Here is an ESC at Kershaw, 20 cell capacity!!
http://www.kershawdesigns.com/
Tekin 420F Speed Controller High amperage/High cell count brushed motor speed controller. BEC Equipped.
Forward only. Still serviced by Tekin. Includes heat sinks and instruction manual.
Size; 1.4"x1.7"x.6"
Resist .001 Ohm
Current 400 amps
Cells 6-20 cells
$79.99