probably the starter
Disconnect the positive battery cable and charge it with a slow charger. Clean and reconnect the cable once the battery is fully charged.
something is causing a drain on the battery when switch is turned off
Something is on draining the battery or it has a dead cell and needs replacing.
Dead cell in battery or something is on pulling power from the battery. Disconnect the negative battery cable overnight with the battery fully charged (12.6 volts). If the battery is dead the next morning it has a dead cell and needs replacing. If however the battery is still fully charged then a light is on somewhere or a relay is stuck closed.
Not too sure of your question. But correct or not will depend on the sentence. The battery is charged. = correct.
No. They are charged the same way.
A fully charged battery should read approx. 12.8 volts without engine running With engine running should read approx. 13.8-14.2 volts
It arcs because something is on when you installed the battery. Can be a light, or relay sticking.
Then something is on pulling power from the battery. Any light on the vehicle or any relay that is stuck closed.
Defective alternator, dead cell in battery, something on pulling power from the battery when the vehicle is idle, corroded battery cable connections, or loose alternator drive belt.
Yes. A battery can be charged while in the vehicle.
ATP is like a charged battery