Low battery voltage

[gungu]

My 19' boat has a 1996 Johnson 130 hp V4 outboard motor. The voltage of my brand new battery (660 CCA) remains 12.25 V despite several hours ( > 20) of operation. I know that the battery voltage should be at least 12.7 V.<br />What can be the culprit of this problem.<br /><br />Thanks in advance.

 

[R.Johnson]

Re: Low battery voltage

12.25 would mean that the battery is only at a 50% state of full charge, but keep in mind a volt meter is not a good indicator of battery condition. You need a load tester to tell that. Does your battery have good cranking power at this reading, or are you just concerned about this voltage reading. Your engine has a 9 amp, fully regulated system, How much equipment are you drawing off the battery? I would do a running test with an amp meter to see what is really going on. You will want a service manual to guide you through these test's. You want to be carefull doing a running test with an amp meter. If you short out a lead, you will have a charging problem.

 

[gungu]

Re: Low battery voltage

The motor is crancking well. However, my fishfinder is functioning weird and I get when transmitting on my VHF radio low voltage alarm.<br /><br />Can I use my digital V/A meter to measure the battery running voltage and amps at two different rpm's (1000 and 2000)?

 

[rickdb1boat]

Re: Low battery voltage

If you use your meter and measure the voltage across the battery when the motor is not running and then start it and measure it again with all the accesories off, it should show an increase at 2000-3000 RPM's, although it may be small. I understand what Mr. Johnson is saying about the load test, but lets at least see if the charging system is working. I believe your rectifier is fried, causing the no charge condition...