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Passage Maker - - Electronics -

ith two state­rooms, each with their own heads, a full gal­ley and a com­fort­able sa­lon, the fuel ef­fi­cient sin­gle diesel en­gine Back Cove 41 may be the per­fect long range cruis­ing yacht. This in­no­va­tive in­te­rior and deck plan will en­hance your days on the wa­ter with com­fort­able seat­ing and clear views of your sur­round­ings.

boat unat­tended at a ma­rina is that the shore­power could get dis­con­nected, un­plugged, the breaker may trip, or a va­ri­ety of other mishaps could leave the boat un­pow­ered and drain the house bat­ter­ies. This is bad for the bat­ter­ies and might re­sult in other prob­lems such as spoiled freezer food. We want the sys­tem to ride through a shore­power fault by fail­ing over to the gen­er­a­tor, run­ning it if needed to save the bat­ter­ies, and re­turn­ing au­to­mat­i­cally to shore­power if the genset came back.

POWER FIXES

I’ll start with the equip­ment we in­stalled and how the dif­fer­ent com­po­nents work to­gether to solve the re­quire­ments we have item­ized above.

The first step—and the most im­por­tant part of the de­sign—was to in­stall a 240V, 60Hz in­verter. This is the most im­por­tant part of the de­sign. In­stall a suf­fi­ciently large in­verter sys­tem such that all ap­pli­ances in the boat can be run off the in­verter. On Dirona, we have a 4kW in­verter to feed the 110V ap­pli­ances, so 6kW is suf­fi­cient to sup­port the 240V equip­ment we have on board. In our case, we in­stalled two par­al­leled Vic­tron 3kW, 110V in­vert­ers to achieve 6kW of 240V power. We par­tic­u­larly like this in­verter choice be­cause they are sim­ple and don’t in­clude a charger—all they can do is in­vert—and are ca­pa­ble of de­liv­er­ing far more than their spec­i­fi­ca­tion. The in­vert­ers are spec­i­fied to de­liver 6kW at 240V, which is roughly 25A, but they can de­liver peak loads over 50A and can op­er­ate for ex­tended pe­ri­ods at or even be­yond their rated out­put with­out sag, over-tem­per­a­ture, or cut­ting out. They are tanks, and just keep de­liv­er­ing no mat­ter what. I’m amazed to re­port they can start the SCUBA com­pres­sor, where the re­quired in­rush cur­rent at startup can ex­ceed 50A.

Af­ter a year of use, we con­tinue to love th­ese units. The key to mak­ing this de­sign work is to en­sure that the in­verter ca­pac­ity is suf­fi­cient to run the boat with­out re­stric­tion, us­ing what­ever com­bi­na­tion of 240V equip­ment you need.

So, if you choose to du­pli­cate this de­sign, en­sure you have ad­e­quate in­verter ca­pac­ity. 6kW is enough for us but you can get 240V in­vert­ers in a va­ri­ety of sizes up to 20kW. And if your boat is 60Hz, you’ll need a 240V split-phase in­verter—some ap­pli­ances need that neu­tral con­nec­tion.

The next log­i­cal step was to re­place the ship’s ser­vice selec­tor switch which, as de­liv­ered on Dirona, (left­most of the three in the open­ing im­age) al­lows the op­er­a­tor to feed the 240V breaker panel from ei­ther shore­power or the gen­er­a­tor. We re­placed this new switch with one that adds sup­port for a third in­put so we can feed the 240V panel and all 240V ap­pli­ances on the boat from shore­power, gen­er­a­tor, or in­verter. This third po­si­tion runs the en­tire house sys­tem off the new 240V in­verter.

The third step is the switch­ing. As de­liv­ered, the bat­tery charg­ers on Dirona draw power from the 240V panel. In other words, one of the 240V “ap­pli­ances” serves as the two bat­tery charg­ers. It would be a very bad con­fig­u­ra­tion to be run­ning the 240V ap­pli­ances off the in­verter and have the bat­tery charg­ers tak­ing power from the in­verter, us­ing it to charge the bat­ter­ies, which are then feed­ing the in­verter. How­ever, to sup­port many of the use cases above, the charg­ers must be pow­ered sep­a­rately from the 240V panel. We want, for ex­am­ple, the 240V panel to be run­ning off the in­verter while the charg­ers are run­ning off shore­power. So, we sep­a­rated the bat­tery charg­ers from the 240V panel and added a charger ser­vice switch to sup­ply the charg­ers from ei­ther shore­power or the gen­er­a­tor.

An elec­tri­cal di­a­gram show­ing th­ese first three mod­i­fi­ca­tions is shown op­po­site.

The fi­nal com­po­nent upgrade to com­plete the sys­tem was to re­place the 85A start bat­tery charger with a 190A at 24V al­ter­na­tor and in­stalling heav­ier ca­bling for this larger al­ter­na­tor. The house bat­tery bank al­ready has a 190A at 24V al­ter­na­tor so, in this new con­fig­u­ra­tion, we have two 190A at 24V al­ter­na­tors on the main en­gine. With the two al­ter­na­tors in ag­gre­gate, we have 9kW of power gen­er­a­tion on the main en­gine. But, you prob­a­bly won­der why we would ever want a 190A charger on the start bat­tery sys­tem since the orig­i­nal 85A al­ter­na­tor was ar­guably al­ready far more than would ever be re­quired.

Well, it turns out that big­ger is not re­ally a prob­lem in that a large al­ter­na­tor with a high qual­ity smart reg­u­la­tor can pro­duce what­ever the start bat­ter­ies need re­gard­less of how low. So, hav­ing an ex­tra-large al­ter­na­tor does no harm but is also

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