I know that a car’s charging system is not designed to act as a battery charger. It is designed to maintain the battery while the battery operates the starter, lights and etc. But, every time you start a car, there is a large amperage drain on the battery. If you continue to start your car many times a day and if the charging system is not putting somewhat of a positive charge back into the battery, then the battery will eventually go dead. So would it not make sense that if you have a dead battery and you jump start the car and run it for a long time, some charge would be put back into the battery? Then if you drive it a lot every day, more and more charge would be put back until it is eventually charged?
My mechanic tells me that the battery would not fully charge by itself, with just the charging system. That doesn’t make sense to me because the charging system doesn’t know whether the battery was fully discharged ot whether it just lost some charge due to starting. Therefore, wouldn’t it keep putting a charge into the battery as long as you run the car and would that not eventually charge the battery even if it takes a long time?