Anchor Windlass and Bow Thruster Power

Powering the Bow Thruster and Anchor Windlass

Bow thrusters and electric anchor windlasses require instant high current when operating. Rather than run large thick cables back to the battery bank we opted to install a small battery bank forward underneath the V-berth. The bank provides 24 VDC with to 12 VDC starter batteries wired in series.

Keeping It Charged

Now, how to keep the batteries charged? I had originally ran three conductor AC wiring up forward with the intention of providing a dedicated AC charger. The charger would have to run off inverter when not on the dock. Instead, a Masterbus 24V/24V charger was installed connected to the nearby power distribution node on the forward starboard side, behind the forward head. This turned out to be a much easier install, and it provides monitoring of the battery bank on the Masterbus system information devices.

Two Group 27 Starter Batteries

Mastervolt Magic 24/24 Charger with Masterbus serial interface.

Switching the Bow Battery Bank

ABYC recommends there be a master switch to disconnect high current loads, such as the bow thruster or anchor windlass, when not in use. Nobody wants to be pulling up the v-berth to get at any manual switch when getting ready to dock or anchor. To solve this problem, a remote controlled battery solenoid switch was installed inline with the positive leg of the battery bank. This includes a remote momentary button that actuates a solenoid which throws the double throw switch to either the on or off position. This is an improvement over a plain manual switch, but a small wire would need to run the length of the boat, just to locate a convenient switch. It would be ideal have the ability to throw this switch using the masterbus system where a switch could be placed almost anywhere.

Bow battery bank remote controlled solenoid switch.

Sure, no problem. Well one problem is the remote battery solenoid switch is momentary. Masterbus does not have provision for ‘momentary on.’ A little creative circuitry is required to instead have Master bus control a single throw, double pole relay with each pole providing 24V when engaged. Add to each pole, a timer circuit that provides the DC output for a couple seconds, with each timer output connected to one side the original wired momentary switch (one for ON, one for OFF). When masterbus engages ON, the ‘on’ side of the relay energizes, starting the timer, effectively depressing the ‘on’ side of the manual switch. The timer expires after a couple seconds, voltage is removed, effectively releasing the ‘on’ side of the switch, and the battery solenoid remains in the on position. Similarly, when masterbus engages OFF, the ‘off’ side energizes in a similar fashion, but depressing/releasing the OFF side of the momentary switch, throwing the battery solenoid into the off position.

Dual timer momentary switch actuated by Masterbus. A little bulky, but it works.

Simple, right? It works like a charm. Now the bow battery bank can be turned on/off by any switch or event in the Masterbus system. There will probably be a switch at the nav station and/or the helm.

Parts used for this system


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