Technical article from Blue Sea Systems
January 18, 2008
Five reasons to use a remote battery switch were presented in the October newsletter: increased safety, lower cost, reduced weight, lower voltage drop, and added convenience. As an example of cost savings, placing a remote battery switch near the battery bank, and placing the control switch in a convenient location can easily eliminate 20 feet of high current carrying DC circuit wire. The cost savings at typical retail prices can be approximately $400 for 4/0 wire, $275 for 1/0 wire. Technical Brief: Five Reasons to Use a Remote Battery Switch.
When choosing a remote battery switch, look for these essential features:
- Switchable under load-Typical rotary marine battery switches are not designed to switch under load. In contrast, remote battery switches are designed to switch high currents. Remote battery switches should be able to repeatedly switch high enough current to start engine(s) or switch sustained high current loads such as inverters. The components of a remote battery switch must be able to handle high current switching. In particular, the main contacts must withstand the arcing that occurs when making or breaking high current. Silver alloy contacts, as an example, are able to withstand the repeated arcing that occurs with high current switching. In contrast, bare copper contacts are subject to welding and high resistance copper buildup.
- Rugged-Battery switches are critical to the safe operation of a boat and therefore must be rugged enough to withstand rough treatment and the harsh marine environment. A remote battery switch might be installed in a place where people step on it or knock it with a heavy tool box, or it may be subjected to ocean spray. All components of a remote battery switch must be strong enough so that the switch always works in day-to-day operation, and in an emergency. The ideal remote battery switch should be one of the strongest components in the electrical system.
Manual override mechanism-A remote battery switch should have the capability to be operated manually if problems limits its electrical operation. This manual function also should be rugged. A mechanical override is likely to be used in an emergency, where there is an even greater chance for it to be subjected to rough treatment.
Terminal studs-Terminal studs should be large enough to accept and support large wires, and should be securely mounted in the assembly so that they accept sufficient torque to secure large cables. Because remote battery switches are designed to carry large currents, they may require 4/0 cable connections. The weight of 4/0 cable can break terminal studs or pull them loose from their mountings. Studs that are secured to the assembly with a nut may loosen with vibration. Studs that are swaged into the assembly are far less likely to loosen with vibration or when torque is applied to secure a cable terminal, and they are far less likely to pull out from the assembly when large cables are hanging from them.
- Draws no current in ON or OFF state-One of the biggest concerns on a boat when away from home port is a dead battery. It is desirable to avoid all unnecessary drain on batteries. Today's marine electrical systems have more and more components that draw small amounts of continuous current - for example, alarms, clocks, and circuit status indication lights. Although each individual parasitic current tends to be small, their cumulative effect can be significant. While it is difficult to eliminate all parasitic current drain, it is desirable to eliminate as many as possible. A remote battery switch should draw no current when in ON or OFF state.
Consider the benefits of using a remote battery switch. Then, look for a remote battery switch with these important features.
Original article from Blue Sea Systems