The OP does not give any info on his truck or how the truck gets WiFi, so this is based on my experience with my GMC Canyon and getting WiFi service via the built-in OnStar system as of several years ago. GMC may have changed the system since then.
WiFi service is provided by my Canyon when the engine is running. The truck computer automatically shuts down the WiFi service approx. 30 minutes after the engine is stopped and the key is removed from the ignition (to save the battery). To keep the WiFi service running, I can remotely start my truck with the ignition key fob(?) to recharge the battery. The computer will shut down the engine after approx. 15 minutes unless the key is reinserted into the ignition. A battery tender will not keep the computer from shutting down the WiFi service.
It's a real PITA system so I get my WiFi service via my cell phone hotspot that's plugged into the TT wall socket. The only disadvantage is that the truck OnStar system has a greater reach (signal boost) than my cell phone.