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Upgrading the DC Charging System (a bit lengthy likely boring)-gctid396239

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  • 2850Bounty
    Not boring at all, and nice work, but this thread may better serve the guys if posted in the Motoryachts section.

    Leave a comment:

  • Upgrading the DC Charging System (a bit lengthy likely boring)-gctid396239

    Our 1999 480 DB came from the factory with a pretty typical factory setup with two 8D batteries. Port battery is used for "Cabin Main", some running gear and port engine start. Starboard battery is used for running gear, electronics and starboard engine start. They include an "emergency start" switch to parallel the (2) 8D batteries for starting the port engine after you have run down the port battery from house use. Not a very satisfactory system for a 48 foot boat with 12 volt starters on 6V92TA Detroits. Both alternators were connected to a battery isolator with two alternator inputs and two battery bank outputs. Factory alternators are the gear driven Leece-Neville 90 amp units supplied to Detroit Diesel.

    The previous owner added a 2500 watt Trace inverter with (6) L16 golf cart batteries which was fine but our experience was the engine alternators did a poor job of charging the inverter bank. Little wonder, since whoever did the install took the original port battery connection, ganged it to the starboard battery and connected the inverter bank to the original port battery feed. In essence, the inverter bank replaced the port battery and the original port and starboard batteries were permanently paralleled. This served to confuse the isolator which resulted in a voltage loss of about 1.5 volts on the output side. Diode based isolators typically lose .75 volts between input and output. Also strange was having the inverter bank starting the port engine. Here is the original isolator:

    Our solution was based on the following approach:

    1. Dedicate the port alternator to the inverter bank with no intervening isolator, hence no voltage loss.

    2. Run the "Cabin Main" circuit off the inverter bank rather than the port battery.

    3. Install a 180 amp, digital switching isolator with one alternator input and three battery bank outputs. These isolators have one of outputs as a priority charging bank, say for engine start. The main advantage though is that there is zero voltage loss from input to output.

    For those interested in such stuff, here is the proposed setup:

    Note that a control switch was added to the port alternator, for the connection to inverter bank and the "Cabin Main" circuit.

    Here is the revised DC main panel under the flybridge stairs:

    Here is the ProMariner digital switching 180 amp isolator:

    Note that all battery feeds and the incoming alternator feed need to be fused. This makes things a little crowded on the panel.

    The alternator feed:

    The resulting system seems to work well, with the port alternator dedicated to the inverter bank which also serves as the house battery. The starboard alternator now charges (at full voltage) the port and starboard batteries (now dedicated to running gear and engine starting) and the third output goes to the genset battery (previously not charged by the mains).

    ProMariner offers quite a variety of isolators but here is the unit we used:

    The ProMariner unit shows you exactly what is happening with an LED dedicated to each output bank. A key on ignition 12 volt circuit activates the isolator when the starboard engine is running. A future option would be to replace the port alternator with a high amperage unit but only if needed. The Leece-Neville gear driven alternators retail for $2700.