Join Date: Jan 2003
Location: Maine Coast
Thanked 303 Times in 235 Posts
Rep Power: 18
Re: Battery Charging Problems
My Interstate engine battery is one month old, my WM house is 2011 and my Napa house #2 is 2010. Output reading at the alternator is 13.7v but the readings at the batteries themselves while the engine is running is 13.1v.
Your alt is working but you have severe voltage drop in your charging circuit. It will takes days not hours to charge at 13.1V. Being an older Catalina it is likely you have an ammeter in the charging circuit. You may also have the old and dangerous alternator bracket that needs an upgrade (if it is an M-25). The ammeter needs to go to the scrap heap and the alt output re-wired with MUCH larger wire. You will also want a dedicated alt ground wire run direct to the battery bank neg bus or the bank itself..
Your batteries may also be sulfated and your battery monitor incorrectly wired. What we do know is that you need to eliminate this voltage drop or nothing will get any better. This is a well known chronic problem on many Universal & Westerbeke engines..
P.S. With everything OFF you should have a 0.0A draw except for those short instances when a bilge pump kicks on......
-Maine Sail / CS-36T
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Last edited by Maine Sail; 07-25-2013 at 09:31 AM.