Maine Sail wrote this, I keep reposting it:
Hitachi Alternators 101 Alternator upgrade This comes up so often on other boating forums...
basic marine electrical system help
- Thread starter Dil
- Start date
Hitachi Alternators 101 Alternator upgrade This comes up so often on other boating forums...
You're very welcome.
These might help, too, until you get Wing's or Calder's book. Better yet, get both.
Electrical Systems 101 Electrical Systems 101
Test the alternator output at the batteries, after all that is the place where it counts. With the alternator running, a voltage reading at the batteries terminals should be 13+ volts. If not getting 13V+ to verify allow the batteries to discharge some and then take another reading. You want the alternator energized. What is the size of your alternator? 35A? It should be able to handle the refrigerator and a water pump running for a few minutes at a time. No need to overtighten the belt, just to the point where it will not slip. It takes from 5 to 7 hours to recharge a battery depending on the state of discharge. Do you keep your charger on all the time? The reason I ask it is because I have seen the mistaken belief that batteries can be charged in 2 to 3 hours and that there is no need to keep the charger on after that. A recurrent charging deficit will eventually deplete a battery. As batteries approach 75% of charge the rate of acceptance diminishes. It is those last few Amps to get to 100% charge that take the longest. There is no cheating on the time required. The other part of the puzzle is the health of the batteries. Batteries that are regularly left partially charged will sulfate and suffer a loss of storage capacity and a shorter useful life.