There are a lot of good automatic tender type chargers out there today.
WalMart carries Schumacher (sp?) and they have worked good for me.
A "trickle charger" won't do but there is no need to spend a lot of money either.
A good one can be had for less than $30; often around $20.
And concerning yourself with temperature compensation on a small battery tender is just being silly. EXACTLY where you connect the clips isn't important either.
I have no power near mine when stored so I run truck and generator once a month and move it 6 inches or so.