See full version: How to Test a Marine Battery
Press and hold the button in the center of the rotary dial of the multimeter and turn the multimeter on. Continue to hold the button in the center of the dial for two seconds, putting the meter into the "Automatic Touch Hold Mode."
3/8- and 5/16-inch wrenches, box- or open-end
Open the boat's battery box. Use a 5/16-inch box- or open-end wrench to remove the black ground cable from the battery's negative post. more
One of the last things you do before the beginning of the boating season is make sure your boat's starting and deep-cycle batteries are fully charged. They were fully charged at the end of the previous season, before you sent your boat into its winter hibernation and the battery charger won't overcharge them, but how did they hold up over the winter? If you check your battery regularly -- every other week, whether you're boating or not -- you may learn something about your battery's condition. more
Insert the red probe into the terminal on the face of the multimeter for volts, ohms and diode testing, marked with the letter "V" and the Greek letter omega, the symbol for ohms. Insert the black probe into the common terminal marked, "COM." Turn the selector dial on the face of the multimeter to the "V DC" function for measuring DC volts. here
Touch the red probe to the positive post of the battery and the black probe to the negative post of the battery. The meter will beep and display the battery voltage on the screen. For a wet cell battery, the reading should be 12.4 volts or higher. For an AGM or Gel-Cell battery, the multimeter should show 12.8 to 12.9 volts; a voltage reading of 10.5 volts or lower indicates a battery cell has shorted out. more
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It often seems that after running the merc for a good hour or two, the battery (charged up before running and fairly new) will read 12.5 V (or a bit less) instead of the 12.65 V that would linger after a good overnite trickle and a few hours to come down from the 13+V of the charger.
The only thing I understand (and can locate on my own) is a test of the battery voltage while the motor is running. I will do this. If it is easy to locate the other test points, I would appreciate a description of where to put the V meter leads. more
Re: How to test if motor is charging battery?
Aside from the obvious, "are the batteries dead?" lol. How do I know if my boat battery charger is bad?
The easiest way to check is with a voltmeter. Make sure the charger is plugged into a working outlet and grab your multimeter or voltmeter. Turn the charger on and touch the probes onto the battery charger leads. Make sure the meter is set to DC, then look at the amount of volts your charger is supposed to be producing. If your meter is reading less, chances are you may need to have your charger looked at or even replaced. Mine reads 13.2 v when charging. more
A couple DIY steps to test your marine battery charger. You'll need a multimeter. Plug the charger into shore power. Turn the multimeter on and switch it to the DC setting. Stick the red multimeter probe on the red wire (+) from the charger, stick the black lead to the negative (-) or black side. Your batteries are automatically going to give you a number of somewhere between 12.7-13.3 if they have a charge. Then you'll want to turn on the charger. If that DC voltage number on the multimeter rises any, your charger is good. If it does'nt change, its time to change the charger.