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Two House Banks - AT9610283
Drawing AT9610283 shows a two house bank system. A two house bank system is less reliable than a single house bank system, and uses the batteries less efficiently. The drawing is called the Multi-Hull System, because one can argue that a two house bank system is appropriate for multi-hulls in the interest of maintaining balance if the batteries must be mounted in the two hulls.
Two Alternator Regulators
In this system, both engine/alternators are completely independent, each with a Smart Next Step Regulator. An Energy Monitor II, H2 monitors the two house banks.
Shown on the diagram are tachometers connected to the alternators. If the battery selector switch is placed in the "both" position, then the house banks will be charged in parallel by both alternators. As soon as the batteries are full enough to allow one alternator to carry the load, the other alternator will quit charging. The tachometer attached to the idle alternator will also quit operating.
To avoid an idle alternator and the loss of the tach signal, refer to drawing AT9601284 and the discussion below.
Single House Bank - AT9610284
Drawing AT9610284 is the preferred system for multi-hulls. The house bank is located in one hull, and the starter bank in the other. (Many multi-hulls allow both banks to be mounted in the aft center. Refer to AT9610285 and the discussion of Power Boat Systems below for this alternative.) One engine is started from the starter bank, while the second engine is started from the house bank.
As shown, both alternators are wired to charge the house bank. An Eliminator is used to charge the starter bank from any of the charge sources shown. Alternately, a parallel solenoid driven from the Next Step Regulator can be used to charge the starter battery from the alternator.