I run an Antigravity ATX-30. Weighs 6lbs and has "restart technology". If the battery voltage drops below 75% it trips a breaker (there's a reset button on top). I've run it for a few years now and it still cranks just as hard as the OEM boat anchor battery (although I have a high torque mini-starter, internally regulated 90a alternator, new engine harness and good grounds).
