Trouble configuring the battery charger module

So, I’ve got this battery charging control module that I'm using as an add-on to my charger
The module is an XH-M601
Basically, its job is to kick the charger on when the voltage drops below a certain point—say, 12.0V—and then shut everything off once it hits 13.8V
I’ve been scouring the web looking for some decent documentation or instructions on how this thing actually works, but I just can't seem to get the settings right.
I feel like I'm missing something obvious here—is it possible I'm supposed to be wiring the module in parallel with the charger? I'm really not sure myself.
I’ll try to upload some photos in a bit, so if anyone could give me a hand, I'd really appreciate it.

It isn't just a parallel connection; it’s wired in series. That blue block you see there is actually a relay with a normally closed contact, which keeps the charger energized by default. Do be careful when dealing with the 120V mains voltage. The parallel sensing line runs to the battery so the circuit can accurately monitor the voltage levels.



By using a small screwdriver to adjust the multi-turn potentiometers, labeled RP1 and RP2, you can delicately fine-tune the relay's switching thresholds.

In my estimation, it would have been far more sensible to simply pick up an all-in-one charger from a place like Walmart or Target... costing roughly $50, and you wouldn't have to worry about short circuits or reversed polarity, plus you'd get a built-in voltmeter.