My Sailboat Doesn't Start After Sitting for One Week. How Can I Tell If the Batteries Are Still Good?

Question:

My Catalina 28 had trouble starting last weekend. I think you did an Electrical Audit on the boat 4 or 5 years ago when I installed new AGMs. The boat is not connected to shore power often and I motor probably 2 to 3 hours a day and on battery the rest. I realize the batteries are old and I will be checking the connections. It doesn't start after sitting for a week. Is there another way to check if the batteries are good? Voltage is OK. I think amps are there problem. Any hints would be appreciated. - Tim

Answer:

To troubleshoot a starting battery, you want to measure voltage at the starter battery and at the starter solenoid. With a multimeter, take a measurement of the voltage at both of these locations without the starter solenoid being engaged and while the starter solenoid is engaged. In total that is 4 different readings. These readings will tell you if there is excessive voltage drop under load when the starter solenoid is engaged. - Jeff