{"id":1145,"date":"2025-03-27T12:16:00","date_gmt":"2025-03-27T11:16:00","guid":{"rendered":"https:\/\/dev-site.se\/sutars.com\/?page_id=1145"},"modified":"2026-05-15T10:01:13","modified_gmt":"2026-05-15T08:01:13","slug":"in-depth-study","status":"publish","type":"page","link":"https:\/\/sutars.com\/en\/wired-inspired\/cable-sizing\/in-depth-study\/","title":{"rendered":"In-depth study"},"content":{"rendered":"\t\t
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In-depth study<\/h1>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Home<\/a> \/<\/span> Page<\/span><\/div>\t\t<\/div>\n\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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Ohm\u2019s law<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Skyllermarks has, throughout the years, informed you as a boat owner about what you can gain by taking care of your electrical system. We often talk about what you should do and what you get, but not why it actually works. We are going to review some high school physics for anyone wondering why you can get double charging.<\/p>

Very briefly, we can refer everything to Ohm\u2019s law, but without further explanation, no one becomes any happier from that.<\/p>

Ohm\u2019s law describes how the current (I) varies with an applied voltage (U) and the resistance (R) over which the voltage is applied. Double the voltage gives double the current if the resistance is unchanged. Double the resistance gives half the current if the voltage is constant.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Practical Electrical Handling in Boats<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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It is a common misconception that charging in a boat takes place at 14.4 volts. Because if we look at the charging circuit, we see the following:<\/p>

The battery, as is well known, has its own voltage, a counter\u2011voltage. Counter\u2011voltage is the voltage the battery shows if we measure it just after switching off the engine. The battery\u2019s counter\u2011voltage cancels out a large part of the generator\u2019s voltage, so we are actually left with approximately 14.2 \u2013 12.5 = 1.7 V. We therefore have 1.7 volts available. That is as much as a flashlight battery, yet we still want to get fifty amperes!

The maximum UG is determined by the generator\u2019s regulator (usually 14.1\u201314.4 V), and U is determined by the state of charge of the battery.<\/p>

If UG \u2013 UB are fixed values, then we must ensure that the battery\u2019s internal resistance (RB) is low. If RB is low, the battery is said to have good charge acceptance. The battery\u2019s resistance is determined by its chemical and physical construction. A starter battery has very good charge acceptance, a leisure battery somewhat poorer, and a GEL battery has the poorest acceptance.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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No ideal circuit\n<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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The above reasoning assumes that all energy is transferred without loss from the generator to the battery, which of course is not the case. In practice, we must introduce a resistance, RK, which represents the resistance in cables, connections, isolator diodes, and similar components.<\/p>

Assume that we have a situation where the generator is at its maximum of 14.2 V. It is still charging at 50 A, and the battery is half full and provides a counter\u2011voltage of 12.8 V. The net voltage that overcomes the battery\u2019s RB is then 1.4 V. If the resistance in cables and connections, RK, causes a voltage drop of 0.7 V, then only half of that\u20140.7 volts\u2014remains.<\/p>

This is not an unreasonable assumption. Our measurements show that a standard isolator diode on its own can add a voltage drop of 0.7 volts. Add some losses in cables and connections, and it becomes clear that both the charging voltage and, in turn, the charging current can be more than halved.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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More tips & tricks<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Home \/ Page Ohm\u2019s law Skyllermarks has, throughout the years, informed you as a boat owner about what you can gain by taking care of your electrical system. We often talk about what you should do and what you get, but not why it actually works. We are going to review some high school physics […]<\/p>\n","protected":false},"author":3,"featured_media":0,"parent":535,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"_acf_changed":false,"_seopress_robots_primary_cat":"","_seopress_titles_title":"In-depth | Cable dimensioning | Sutars AB","_seopress_titles_desc":"Skyllermarks has always provided information about what you as a boat owner can get if you look after your electrical system. Here we go into more detail. Read more here!","_seopress_robots_index":"","editor_notices":[],"footnotes":""},"Pagecategories":[63],"class_list":{"0":"post-1145","1":"page","2":"type-page","3":"status-publish","5":"Pagecategories-kabeldimensionering"},"acf":[],"meta_box":[],"_links":{"self":[{"href":"https:\/\/sutars.com\/en\/wp-json\/wp\/v2\/pages\/1145","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/sutars.com\/en\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/sutars.com\/en\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/sutars.com\/en\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/sutars.com\/en\/wp-json\/wp\/v2\/comments?post=1145"}],"version-history":[{"count":12,"href":"https:\/\/sutars.com\/en\/wp-json\/wp\/v2\/pages\/1145\/revisions"}],"predecessor-version":[{"id":15598,"href":"https:\/\/sutars.com\/en\/wp-json\/wp\/v2\/pages\/1145\/revisions\/15598"}],"up":[{"embeddable":true,"href":"https:\/\/sutars.com\/en\/wp-json\/wp\/v2\/pages\/535"}],"wp:attachment":[{"href":"https:\/\/sutars.com\/en\/wp-json\/wp\/v2\/media?parent=1145"}],"wp:term":[{"taxonomy":"Pagecategories","embeddable":true,"href":"https:\/\/sutars.com\/en\/wp-json\/wp\/v2\/Pagecategories?post=1145"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}