I used to be a tech at Ford and I used to see a lot of things because of low battery voltage or alternator issues. The lights on the dash was something I had to go though with my own CX-9 when it got a little colder at the beginning of this year. Took it to the dealership and they gave me the run around. Honestly, it was weird being on the customer end because I used to be at the back actually working on the cars. But anyway long story short, they said my battery was fine. Next morning my wife was leaving for work and all the car did was flicker all the lights on the dash, it was dead. I said screw it and just bought my own battery from Costco. It should’ve been covered under warranty but they said it was “fine” and it was only like $150 at Costco for the AGM Interstate battery and I didn’t want to deal with the dealership just to give me another mediocre battery.
The CX-9 calls for a group 35 but I was measuring and a 24F will fit with very minor modification to the battery tray. Forward of the battery tray there are two things in the way (not sure how to describe it, Lol) all you need to do is snip them off with heavy duty diagonal cutters or use a cut off wheel. It fits prefect. The AGM 24F was also cheaper than the AGM 35 so it was a no brainer, less money and more power. I love how quick it turns over in the morning in the cold.
AGM batteries benefit from being able to discharge lower and not get affected by it, they usually have a longer life span, they’re more durable and not as affected to vibrations as a flood battery and for the same group size usually have better CCA ratings.
Just thought I’d share if anyone was interested in a bigger battery option. Also good if you have accessories like a sub or a dash cam or anything more than stock.