Review on ⚡ Powerful Dual QC3.0 USB Car Charger Adapter with Fast Charging & Voltage Display - Compatible with iPhone 11/11 Pro/XR/XS/8, Note 9/Galaxy S10/S9 by Andrew Dinelli

I plugged this into the cigarette lighter of one of my cars. With the engine off, it read 12.2 volts, indicating a poorly charged battery. This surprised me, so I pulled out a multimeter and checked the battery - 12.65v. I did the same with my other car. This item displays 12.1V; The multimeter showed 12.6V. Finally, I have a similar cell (from a different manufacturer) so I tested both batteries with it. This gave much more accurate readings (12.6V and 12.5V respectively). I suppose I could keep it and just add 0.4V to each reading. but instead I give it back. I see another 1 star review (in Italian) that also said the reading was inaccurate.