John Langford's electrical upgrade discussed two options to improve the cruising capabilities of the Catalina 320. The first and least pricey was to modify the existing alternator to remove the internal regulator and add a smart" external regulator. This provided the boat with a nominal 160 amp-hour capability, assuming the second 4-D battery was dedicated to starting the engine and not used as a house battery. In actuality you then have between 50 and 80 amp hours available depending on how charged your house battery is and its "health". He also installed an ammeter/amp-hour meter to have the ability to determine the charging amperage to his batteries and the amp-hours lost while on the house bank at anchor or at a dock without shore power.
Roy Kraft, #187, "Sea Wings"
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