[metroschultz]

It sounds as if your alternator is dying. A slow and painful death.

No disrespect Coyote, but, Do Not disconnect the battery to check your alternator output.
Bad JooJoo
Any car made after 1989 with on-board diagnostics can (not always, but why risk it) Burn the computer internals when you disconnect the battery while the engine is running.
Both of the cars you have listed that are ICE have weak (not electrically tolerant ) computers.

I would spring for a new (re-manufactured) Alternator.

Pull the battery and put it on charge while you replace the alt.
It is not a difficult task on either of your cars. ( I don't remember if you told us which car)
If you don't have a load tester then carry your battery to the corner gas station and ask him to test it for you, after it has charged.
I do not put much faith in the Big Box Auto Stores. They are usually nice people, but they don't have real world experience. IMHO
Anybody can read an instruction pamphlet, but not everybody knows what they are looking at when it comes to resultant data.
The local shop should Help you and they can also intelligently install your battery or cover the warranty if need be.
If you have a shop you have been dealing with over the years, let them help you. Tell them you need to do the repairs yourself for monetary reasons and offer to give them some sort of compensation,(not necessarily money) ("I'll bring you some of my wifes killer brownies next batch")
for their efforts.

BTW (Open offer to ALL Ecomodders) if you find a car within 100 miles of 23452 let me know and i can go look at it for you.(may have to wait til Sat) Most vehicles in this area have very little rust on them. If it is cheap enough i will go ahead and pick it up. You will have to get it from here though.

Let us know how this turns out.
S.