What battery charger for winter storage?

X2 on the Battery Tender. Go for the Battery Tender + model, not the wall wart. The BT+ has diagnostic LEDs and two pig tails. One pig tail has clamps, the other has eyes that can be connected to battery leads for goof resistant quick hookups regardless of lighting or sobriety. I've been using them in the garage at work for a few years without any Tender or battery failures.