[Cddelta]

Group 35 is fine... Northstar Grouo 35 AGM is an incredible battery. You could also do a Group 24F (F is important means the terminals are correct for this application).

I plan to upgrade to a Northstar Group 24F AGM, but I’ll have to modify the battery tray and tie down set up... but the cranking capacity is almost double.

Don’t be too worried about the “start stop” capabilities of the Subaru factory battery... it’s a sub par battery that is better than a normal flooded lead acid, but not as expensive as AGM. It’s undersized for the job, in my opionion. Keeping the battery lightweight and inexpensive keeps manufacturing costs down.

 

[Cddelta]

I was wondering if you did that 24F upgrade. I've been searching for some DIY instructions on how to do this, but am not seeing anything yet. My OEM battery went dead after 1 hour of everything off except the radio, so I am looking for the best option.

Yes, I upgraded to the 24F. No need to change battery cables or connections. The OEM battery tie down bracket works just fine. The plastic sleeve around the original battery is not necessary, nor is the plastic tray. In its place, I cut a piece of rubber for the 24F battery to sit atop. Be careful when swapping the negative battery posts… it’s actually a current sensor and is easily damaged… I made the mistake of over tightening the negative terminal and ruined the sensor, which was over $100 to replace.