When the bow thruster was installed, two 100 amp lithium batteries were located under the V-berth. These batteries were also used to power the new windlass. The batteries under the V-berth were connected to the house battery bank in the engine room via a Victron Orion DC-DC charger. This approach has the advantage of requiring smaller gauge wire (4 gauge) and the different chemistries of the V-berth (lithium) and the engine room (coiled AGM) are made compatible via the DC-DC charger. During passages (when the bow thruster and windlass are not used), it would be nice to use the batteries at the bow as a rainy day fund for the house batteries. Unfortunately, DC-DC chargers are uni-directional. To solve this problem, a second DC-DC charger was installed. However, there is a problem in that both DC-DC chargers cannot run at the same time (or they would fight with one another. To solve this problem, I used the remote on-off connection on the DC-DC-charger. While the switches on the two chargers could be linked in several ways, I chose to use a STDP (single-pole double-throw) switch connected via the “low” pins on the DC-DC chargers.
The second DC-DC charger was located under the V-berth with the other charger.
The SPDT switch was located in the engine room. Switching it to the right moves energy from the V-berth to the house batteries and switching to the left moves energy from the house bank to the V-berth.
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