Quick Charge MB1210x6
Charges up to six 12V batteries simultaneously @ 10A each (or you can combine terminals for more amperage).
Charging profile can be programmed individually for each battery via DIP switch (several profiles available for flooded, AGM and Gel batteries).
Works fine, last used three weeks ago. One of the six controllers was replaced a few years ago with a newer version, it does not affect functionality (LED could blink at a different rate under certain conditions).
Located in Severna Park, Maryland (near Baltimore/Annapolis/DC).
Sells new for $675 plus shipping.