Trickle charge will make perfect sense in a car that does not get regular use, and the discharge from the battery is greater than the charge from a short run. A car sitting in a garage will still discharge because for example, the alarm on, the clock is still running, and the engine ECU will be taking a current. That is a fact. Then chances are you start the car, the a/c is on, heated screen kicks in, etc..... and unless you do a decent run, the battery will never be recharged to the level it was before you cranked the engine (which is an enormous load, especially in an auto, as you cannot disengaged the gearbox by depressing a clutch, when u start). In most modern cars ( like last 20 yrs) if the amps are to low, the pre starter solenoid will not activate, and prevent the car from starting. Welcome to the joys of modern cars with advanced electrical systems.