When to replace the 12V battery?

With the battery age, and current voltage displayed, I’d replace ASAP. You could check it’s viability with an electronic load tester*, but odds are it’ll fail the test anyway.

* Solar BA9 for example, is a prosumer-level tester.

 

!4.5 V is the charging circuit in the car trying to charge a severely discharged battery and does not indicate the battery's voltage.

You need to fully charge it with an external battery charger immediately if not sooner. The longer the battery sits in a discharged state the more its longevity is damaged if it is not already past the point of no return. After the charging is complete, test the battery to confirm (or not) whether it is holding a charge, as Mendel advises above. If you are not able to charge above 12.7 V or the load tester does not pass, replace the battery.

 

With our once or twice weekly drives, our 2010 pretty much LIVES on a charger. And that’s ok: modern smart chargers you can do that, no ill effects.

 

Both the voltages are measuring the 12 volt battery. 12.7 is the sort of reading you'd expect from a battery in good shape, measured independently of the car's dash displays.

The 14.5 reading is meaningless, the car is showing you the 12 volt reading when the car is fully on (aka Ready), getting helped by the hybrid battery. Any car, hybrid or not, will show similar (high) volt reading when on.

Too: voltage alone, while better than nothing, does not tell you much about the battery's "health". An electronic load tester (like aforementioned Solar BA9) will test the battery's health: you need to connect directly to the battery posts, enter some info about the battery (battery type, Cold Cranking Amp spec), then run the test. The tester applies a load, determines the as-tested CCA, and gives a verdict. The Solar's verdicts are "pass", "pass but recharge needed" and "fail". Something to that effect.

Dealerships, and automotive retailers selling car batteries, will often have electronic load testers these days. Dealerships will likely charge 1/2 hour labour to test (for 5 minutes work...), while automotive retailers typically will do the test for free. You get more bees with honey...

Still, bottom line, with battery of 6~7 years age, depleted due to accidental drain, just replace it.

 

Got mine at 140k never changed battery. I have 276k now.

I had to jump it one time from leaving light on and was fine that was 10s of thousands of miles ago.

 

Is it the original battery? If not how old is it? What brand?

 

I don't recall I jumped it one time probably a year ago. I bought it at 140k and that was 4 years ago. It's approaching 280k miles I really got my money worth lol. I got it for about 4k in 2017...very clean with leather.

At 140k ("The Honey Moon Phase") I did new tires, front wheel bearings and struts. Did trans flush (total waste highly advise never ever ever doing that)....Spark plugs.

It only needed the front wheel bearings / tires everything else was just because it was new to me.

Since then did 1 or 2 more wheel bearings several sets of tires. And cheap struts.

No serious issues at any time ever including today.

For the last 100k miles it has had a P0456 "very small evap leak" and burns oil.

And tire pressure light is faulty the last 20 or 30k miles.

Have seriously done nothing from 200 to 280k. Can tell needs front sway bar links but not urgent. Cruises along with the check engine light on and the tire pressure light on lol and has been that way 100k miles.

 

If you have time, take a look at the battery and let us know if it’s OEM or aftermarket and any date code on it.

 

With that age it could be worth replacing. If it was a brand new battery then pick up a trickle charger for about $70.

I once made a mistake and left the light on overnight, draining a brand new battery so that it wouldn't start up in the morning. In this case, I was able to fix this by putting it on a trickle charger for a few hours - there's a special mode for it to let it work for this specific type of battery. Search for Schumacher Fully Automatic Battery Charger/Maintainer.