 2 amp mode. See how long it takes to turn on the FULLY CHARGED 13.8 volt light.
Don't waste your time load testing at the dealer as I have seen hundreds of posts here they can't seem to do it right.

As a reference my 4 year old Optima is usually at 12.75 volts in the morning before I start my 20 mile commute. But it is on the charger at least once a month.

Like everything else in your life it will take some personal intervention.

 

Actually, the CM problem is weather-dependent, as stated in Toyota's extended warranty policy. It usually happens on cold mornings. I agree, this sounds more like the CM.

Since the extended warranty is expired for your car, one option would be to pursue getting yours repaired. You can find shops on eBay. Here in the US it costs just over $100 and takes several hours of DIY work.

 

I'll throw my +1 at I think it is a CM problem too, as andrewclaus stated it shows up in cold weather. It was actually the very first thought I had as I read your opening post. Unfortunately I think you are just out of the warranty replacement for the CM TSB recall.

A member here, Texas Hybrid Batteries, offers a fix service, if you wish to contact them. It will involve you removing the defective one and reinstalling either your fixed one on return or he can send a reworked one ahead of time for you to swap and then send him your defective one. I think his price is reasonable for this service.

Also +1 on ensuring you charge the battery to full with an external automatic battery charger, @ 3.3 - 4 amps. Unless of course you like changing out batteries prematurely.

 

Alas they don't always come up with the right verdict.
Most still use the "brute force" tester which was designed for starting batteries in NON-hybrid cars.

 

Unless it's a free test, don't waste your money or time.

 

Well ask, see what they're using. I'm using a Solar BA5, and nowadays any competent dealership, or a battery retailer, has a pro-level digital tester with printout capability.

They measure any-and-all battery types (you enter the type), let you know it's voltage and it's CCA, gives a verdict on how to proceed, ie: good, good but recharge, or a goner.

 

The key word there is "competent".

And it is always possible that an intermittent condition exists.......like sulphation shorting out a cell sometimes.

 

I'll let you have the last word.