Mounting Aux battery in back of 2021 Bronco

[James Hunt]

Where and how did you mount it out of the way? Just talking a 100Ah lithium that I'm going to use for as house battery.

 

[smritte]

Google is your friend here. When you figure it out, also design where your going to put the charge controller. All of these things have a large footprint.
You may even consider a couple of smaller batteries. As much room as my Cruiser has, I don't have room in the back for another battery. I ran a large single in the front until recently, Now I run dual up front.

Edit. Looks like no one has successfully built a dual battery set up that I could find and rear battery mounts are not there either. Most have gone to a Jackery or equivalent.

See how much room you have behind your rear panels. You may be able to mount four 25ah batteries. I have a whole electrical panel and compressor behind one side in my Cruiser. Another option is building a drawer system or storage cabinet.