Thanks for the info so far!
I'll have to read through those PDF that @Ian.M as they look promising.

Just to clarify on what I'm doing... When I charge a battery, the markings on the battery have a current limit such as 2.1A for example. I normally short my power supply output and set the current to that value. I then remove the short and set the voltage to 13.8 for example, and then connect the battery. If I didn't have a diode in series causing a voltage drop, the power supply would send current into the battery to charge at 2.1A (if the battery was very low) and then as the battery was charging up the power supply would switch out of CC mode and then would go into CV mode. This is all automatic in the power supply.
So, I'm a little confused by the circuit @MarkF posted because it has a resistor to set the current. Maybe I'm not understanding how it's supposed to work? I figured I would still set the current and voltage using my power supply and the circuit would just prevent current from flowing backwards while eliminating the voltage drop so that the power supply could regulate current and voltage correctly at the battery terminals. Hope that makes sense.
(Also, does anyone know how to properly link to a username on these forums? "@" doesn't seem to work.)