I have a SetPower fridge/cooler (same design as many others on the market) that runs on 12v-24v DC. Saw new models on the market that were battery powered and figured 'why not upgrade my existing cooler!'.
The DC-DC converter is set to constant voltage output of 12.5 with low volt cutout set to 11.8 and a small adjustable low volt audible alarm board I set to 11.5 as battery protection, in the sense that it screams at you "hey stupid, change batteries!" Searching articles has shown test results detailing makita 18v batt BMS are designed to shut the tool off around 11v and under low amp draw, go as low as 9v before shutdown. So I'm playing safe with my settings so as not to push a battery to the point where the BMS shuts the battery off completely where it can never be charged again.
Pretty cool converter though, it will show you how long its been running, how many watt/hrs, amp/hrs, and what amps its pushing. You can use all this info to set output limits too. Anyway here is the parts i used:
DC/DC Converter: https://www.amazon.com/dp/B098347BD9?psc=1&ref=ppx_yo2ov_dt_b_product_details
Power cord to fridge: https://www.amazon.com/dp/B0BVK99CVZ?psc=1&ref=ppx_yo2ov_dt_b_product_details
Makita Battery Adapter: https://www.amazon.com/gp/product/B0B8NRSN88/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Low Volt Alarm Board: https://www.amazon.com/dp/B07XM7YL4N?psc=1&ref=ppx_yo2ov_dt_b_product_details
NOTE: to set up the low volt board you can wire it to the output of the converter, set converter to 11.5v (or whatever volts you want it to alarm at) then turn the POT on the low volt board till it alarms, and your set.
Screws: Some sheet metal screws i had laying around, but I made the holes small enough you can use a wide range of diameters and just drill out the holes to accommodate.
Happy Camping!