I purchased my O'Day 28 3 years ago and don't know how old the batteries are. One will not hold a charge and the other passes the load test. I'm planning to replace both in the spring. The dead one died on a day I made liberal use of my new Raymarine EV100 autopilot. I also had my IPhone and a small wireless speaker plugged in. Does anyone know how long I should be able to run that equipment and still start the engine?