[Shop-talk] Which diodes for a battery charger?

[Mark J Bradakis]

 >  Also - are there positive and negative orientations to the diodes in
 >  there bow? They're not marked, and if their polarity is related to 
label orientation,
 > then one pair is mounted with both oriented the same direction, while 
the pair on
 > the other lead are oriented opposite each other.

Are you familiar with a circuit diagram for a diode bridge?  Most likely 
that
is what you are looking at here.

mjb.