Sorting out wiring, need help

[in.vivo]

I've been slowly piecing together a small home battery system, mostly for backup during outages but also because I like tinkering with this stuff lol. Over the last year, I picked up a stack of LiFePO4 cells, a decent BMS, and even scored a used inverter from a neighbor who was upgrading his solar. Everything has been sitting in the garage, and now I'm finally at the point where it's time to run some real wiring.
Here's where I'm second guessing myself because I've watched a ton of Youtube builds, but everyone seems to have their own way of wiring things, for me I'm trying to balance safety, neatness, and cost. My main questions are around cable gauge, breaker placement, and whether I should run shunts in line for monitoring right from the start or just keep it simple until I expand.
I'd really like to set it up clean and future proof, not something I'll regret redoing in six months. Anyone else here been through this stage and found a wiring setup that made life easier for you?

 

[Opt123]

Interesting project!!
You're right to be thinking through the wiring now. I also hate it if I have to redo anything so soon!
I think you'd want to oversize your cable gauge.
Look at your inverter and BMS specs for max continuous current.
A 5kW system often uses 2/0 or 4/0 AWG for the main battery-to-inverter runs to be safe.
It's better to spend a little more on thicker cable than risk a fire.
The breaker placement is critical, so I suggest putting a main breaker or fuse as close to the positive battery terminal as possible.
This protects the entire system and is non-negotiable for safety.
And yes for the shunts, definitely install one from the start! You'll thank yourself later.
Having real-time data on your State of Charge and current flow is invaluable for monitoring and troubleshooting.
It's much easier to put it in now than to try and retrofit it later.

 

[Riseee32]

I’d say start with heavier gauge cable than you think you’ll need, it saves headaches later if you expand