Brand new yellowtop battery installed yesterday. This morning, battery tested at 11.4V. Not normal?

yeah, that's a bit low. often, new batteries are sold without having been charged first, which is usually necessary because they self drain sitting around.
take it back and ask them to charger, or get yourself a charger/maintainer.
alternatively, you can drive it or just leave it in ready for up to 8 hours depending on how low it is.

 

11.4v under load is not awful. You will probably be ok if you drive the car for about a week. It should charge while you're driving.

that readout on the multifunction display is not very accurate as it's measuring under load.

 

Optima are garbage batteries... Their style of quality control is recharging defective batteries and trying to sell them again. If we had decent consumer protection laws these crooks would of been shut down long ago. Get your money back and buy a real battery.

 

THIS.

BUT any new battery needs to be fully charged before being used.
Yours may not have been.

11.4 under no load.....or minimal load......is DEAD.
But you may have gotten a bad one too.

Charge it up at a low rate for 12 to 24 hours and then see how it goes.

 

Leaving it in ready for 8 hours will not do a very good job of charging the 12 volt battery or the hybrid battery. You have to drive the car.

you should have tested the battery at the counter before you bought it. Bring a DVM next time you probably have a yellowtop that sat a long time in under charged condition

You should return that battery and buy the dealer Yusa. They have come down in price.

Then go on Amazon and buy a good battery charger.

A healthy 12 volt battery lives at 12.6 in a G2.

 

Maybe.
Disconnect one side of the battery and leave the charger connected for at least 12 hours.
But it appears that your new battery isn't very healthy.
Which is not unusual for the Optima batteries lately.

 

Oh did not realize that's a charger too thought it was just a load/analyzer. if you got a charger my brother why are you running the car for 8 hours?

My last 2 yellowtops flaked out right at the end of there warranty period. 3 years almost to the day. That's after many remedial charges so i can see how its doing. The factory Yusa was always much more expensive but they have come down in price quite a bit. But i understand your predicament.

12 volt issues on a G2 are the most posted thing here now usurped by bad hybrid battery.

 

I had nothing but bad luck with the Optima Yellow Tops on my Gen2. I ended up returning it, buying a OEM Yuasa (sp?) from the Toyota Dealer and never had a problem with the resting voltage again.