one thing to consider is a parasitic draw test. It's a fancy way of checking if something in your car is slurping up power when it shouldn't be. Sometimes there's a component or system that's not switching off when it should, and that can drain a battery quicker than you can say "jump start."
Don't forget to scan for any fault codes too. Even if your check engine light isn't throwing a tantrum, there might be some hidden codes that could give you a clue about what's going on.
Oh, and make sure those new batteries are up to snuff. Getting them tested could rule out any issues with them.
