Yeah, it's a switch capable of decent amperage, to allow/disallow power to flow from one side to the other. Follow the wires to find out what's what.
Example amazon product page: https://smile.amazon.com/Ampper-Battery-Disconnect-Isolator-Vehicle/dp/B07413JWLD/
Yea I think i just killed my 2 year old trailer battery by letting it draw down so many times. Finally bought this:
https://smile.amazon.com/gp/product/B07413JWLD/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
This took literally 5 mins to install and will be a life safer. Just screw it into your battery box.
Also bought a solar panel kit so i can ensure its always 100% topped off.
When I started camping like this, i always made sure to charge the battery before going. Sometimes you forget a USB plug is drawing power, etc. You might want to to install one of these between the battery and the fuse box if it doesn't have one already.
Ampper Battery Switch, 12-48 V Battery Power Cut Master Switch Disconnect Isolator for Car, Vehicle, RV and Boat (On/Off) https://www.amazon.com/dp/B07413JWLD/ref=cm_sw_r_cp_apip_1BGtGsX2HV6yw
I used this and broke the black/negative terminal. Mounted to side of battery box for easy access.
Worked great this FL winter while it was in storage for 2-3mo.
I bought the following and attached it to the battery box. There are several instructions on the internet on how. The instructions for the device said to attach it to the negative side.
https://www.amazon.com/dp/B07413JWLD/ref=cm_sw_r_cp_apa_i_U8jnFbRCSMSVA
Really depends on your budget and what you are trying to monitor. The Victron bvm712 is what I went with.
The Display comes with a premade cable. If it's not long enough, you can make or have a longer one made from cat5 cable.
It's really just a multimeter with a remote screen. This particular one has Bluetooth so you can read it from an app and review history.
Basically the shunt is a two terminals side by side. It measures the current following through it so all devices must run through it to get measured. If measuring consumption, ALL of your negatives run through this. If I remember correctly basically everything you would run to your battery negative goes to one side of the shunt and the chassis ground to the other. Or it's everything that consuming power (fan, inverter, lights, fridge, etc) negative to one side and battery to the other with battery ground to the chassis.
Electrical system is a complex as you want it to be. If it's your first time, if recommend following and existing plan like this (the best and easiest to understand I've seen) where someone has already calculated your wiring gauges, fuse size, battery size, inverter, etc. Just be sure to understand the limitations of your system AND your capabilities. Next to gas, it's potentially the most dangerous element of your build.
https://www.parkedinparadise.com/solar-calculator/#100W-wiring-diagram
If you need cutoff switches try local Marine store. Amazon has these:
Ampper Battery Switch, 12-48V Battery Power Cut On/Off Master Switch Disconnect Isolator for Car, Vehicle, RV and Boat https://www.amazon.com/dp/B07413JWLD/ref=cm_sw_r_cp_apa_i_BavuCbG3166AT
Make your life simple. Install this on the top of your battery case. Easy peasy. Battery Disconnect
On my truck I have a different winch, but I only had to trim about a dime size piece of material off the radiator bracket. It was super easy. I then just repainted it with some good primer and paint.
On my friends truck, I installed the same winch you have. We relocated the entire solenoid control unit to mount it in front of the radiator on two 1/8th inch steel bars. Those bars are bolted onto the two painted cross members located in front of the radiator. There are already holes in those paint (body matched) cross members. I only had to drill in one other spot. It is a pretty good solution that was easy to make by hand. Let me know if you would like a pic of his setup, and I can get it to you tomorrow.
The main thing you want to keep in mind is access. You want your access to the power button, free spool handle and the connection for the wired controller to be as close to the top of the truck as possible, otherwise you will be doing gymnastics every time you want to use it.
Personally, my first choice would be to mount it traditionally with the winch up-write. That'll leave you trimming a little sheet metal, but that bar that you have to trim is not a piece that carries much (if any) of a load. In other words, it isn't going to weaken any of your structure.
My second choice would be to relocate the solenoid, removing it from the winch and mounting it in front of the radiator and those 2 painted cross bars. When it is mounted in this location, have the power switch and cable connection point facing up for easy access.
Finally, I would highly recommend adding a 12V switch to the main power going to the winch. I was surprised to see that the Smitty winch didn't come with one. If you don't install one, your winch will be potentially ON all the time, and the entire power cable will be hot all the time. IMHO, this is a fire hazard if you are ever in a front end collision. I would (and did) install one of these as close to the battery as possible to make the whole thing a bit safer. https://www.amazon.com/Ampper-Battery-Disconnect-Isolator-Vehicle/dp/B07413JWLD/ref=sr_1_4?crid=3OJER98YZETA7&keywords=12v+battery+shut+off+switch&qid=1660449902&sprefix=12+v+battery+shut%2Caps%2C121&sr=8-4
With that switch, you will never have to worry about a parricide draw from the winch, it reduces your risk of fire, and it makes future maintenance a bit easier. Just my 2 cents.
That would work well.
There's also the low-tech version
Turn on when vehicle is running, turn off when vehicle is off.