I have a 89 Jefferson 37 Sundeck and in my cockpit inside the helm panel which has switches for Radar, Depth Sounder, etc., there are positive and negative bus bars that power is led from.
I have a Stanley inverter that I plug into my 12v cig adapter which I use to power my laptop. My laptop has all my charts and use PolarNavy as my chartplotter. I have charts from New Jersey, Hudson River, Erie Canal, All the Great Lakes, both U.S and Canadian waters. It keeps the laptop powered up all day long. I have never had an issue with lines getting hot or pulling too much power.
At the end of the day, whether I am in a marina hooked up to shore power or on the hook and run the genny for a bit when first dropping the hook and in the AM for coffee, I make sure the laptop is charged from 110v.
Coming from the bus bar the wire is short.
The upper helm is powered by a breaker on my DC/110 electrical panel in the main salon.