Stupid Battery question

[bubblerboy64]

I guess the battery isn't stupid but rather its owner but I am a
little turned around on this. I have four batteries in my system
hooked in series. They are 6 volts batteries producing 12 volts
(right?) Now if I want to charge them directly (not by plugging in
the shore line of the bus) Can I disconnect the positive lead and
connect my battery charger to the bank of batteries, positive lead to
the positive terminal on the first battery and negative lead to the
negative terminal on the last battery in series? And then what do I
set the charger on 6 volts or 12 volts? Why am I doing this you
ask? I am not certain if my house charging system is working and I
want to work around it so that I know that I have a fully charged
battery bank and then drive the bus tomorrow. If the batteries stay
charged I know the bus is charging the batteries on the road. I am
trying to separate out systems so I can start to figure out my
problem. I assume the batteries are done for but if they would take
a charge directly off the charger perhaps not. And if I get new
batteries I'd like to know that the rest of the system is in order.
Any information or direction towards information would be
appreciated. Much to learn.

John Heckman
central Pa
1973 FC