Battery test

[David S.]

When I recently pulled the batteries(deep cell 24's) off my 90 C-30 I noticed a few drops off liquid in the bottom of the battery box. I have no idea on the age of the batteries, but one has a tag which appears to indicate 1998, but its difficult to tell because of the condition of the tag. We only had the boat in the water for about a month and the batteries seemed ok.  Long winded but what is the best way to test the batteries to determine their condition and whether or not to replace. And if replacement is necessary what batteries are the best??( On mooring, no shore power!!) Thanks as always. David

 

[Rob R.]

Okay, I'll take a stab....

Hi David, I am no electrical guru, but I would fully charge the batteries and then let them sit (disconnected from your electrical systems) for about a day. When you go back the battery, hook your mulitmeter up to it and check the voltage. It should be around 12.7 to 12.75 when fully charged (to be really accurate, you will need to perform a load test (see link below)).If your battery sits much below 12.5 after charging it and load testing it, I'd consider having a professional service the battery, or just replace it.A half discharged battery will give around 12.4 volts, and a fully discharged bat will give 12.0 or less.For best maintenance, you should charge the battery after each usage. This will keep the battery from suffering sulfation, which shortens the length of the battery's life. For more info, please see the link below. Best Regards, Robp.s. - let us know how you make out!

 

[Larry W.]

Battery testing

David; Battery tests are different for house use and engine starting and you should have two separate systems. As a general rule, your house battery should be able to sustain a 5 amp load for 20 hours, and your engine start battery should be able to crank your engine, with the stop lever pulled out so the engine does not start, for 30 seconds. These are generalities. Also, a hydrometer will give you another indication. Get the big West Marine catalog, they have a good battery primer in there.

 

[David]

Thank you!!

Thanks for your help. I charged the batteries and also load tested them. They seem to be ok. This spring I intend to parallel the two house batteries and install a starting battery under the aft berth.

 

[Rob R.]

Great Configuration....

Mine is similar. Make sure you get a good sailboat electrical manual to guide you through the process - one that explains the differences between parrallel, series, etc... and also one that talks about isolators, combiners, and all that fun stuff. Best of luck!Rob