If they are wired in parallel they are both charged at the same time. Basically the two batteries act like one larger battery.
for automotive purposes, you will need two 12 volts batteries connected in SERIES. That is, connect the two batteries with one cable from positive to negative. That will give you 24 volts. In order to charge both batteries with one alternator, you will need a battery equalizer
Yes if they are connected in parallel but I would not recommend it. Just charge them one at a time.
With the batteries in series, the alternator provides the same current, and therefore the same charge to all the batteries. The alternator can take no account of any current being drawn from the 12V take off point. Part of the charge current is being fed to the 12V load and not to the batteries. Therefore, the 12-24V batteries are being fully charged while the 0-12V batteries are being partially charged. Over a period of time, the difference between the charge levels will become more obvious.
50 batteries?? Are you running a competition grade sound system?? Here's my two cents. Chances are, you alternator was designed to charge a single battery. Making it charge 50 at once will likely kill the alternator. However, if you don't hook up your extra batteries to the alternator, they obviously won't get charged. If you will be remotely charging the batteries, (say at home in the garage) then I guess that won't be a problem. But if you do want to charge them while the car is running you'll probably have to set up a special charging rig, or at least a much stronger alternator.
If the car is a 12 volt system, then you will want to connect the batteries in "parallel". IE: negative to negative and positive to positive. Because of "cranking amps" it would be advisable to use a cutoff switch when starting the car. (The switch would interrupt the power from one of the batteries so the amperage wouldn't toast the starter) Also, the alternator should be isolated as to charge the batteries one at a time.
The two batteries can be wired in series BUT unless they are identical batteries in an identical state of charge they should be checked regularly to see if one of them is fully charged (the voltage has risen to 14.5 volts).
They were both free of charge.
They were both free of charge.
No you cannot.
You need to multiply the number of coulombs by the number of volts. If the two batteries are in series, then you can add the voltage of both batteries.
No, but you can charge each one individually without separating them from the series loop.
If the clubwagon was designed to act as a camper, then 2 batteries are installed. 1 battery is to power accessories in the camper, the other is to supply power for the starting and operation of the vehicle. They are hooked together in sequence so the alternator can charge both as you are driving.