Review on YONHAN Quick Charge 3.0 Dual USB Charger Socket - Waterproof Power Outlet for 12V/24V Car Boat Marine ATV Bus Truck - LED Voltmeter & Wire Fuse Included - Deep Blue by Robert Aiono

This was purchased for portable and emergency fast charging of mobile phones - works great with my Samsung Galaxy S8 for example as well as any other USB powered device. The USB device is designed for use with batteries and other 12V to 24V DC power supplies. I have replaced the ring terminals with Johnson Power Pole 30A connectors for connection to ham radio power supplies in both fixed and portable to facilitate applications. The device has an LED display of the input voltage from the power supply. This gives good information on how your power supply handles the charging load. I'm likely to notice voltage fluctuations in response to fast charge mode. So the charge voltage gives you an idea of the state of charge if you know what to look for in your gear. Most basic power supplies don't have built-in voltmeters, so this one adds a feature. The construction is practical and durable, and although I bought it for portable and emergency use, it could find use in everyday workplace use.