Keep in mind that alternators are intended to provide a maintenance type charge, not a deep cycle charge.
In a way thats true.....
If you let a battery go "dead" to say below 11 volts or so, you can charge it back up but it will cause problmes holding a charge. If an Alternator wont charge a battery back up after its dead from age or being dry, neither will a Charger. I work on buses where we have a fleet of 300 buses. When we come across a "dead bus" that wont start, we change out the batterys. If the old ones were allowed to go "dry" adding water and charging them only works about 20% of the time. If they are installed back in a bus, within a week they will be dead again. The main reason for using a battery charger is to maintain a battery. People get in their car in the winter time and "click, click, click", the battery is dead. They pull it out and put it on a charger. They put it back in the car, and within a few days, "click, click, click". Dead again. When a battery goes dead on its own from age, or not being maintained, charging it up does no good at all. Alternators now doa fantastic job of charging. Generators were different. When we get new batterys in we are supposed to "charge them" to bring them up since they only have a "static" charge. Sometimes we dont have time so we throw them in the bus, get it to start ( or jump it ) and let the alternator charge them. Never had a problem. Alternators now put out some decent amperage, and thats what charges the batterys, the amperage thats applied to them at a given voltage.
