Review on LiDiVi [Upgraded Version] Dual USB Car Charger with Quick Charge 3.0, Waterproof 36W 12V USB Outlet - Fast Charging, Voltmeter & Switch for Car, Boat, Marine, ATV, Truck, and More by Bobby Blanton

The short review is that this device is accurate, easy to read and good looking with a transparent cover so you can still see the voltage by typing close the USB ports when not in use . The charging function works great and the voltage readings are accurate compared to a multimeter. I have a deep cycle/marine battery in my trailer that we use to power our LED lights, heater, water pump etc. It will not be charged. while we're camping so it's good to keep an eye on how much we're draining to make sure it lasts our entire trip. It's also nice to keep an eye on the battery while the trailer is parked in the driveway. I didn't have the guts to run the battery cable into the trailer and cut a hole to fit it properly, so I just plugged it straight into the battery in the battery box. One downside is that the ring terminals on the wires were too small to fit over the screw terminals on the battery, so I had to cut them off and crimp something larger. I believe they were 1/4 inch and I needed 5/16 inch. Aside from the nits, it works great. I love it.