Smoker,
Your "Battery Bug" in the cabin sounds more like a voltage monitor. I use a monitor in all my newer cars that don't have a dash ammeter. They plug into a cigarette lighter. Simplest and cheapest is the Harbor Freight one, which has LED's to monitor the battery off (~12.6 V is good) and the alternator when running (~14.3 V). Another I have is an Eqquis (Amazon) that gives the exact voltage. My "Battery Brain" is different. It isolates the battery if it senses the voltage too low, so you will always have enough left to start the car. Even though its relay is rated ~200A, I don't run the starter current thru it.