AndyMark, Inc. - The MK ES17-12, 12 Volt, 18 amp-hour sealed lead acid battery with nut and bolt connector has proven to be a trustworthy power source for FIRST Robotics Competition robots.
MK ES17-12S Battery 12v 18Ah Rechargeable Sealed Lead Acid | OSI Batteries
MK Battery 12-Volt Heavy-Duty Power Equipment Battery in the Power Equipment Batteries department at Lowes.com
MIGHTY MAX BATTERY ML18-12 - 12V 18AH UPS Battery Replaces 17Ah MK Battery ES17-12 ES 17-12 MAX3424381 - The Home Depot