Pre-Charge New Optima 12v ?

I just replaced the 12v battery in my 2005 after I was getting the weird symptoms that typify the battery was going bad. In diagnostic mode it was reading about 11.4 - 11.6v. I replaced it with Bosch battery on sale for $145 from Pepboys and the new battery reads about 12.8v in diagnostic mode. So far the weird symptoms haven't returned since installing new battery.

 

I see your confusion. I would put both batteries on a charger and take them to your local parts store where they can check the CCA (cold cranking amps) The key is having them fully charged and afterwards with the car running with your volt meter the car should be charging at around 14 volts.
Voltage alone is not a good indication of a battery's capacity.

Think about it this way, you could put a bunch of AAA batteries in series and they could read 12 volts but they don't have the capacity to start your car. As car batteries age they loose capacity. There are other things like dead cells but I hope this helps.

 

Before leaving with a new battery, always have them test the battery voltage read out in front of you. 12.6v or greater is best, anything lower have them get another battery and then leave/install.

Measuring battery voltage when engine is on will not get the true voltage of the battery, your measuring hebcehicles voltage system.

 

There is a new generation of battery chargers designed to charge AGM batteries like the Optima yellow top.

This one was highly recommended.

http://www.amazon.com/CTEK-56-353-12-Volt-Battery-Charger/dp/B000FRLO9Y/ref=sr_1_24?ie=UTF8&qid=1515508517&sr=8-24&keywords=agm+battery+charger

 

This guy has a whole series on batteries, I have learned a lot from him.

 

A -proper- test of a automotive 12V lead-acid battery is a "load test". You can do this by simply turning on the headlamps while measuring the battery voltage. This will put about a 10 Amp load on the battery with halogens, and 5 amp with LED headlamps, with HID being somewhere between those two. If you switch to high beams the halogens will draw about 14 A. The other two types may or may not change load, depending on design (some just move the light beam).

Do note this "load test" is NOT a "starting load test" that cars other than the Prius need. BTW, CCA has no meaning for a Prius. The Prius doesn't crank the engine with the 12V battery. You should never allow someone to perform a "starting load test" on a Prius battery. They aren't designed to handle that high a current. And you should never "boost" another car from a Prius battery unless that other car is a Prius.

The voltage you see on the 12V "buss" (perhaps at the boost point) should be in the 12.5V area with the car off. With the car on (ready light on) you should see in the 14.0V area. For best results measure after the car has been sitting overnight for the first measurement (car off). The second measurement can be done anytime.

A further note is there will be some voltage drop from the battery to the fuse box in the engine compartment, probably in the area of 0.5V. For GII and GIII of course. G4 voltage drop should be much less due to the battery being in the engine compartment. Those with a "Scangauge" will see a bit more of a voltage drop in my experience, as the power must flow through yet more wiring to get to the OBDII port.

 

Google Solar BA5.

 

I disagree, a load test is a test of a batteries health. If a battery can't do what it is designed to do then it is weak or bad.

I don't know what the starting load is on a Prius and it is a lot smaller than a car with a traditional starter. A healthy battery will start a car at sub zero temperatures because it has the capacity to do so.

 

Yeah: the 12 volt doesn't crank the Prius engine, but CCA (or CA, or a few others) still are good indicators of the battery's health, and what the electronic load testers test.

 

I realize a Prius has a smaller battery because it doesn't have a high amp starter like conventional cars. You could almost get by with a large lawn tractor battery.

 

I reiterate. The CCA reading has NO meaning for a Prius. The 12V battery cranks NO engine! There are two 50 Amp 1/2 second pulses drawn from the 12V battery when you put it in "ready".
Further, the battery in the Prius IS NOT designed to "crank" an engine! DO NOT do so!

And get yourself into the 21st century!

 

So if a battery in a Prius tests as having very low CCA, well below it's spec., it's still fine?

 

Not really true.

A single very low reading under light or no load likely means it is bad.
If that is immediately after extended charging, that definitely means it is bad.

A single high reading with no load tells you virtually nothing.
But if it stays high when you apply a load, that indicates that it probably is good.

It sounds to me like his new battery never was fully charged; with no load it should read 12.7 or more and should drop only a couple of tenths in accessory mode or with headlights on.
12.3x might be OK......if it bounces back to 12.6 or greater when the load is removed.

 

I think he was trying to say exactly the opposite.

While it is true that a SINGLE CCA test on the battery immediately after charging might not mean much (ANY single test at that point), repeating the test several times over several hours certainly WILL tell you something about the battery's general health.

If it fails a properly done CCA test, then it most likely is bad.
If it passes a single CCA test, that means virtually nothing.......regardless of what application it is used in.

 

What I'm saying is the CCA test is meaningless for a Prius. It doesn't DO CCA -EVER-. The battery is not designed to do it. Read the owners manual. DON'T boost another vehicle with a Prius battery! is what it says basically.
And as I posted don't ever let anyone do a CCA test on your Prius battery! It IS NOT a "starting battery" in the automotive sense. It is a "float battery", designed to deliver a max. current of around 50 Amps, NOT over 100 Amps to crank an engine.
It should actually fail a proper CCA test anyway. Some aftermarket batteries of the same size as the Prius one can start an engine. But that is just gravy in a Prius. You don't need it.
All the Prius 12V battery has to do is supply power to boot up the computers. I suspect the two 50 Amp half second pulses I see when going to "ready" is capacitor charging. In that case the battery doesn't even have to deliver that 50 Amp pulse. It can charge the capacitors more slowly to the same effect.
It is also needed to supply power to the lights, steering, and brakes in case the car is disabled. But that again is much less than a "starter battery" has to deliver.

 

David, I've used a Solar BA5 electronic load tester on various 12 volt batteries. It's "non-intrusive" testing, and gets to the bottom of the battery's health. I appreciate the 12 volt isn't cranking the Prius, but it's still a worthwhile value for testing.