Referencing Post #9 and Post #13, Toyota and Lexus Hybrids do not have an alternator.
The Motor Generator #1 attached to the Infernal Internal Combustion engine creates the
charge for the High Voltage Battery and also the 12v battery. This is why we should not
ever use our Hybrids to jump start a conventional IC car.

 

This supports that Hybrid 12V batteries may not be AGM since there is not as much strain on them.

 

I think some of lexus hybrids like the prius do or did have agm from what I have heard. Sure the software is different to handle the agm.

 

The original battery on my 2019 300h was a standard one, actually neat since it's a white almost translucent plastic, so you can see the fluid in it (albeit once you take it out of the car).
Then I replaced it with an AGM.

 

Did you notice any difference in mpg with the change.

 

No, why would I?
It's such a tiny drain compared to the rest of the power levels in the hybrid system.

 

In 2020 when I bought my car there were posts of loosing 1 to 2 mpg by not putting in correct battery. Have not seen that for several years now.

 

Hmm... interesting. I reached out to a buddy who runs an Optima agm in the wife's Oddysey, 4 years no issues. I have a 6 y/o agm in my air cooled Porsche and no issues FWIW.

 

Good to know and could be why posts like that did not continue. They were saying internal resistance and other factors were cause. The hybrid charging system is nothing like an alternator. I can go on a 200 mile trip with alternator and battery fully charged and with hybrid nowhere near.