Brand new 12 volt battery not reaching 100% state of charge

Take it for a long drive, see if that helps. Mine also stays around 11.2 in ACC and 13.5 driving

 

In my opinion I'd say the battery is still ok - and that 100% charge your looking for will depend on how long the vehicle has sat, and how long of a commute you take. It may reach it, or it may never reach it.

If it concerns you though I suppose you could get a battery tender.

 

In my experience, a external battery charger is a requirement unless you drive several hours every day.

Did you ensure the Yellowtop was fully charge before installing?

BTW, for an AGM battery, 12.1 - 12. 2 V is ~37 - 43% SoC.

 

Agree, trickle charge the new battery for a day, unhooked from the car.

What battery, a yellow top equivalent...

 

prius is virtually incapable of fully charging the battery. it is more of a maintainer. you need to start with a fully charged battery before installing.

 

This.
Most new batteries need an overnight charge before use and the onboard charging system is designed to MAINTAIN a full charge and might not be able to recover a full charge if the battery gets near dead.......which your readings indicate that it is now.

If it consistently sits at 12.1-12.2, you should be concerned......as something is not right.
What is the voltage when the car is "running" ??

P.S. Since the 12 V system does not actually run a conventional starter, once it gets "full" it should be easy to keep it there (around 90%).......and an external charger should not be needed unless it sits for weeks at a time.

 

How are you measuring the voltage?

 

Fully charge the 12v battery and I think you'll be fine

 

Check the voltage of the battery first thing in the morning, with a decent quality digital multimeter. It's possible the replacement battery is a dud, but hard to say till you measure carefully. You should be seeing at least 12.6 volts, with a brand new battery in good shape.

Did you buy it locally? Maybe the store has electronic load tester, can check it? For DIY, something like Solar BA5 (or BA7) is good to have.

With a volt meter, you want to check after the car's rested overnight, after a charging session, or even after a good drive, it'll be up a bit, what they call "surface charge".

FWIW, the Yellow Top is nothing special. I actually have one in ours, the price was good when I was shopping. But I've read they're somewhat high in Cold Cranking Amps, but fall short in Amp Hours. It's a bit over my head, but next time (if that happens), I have some other ideas.

 

NO not really.

There is no good reason to have a "deep cycle" battery in a Prius.
But it's too late now. It won't hurt anything.

Now would be a really good time to invest in a small (2 to 4 amp) fully automatic battery maintainer.
It might take a LONG time (like 24 hours maybe) to charge a mostly dead battery but it should work.
They can be had for $35 or less.

 

My CTEK 4.3 charger does have a setting for coil-wound AGM's (Like the Optima Yellow Top), basically charging at a slightly higher voltage. You can charge using that setting, or the regular setting. And a regular (smart) charger will work fine as well.

FWIW, we're coming up on 3 years with the Yellow Top now, and it's still like new, assessed with a Solar BA5. Still, I'm the poster boy for obsessive compulsive battery maintenance: we don't drive much, and on idle days I always hook up the CTEK 4.3, it cycles and stays on, till the car is next used.

 

Wow... So many comments in just a day... Back in the 90's Yellow top Optima's were the very best, especially among the car stereo crowd, but they sold out and their battery plant moved to Mexico and they've been making total garbage batteries ever since.

One of the sales reps is on Prius Chat and he's blatantly admitted than when people return defective 12 volts batteries that don't hold a charge they just charge 'em up and sell 'em as brand new without even investigating why the battery is broken because they always think the customer is wrong not them.

Get your money back and buy a real battery! If we had consumer protection laws the indictments against this corrupt company would of been handed down long ago and they'd be out of business entirely by now!

Because Prius 12volts don't need cold-cranking amps to turn over an engine starter like regular cars, the primary function of the 12volt is equivalent to a back-up home power supply battery to power computers. So YellowTop can get away with selling garbage to Prius owners and they're non the wiser. But try jump starting a big old V8 engine with your Yellow top battery and the starter will barely turn over.

The best 12 volt with near double the AMP hours of the recommended replacement battery is the most common battery that stores like Batteries Plus sells for wheelchairs and backup power supplies and because they seel so many, they only cost ~ $130. You have to add longer bolts and bushings to get the terminals to connect properly, but that's pretty easy to figure out. And most important, they sell so many of these batteries you'll never run into a problem like an Optima that's been sitting on a shelf for years because anyone who knows about batteries wouldn't spend a penny on that junk!

 

Here's the truth with lots of links to the complaints too:

"This company, retained several nationwide unsatisfactory records with the bbb for failing to respond to consumer complaints (links below).

Along with having been issued 19 individual violations from the state enforcement agency, 'consumer affairs' (bar).

Specifically, but not limited to, violating several sections of the business and professions code depicted below:

Section 9884.7 (a)(1) false and misleading statements
Section 9884.8 invoice requirements
Section 988.4.9 (a) estimate requirements
Section 3373 inserting/withholding info to cause document to be false/misleading"
Defective Optima Batteries, www.optimabatteries.com - Defective made in China, Review 97327 | Complaints Board