Thursday, August 22, 2013
Week of Aug 5, 2013: alternator and battery charger
This past week I worked on a sailboat with a bad alternator and a boat with battery/ charger issues. The sailboat with the bad alternator wasn't putting out any charging voltage. Turns out that the stock hitachi alternator was internally regulated so I had to get a new one no matter if it was the alternator or the regulator that was bad. I learned how to match an alternator to the batteries that it will be charging. A good rule of thumb is get an alternator that is 25% the capacity in amp hours of you batteries. The customer I had had 400 amp hours of capacity so I matched it with a 100 amp alternator. I learned what exactly the Amp hour rating means. For my customers two 8d agm batteries the amp hour capacity was 400 @ 20 hrs. That means these two batteries can handle a 20 amp load every hour for 20 hours. Really cool to find this out. I also diagnosed a bank of two house batteries to be bad and also found that his shore power charger wasn't working which I believe killed his batteries. You can see I pulled the charger apart to find a small piece that was the size of a nickel wrapped in heat shrink with two leads broken off the circuit board. Great week!