Product: Daygreen 36V 48V to 12V 13.8V 30A 414W Car Step Down Power Voltage Regulator Multifunction DC DC Converter Acc Switch, Non-Isolated
Brand: Daygreen
 
Wiring: ACC to Switch, INPUT+ to BAT+, INPUT- to BAT-, OUTPUT+ to LOAD+, OUTPUT- to LOAD-. If no need the ACC function, then use clamp insert ACC and INPUT+ 
Reminder: Never reverse the polarity. Use the enough big cable to avoid the voltage drop. Never connect to solar panel or wind turbine. Never charge the battery. Keep good air convection. 

Daygreen P/N: A4D13R8C30 
Efficiency: 96% 
Input Voltage: 30-60VDC 
Output Voltage: 13.8VDC 
Output Current: 30A 
Ripple: 200mVp 
Line Regulation: ±0.2% 
Load Regulation: ±0.2% 
Voltage Accuracy: ±1.5% 
Enclosures: IP68 
Dimension: 160*113*35mm 
Net Weight: 1kg 
Case Operating Temperature: -40~85°C 
Certificates: CE Rohs 
Warranty: 3 years 
MTBF: 100,000 hours 
 
Application: 
36V/48VDC battery of vehicles as input power to 12VDC appliances as output load. 

Questions:
Why some people perfers to 13.8V? 
There is voltage drop due to cables or old battery, then 13.8V is perfect to work for your 12V load as the car audio or other loads will get enough voltage to run.

What is ACC?
ACC works as a switch when your vehicles have ACC to avoid battery drains.

How to choose the correct current for loads? 
For example, if the max current of your load device is 10A, then choose 10A/0.7=14.28A at least for resistive loads according to international standard. 
If the load device is motor or compressor, then you may choose 10A/0.5=20A according to real testing result since the motor and compressor starting current may be 2-3 times than nominal current.
100% full rated power and stable output voltage
100% burn-in test and 4 times quality inspection
Over current protection, Over voltage protection, Over temperature shutdown, Fuse built
Aluminium shell with epoxy potting and waterproof IP68
3 years warranty and 15 years lifetime ACC function

Search query: 12 to 48 volt conversion
Relevance: Exact