At what point do you replace the 12v battery?

It was 11.9 volts this morning, definitely on it's way out.

 

It seems the testing procedure is to charge the battery at 4-5 amp rating for the S46B24R. Turn charger off. Switch high beams on for 30 secs. Measure voltage at battery terminals:

12.5 V or higher OK
11.0 to 12.5 V Recharge
Below 11.0 V Replace

My father decided to listen to the radio outside of Church (about 1 hr), which killed the battery. AAA jump started. He came home and I charged it. Yesterday gave a healthy drive of about 35 mi and sat overnight. I measure voltage on two multimeters 12.47 V and 12.46. Charge, pretty much the same immediately after charging, no need to turn on high beams for 30 secs first. Charge again, similar results! Argh! I can’t keep charging it all day. Don’t want to try the high beams without a replacement battery ready...

I guess it’s time to buy a new battery......

 

Well, I have to come back and correct my last statement!

The first charger I tried, both are Schumacher brand, has a setting for 6-2 amps charge/maintain. This was the one that would stop and immediately show 12.4x V.

The second has a 3 amp setting. This seemed to do a lot better. I unplugged and replugged in to see it start charging again a few times. Last time when I plugged back it noted 97 % charged, and quickly filled up.

Sounds like it is a good idea to charge it slowly. On the battery itself is a label that notes a rate no greater than 4.2 amps. In the FSM it noted 4-5 amp range.

I like the Schumacher brand because it includes settings for AGM and Gel, as well as Standard....

 

I just ordered one of these!

New 46B24R 12V 46Ah 650CCA Lithium Iron Phosphate Battery LiFePO4 for Automotive | eBay

I splurged on the 2 year SquareTrade warranty just in case there are any reliability issues. Otherwise it comes with a 1 year warranty from the seller. (There is a 1 year Accidental Damage SquareTrade warranty that aligns with the original warranty, but covers accidentals...

Will report on more later.....

 

Years ago there was a fad with lead acid batteries that have a jump start feature. This sounds like the same thing but more hi tech.

 

My 82 year old mother and 88 year old father will never get all the stuff out of the rear to access the button. (I’m not even going to bother telling them about it). But the LiFe batteries are the real deal, (I believe). I would have probably scrounged my pennies for a Braille version but they do not make one in this specific size, are in the $2000 range I’m guessing for this size, and do not have the backup built in, which I could take advantage of.

I’ll definitely share my findings. It’s been shipped!.....

 

I have a 2010 Prius with 190,000 miles and have the same 12v battery in it. Is that normal?

I also have the same brakes and they work great....... That's insane!

 

Just for giggles have the battery checked with an electronic load tester, see what it says. I would suspect the car never sits idle long, and does a fair number of lengthy drives. I'd say regardless of it's condition, it's time.

You have the "same" brakes, equals you've yet to need to replace the pads. Be careful though: don't conflate pad thickness with the need for a brake inspection. Have you ever had a proper brake inspection? Not the 60 second look-over when the tires are being rotated: an in-depth inspection, where the calipers are pulled off the rotor, the caliper pins pulled, inspected, cleaned and relubed, the pads have thickness checked, are cleaned up up and reassembled and relubed, and the rotor is checked for thickness and runout.

Check in the Warranty and Maintenance booklet: Toyota USA has been telling you to do this every 3 years or 30K miles.

 

We also have the 2010 Prius and has 135K miles right now... same 12V battery, BUT MPG has dropped to 38! Replace?

 

9 year old battery, yes replace it. That might be some sorta record. Still, not sure that would the cause of the dropped mpg. Might be, at least in part.

Ever looked into EGR and intake manifold cleaning?
New tires recently?
Recent brake work?
Change in your drive, say from a long commute to a lot of short trips? Or?

 

What's the part number for the 12 volt battery for the Prius V? As far as I know, Mine still has the original 12 volt, and I'm creeping at 125,000 miles. I suspect I'm due for a new one soon. I haven't tested it yet. I saw a youtube video that you can go through the stock radio settings and it will display your voltage on the stock radio. Of course, you have to turn the car on and off and do a couple other tricks to do it, but it seems legit.

 

You want a S46B24R Battery. The Toyota one should have a 84 month warranty. (prorated after 24 months)

Here is a cheaper one: www.amazon.com/ACDelco-ACDB24R-Advantage-Automotive-Battery/dp/B010GKJ8F6

I would use a cheap multimeter to get battery voltages over night without turning the car on.

www.amazon.com/AstroAI-Digital-Multimeter-Voltage-Renewed/dp/B07K8DCPSJ

 

Mine failed in my 2012 after 7 years plus.

I got this one.

Duracell Ultra Platinum AGM Battery for 2012 Toyota Prius L4 1.8L 325CCA Hybrid Car and Truck - SLI51PAGM at Batteries Plus Bulbs

I like the convenience of Batteries Plus and the four year full price replacement warranty. Prorated warranties are only for the seller to establish customer loyalty.

The fit perfect and install was absolutely easy.

 

You replace it before it leaves you in the lurch. Your battery’s longevity may vary.

 

Battery in my Cobalt is 11 years old

Volt is 7 years old.

Will replace upon failure

 

You can check it first... I posted Toyota Techinfo instructions a while ago. From memory, stop engine or charger, turn on high beams for 30 secs. Measure voltage at battery terminals. Either below, or at or below 11 V, replace. I can’t remember the rest. (I hope I got the 11 V part correct)...

 

I'm not a fan of this method after having to replaced many alternators because of it on conventional vehicles. It stresses the alternator too much towards the end of its life.

 

I only just saw this thread. How is that battery doing? I saw in one of the pictures on the Bay listing "Warning! Don't use Lead-Acid Cattery Charger" -- but isn't that what the Prius's charging circuit is designed for?

 

Gen 2 is very gentle, Gen 3 is more aggressive, Gen 4 is smart.

 

So far so good.

That’s a very very good point that I struggled a little to figure out. Thank you for asking. (So I can quell any concerns). The charging system is designed for an AGM lead chemistry battery, and their instructions specifically say NOT to use a lead acid battery charger. Hmmm, how can they claim it is a proper replacement?

So when I received the battery, there was an instruction booklet. It gives a method to verify if things are compatible. I believe it was given as a charging voltage range with a minimum 13 V maximum of 15 V. (If I can find the booklet I will come back and post the specifics). I then checked my “service manual” that I tediously downloaded (document by document) from Toyota’s Techinfo site. Specifically I looked for a document to check the charging system function/if it is working properly. It just so happens the voltage range (please note the 13 V to 15 V may not be correct/exact because I am pulling from my memory), but it matched up perfectly, or at least on the maximum voltage side, so I knew the battery is compatible (again from my memory).

One thing I should note is that the one I got did not sit completely flat due to it being a little bit too big on the bottom. I added some washers under the mount and a longer bolt to tie the battery down. The battery sensor on the bar does not sit perfectly on the battery, but I’m not too worried about it. The seller did note they will make an adjustment to future batches so this does not happen again. Not sure they sold out their original batch yet but hopefully they did...

I have a thread on falling in love with it, I will try to look up the specifics there and if I can find the corroborating evidence....