Focus on the:

Schumacher SC-600A SpeedCharge High Frequency Battery Charger

This Features

• Fully automatated process with 4 settings
• A 6 amp medium charge monitors the battery condition.  It will adjusts charge rate downward to prevent battery damage
• 4 amp medium charge has self-adjusting charge rate ideal for everyday charging needs and keeping your battery in peak condition
• 2 amp slow charge for charging small batteries 
• 50 amp clamps for top and side-mounted battery posts

Tech specs

• Input Voltage: 120V AC
• Output Voltage: 6V/12VDC
• Output Power: 2A/4A/6A continuous
• Amperage Control: Push-button
• Warranty: 5 Year
• Dimensions: 6.9" x 3" x 7.5"
• Weight: 2.1lbs

You can find much more about trickle chargers at the link