Review on Battery Tender Plus 12V Charger and Maintainer | Motorcycle, ATVs, and More - 1.25 Amp Automatic PowerSports Battery Charger | 12V Battery Chargers - Model 022-0185G-DL-WH by Austin Hearshman

Installed in my mother-in-law's car as she only drives it once a month (if that). I fixed it with a screw in the engine compartment. If you have the space I would recommend two screws and some spacer to avoid vibration. The mounting holes require an #8-2" sheet metal screw for a secure fit. I also added a 120V power supply to the front of the car. This makes it easy to unplug the car (mute the plug) and drive away. https://www.amazon.com/gp/product/B07LC686S8/ I used this adapter model because it's easy to remove (although I wrapped it with silicone sealing tape).