What to check before 12 v battery replacement?

you can get a free load test at most auto parts stores. if you're getting the triangle, you should really have the trouble codes read. a new 12v to replace one of unknown age and 12.5 max is not a complete waste of money, as long as your willing to spend whatever it takes to fix it if the 12v isn't the issue.
i like the oem, but there's nothing wrong with buying the cheapest one you can find either.

since you're getting 14.8 volts from the inverter charging system, that tells me it's trying hard to keep the 12v charged without much success.
you might also have a parasitic drain when the car is off.

 

Generally speaking when you have warning lights being displayed on the dash there are OBD2 codes being stored in the ECUs (computers), how long has the RTD been making an appearance, and was that the only warning light being displayed?

Next time the RTD appears find a hybrid compatible OBD2 scanner (many chain auto parts store will offer free scans, or a friendly mechanic may scan it for free) and retrieve the stored codes (DTCs), then post them here for additional guidance. Realize that the 'free scan' may not be compatible or able to retrieve the stored DTCs. Disconnecting the 12v will erase the stored codes (DTCs) and prevent you from knowing what might be wrong with the vehicle. Always record or write down the codes before disconnecting the 12v battery.

You can take the 12v to a local auto parts chain for a free test. The OEM 12v from the toyota dealer may be price competitive with the offerings from the auto part stores, and likely of higher quality. I would avoid the Optima. Some members here use wheelchair batteries.

FYI : you're moderated until you've posted 5 times.

 

It is normal for the charging voltage to drop some after the car runs for a while.

It is NOT normal for a battery with no load to lose anywhere near that much voltage overnight.
You NEED a new battery. You don't need to "check" anything else.

Any "name brand" exact replacement should be fine.
Optima had a run of reliability problems a couple of years ago but I think they are past that now.

 

Depends on your DIY attitude. How many miles are currently on the vehicle, and is the HV battery an untouched original?

Not the codes (DTCs) or readings that you've offered above.

Again, not the reported DTCs above. It would need to be pretty low for that too happen, and it still wouldn't throw those DTCs.

Did you need the repair manual workups for the above DTCs, or can you find them yourself? (FYI : P3009 is AKA P0AA6)

Given the reported DTCs, and assuming that you have some time, you may want to tear into the pack and check the HV battery ecu and voltage sense wires for corrosion. While in the general area you could also inspect or clean the HV battery fan as well.

 

Where are you in South Carolina?

Take a look on Techstream Hybrid Control System tab. Look for the "ShortWave Highest value. What does it show? This is a measurement of the quality of isolation between the HV system and the car chassis. Perfect is 5.0v. I normally see 4.99v on cars in good condition. Anything less than that means you are having an issue develop. I think once it hits around 3.2 (?) it triggers the isolation fault code. The vast majority of times, this code is due to HV battery electrolyte leakage making a path to the battery case.

A good way to test your blocks voltages is after the car has sat overnight or longer. With your foot NOT on the brake, press the power button 2 times. This will allow you to go online with the car with the engine not starting and not charging the battery. Then look at voltages with TS and you'll be able to see them 'as-is'. It usually makes it quite clear which blocks are a problem. You may not have anything completely obvious, since all you have is a P0A80 and not a code for a specific block yet. The computer knows something is going on, but just hasn't figured out exactly where.

 

That battery should fall on its face in a load test optima has no bearing at this point that battery should be holding 12 5 12 7 overnight easily easily so I don't think you have to spend 250 bucks AGM batteries in that size and whatnot can be had for in the 140 range if you look carefully I like DEkA getting hard to find I have an advance auto gold AGM in my 09 I think

SM-A715F ?

 

For the 12 volt battery, you can assess it's condition with one of the electronic load testers. I'm using a Solar BA5; think the latest similar iteration is BA9:

https://cloreautomotive.com/product/ba9/

Ancel BA101 looks good too.

Both are around $70 CDN for me (through Amazon), so maybe $40~50 USD in the States?

 

Stop grasping and replace the 12 V battery which is unquestionably worn out.......and then see what you are left with.
OR....just sell or trade it in as is.

 

When it drops to 12.15 overnight with no load.......there is no need to do any additional testing.

 

occam's razor

 

I bought my BA5 close to 10 years back now (speculating a bit), and have used it on various batteries, on various cars, thinking long-haul.

 

I just have a fluke 116 meter and a few chargers with diagnostic modes .

SM-A715F ?

 

Yes, it is a good piece of equipment, no doubt.
But sometimes it just is not necessary.

 

Was probably easy to sell in this market.

 

BUT.....not worth the design effort.
When the time comes that "cells" start going bad, the rest of them usually follow fairly soon.
Most owners won't appreciate having to change a few cells every couple of months no matter how easy it is.

The people posting in places like this who seem to enjoy tinkering with their hybrid batteries are a TINY minority among all hybrid owners.
Indeed, a really LOT of owners don't even understand how a "simple" 12 V battery works.