Originally Posted by Quique
. . . I noticed my batteries are not grounded. do they needto be grounded to the engine?. . .
I agree, there is some basic 12VDC background needed here. The "The 12 Volt Boater's Handbook" can probably be found in used boat parts
stores or libraries.
Direct current works by electrical
energy, commonly stored in batteries, leaving one terminal of the battery
and going to the "load/motor/whatever" and then back again to the battery's other terminal. As was stated by MaineSail if your engine starter operates your battery (at least the engine starting battery) is connected (grounded) to the engine block. The only exception to this would be if your engine starter had two (2) thick battery cables
attached to it, one black, one red - instead of the normal one red cable.
Same thing goes for the engine alternator
which makes DC power from the rotation of engine and sends it via one red cable to charge your battery. It normally does not have a separate black (negative) cable attached so it is using the engine block as the negative (ground).
If you have more than one battery bank then it is normal practice for all the negative cables from the various battery banks to be hooked together usually at a "amp-hour" meter shunt and then the other end of the shunt is connected to the engine block and/or the boat's negative battery bus terminal.
So by definition everything in the boat's DC system is "grounded" to a common point usually the engine. There was another discussion awhile back about using seawater grounding plates for the DC system. Normally this is taken care of by the engine being connected metal to metal with the transmission
and the transmission
connected to the propeller
shaft and propeller
which is "in the water
Some instruments or lighting
fixtures that have metal cases or frames should have internal or external connections from the DC negative system to the metal case or frame. This is done more to protect from an electrical
short and fire than human electrical shock hazards. 12VDC and 24VDC systems really don't have enough energy to "shock" a normal human. However, AC system do have enough to give your anywhere from a tingle to a heart stopping zap. So making sure the "safety ground" system on the boat's AC systems is in good condition and each AC load and generation item has a safety
ground unless it is rated as "double insulated."