Verified answer

Your detail reminded me of the identical problem I had - with a brand new car and battery. After many trips to dealer it turned-out to be a loose post in the battery .. .. no one suspected a battery because it was brand new but it would make intermittent disconnect then quickly be AOK with a jump or short charge.

Disconnect a battery cable overnight. Does the battery still drain overnight? If yes, it has internal problems and is draining itself. Old batteries do this.

If not, you need an ammeter and go looking for the problem.

-Engine overhaul mechanic and electrical system expert, since 1972

Could be a loose post inside the battery. I had one that would start a vehicle one time and then not the next. I was trying to crank it and it wouldn't crank, and then all of a sudden when the connection to the post was made in the battery, the hydrogen ignited and blew the top off of the battery and blew acid all over. Be careful with it. Connect a volt meter directly to the battery posts and watch it while the charger is on it.

Disconnect the alternator from the battery overnight and see if it starts. A bad diode in the alternator can drain the battery.

With putting a six amp charger on for only ten minutes I'd say the battery is not draining dead overnight. You have a battery connection problem like dirty cables on the battery or at the other end of the battery cables, like the terminal at the starter or the ground. You may also want to make sure the ground cable has contact between the engine and the frame.

Have your battery tested. If it's more than 5 years old, it's probably time to replace it.

Make sure that the brake light switch is not stuck on or an interior light that stays on (in glove box or elsewhere). And of course make sure that the battery connectors and posts are clean. Get a volt meter and check if battery voltage in the morning is more than 12v before trying to start it. If that is good maybe there is an intermittent problem with ignition switch or starter solenoid.