The charging action itself also keeps the battery temp at a good
level. I have done this on bad nights when I knew the temp. in the
garage would be too low -- got good results even without a battery blanket.

 > 
 > i just connected the leads of the charger right to the cable clamp bolts,
 > ran the leads outside the battery box thru an indentation in the box i'd
 > made for the battery blanket cord.  plugged the charger into a flat, HD
 > extension cord i have running from the 110v outlet inside the cabinet under
 > the sink over to the battery box.  was pleased as punch.  i plug in the van,
 > the battery warms and charges.
O.K., This is very close to what I did, except I left my multi-tester
in series in the circuit, measuring the Amps flowing through, and
hoping that the 6 amp fuse I put inside the multitester would blow in
case of something going wrong and the battery charger beginning to fry things.

 > 
 > then i thought "i wonder how much leakage the charger diodes have" as they
 > are made to be connected only when it is plugged in to 110v.  measuring the
 > reverse current going back into the charger, the diodes allowed about 3 mA
 > leakage.  not much but it bothered me.  so i unhooked the charger :(  
 > 
It is probably the reverse current in the power transistor inside your
charger (same difference :-).  3mA is not bad -- considering your
battery is capable of holding a charge of 50 to 100 amp-hours, you'll
be wasting .006% to .003% or so of your total available charge every hour, or
about 2% to 1% of the battery charge every four days -- remember to 'plug'
your car in if you'll be gone for too long :-)

The Radio Shack store on my way to work does carry 10 amp diodes.
Careful: a 10-amp Silicon Diode (as opposed to a Germanium diode,
which has higher reverse current) will dissipate about 7 watts at full
throttle (10 amps).  means it needs a heat sink so it does not form a
health hazard.  I'd just keep the charger use it the way it is -- 3mA
is about the order of the current drawn by the clock and/or the radio
when it is turned off (newer radios that remember things).
Cetin