Chandlery June 2006 Issue

An (Almost) Idiot-Proof Battery Switch

The 5511E has luminescent panels on both the front and back. With 7/8-inch studs, it can accept multiple terminals and up to 4/0 AWG cables.

Last year we tested battery switches (PS June 2005) and a favorite was the Blue Sea Systems 9001e. The company recently introduced a new line of switches, among them some improved heavy-duty, four-position switches, versatile mini-switch panels, and the new Series E Dual Circuit switches, one of which PS recently examined.

Although we stand by our last test results, Blue Sea disputed some conclusions, particularly our preference for metal over plastic shafts. Blue Sea says the shaft on its switches is made of durable glass-filled Lexan polycarbonate and Duralon that was chosen to reduce heat and eliminate the chance of electrical shock that a metal shaft would present in the unlikely event that the knob breaks off. The company also pointed out that the Blue Sea switches actually offer slightly more cross-sectional area than the thick-plated BEP 721 switch, another PS favorite. Our overall impression after the last test was that the Blue Sea switch is a rugged switch that performs well under high loads. The knob suits slippery fingers well, but we aren’t convinced it’s as ergonomic as some others. We will take a closer look at the Blue Sea’s new heavy-duty switch, the HD 3000, which was introduced after our test.

Rated for 300 amps continuous and 525 amps intermittent, the 5511 Series E switch has many of the construction details found in the heavy-duty switch. Its chief purpose is to serve as a foolproof replacement for the conventional four-way (Off-1-2-Both) switch. In essence, it is a simple on-off switch with a third emergency “Combine” position (clearly marked with a yellow warning label). In the “On” position, both banks are completely isolated and connected to their dedicated loads—starter and house. Isolation not only prevents a bad house bank from discharging your start battery, but it also eliminates the risk of power spikes that might cripple sensitive electronics.

The 5511’s “Combine” position (the same as “Both” on the four-way switch) allows you to parallel both banks for starting or charging, if needed. In the “On” position, you can’t charge both banks, so a simple isolation diode (with its insipid voltage drop) or more expensive automatic charging relay (ACR) is needed to idiot-proof the switch. One feature missing is an alternator field disconnect, which protects the alternator if the switch is accidentally turned off while the engine is running. For a daysailer looking to replace an old four-position dial, the $38 5511E is an affordable way to simplify battery switching. Serious cruisers with their short-term memory intact can stick with four-position switches, which allow more manual control.

We’ll take a closer look at the 5411E switch, install it with a Blue Sea 7600 Battery Link ACR on a test boat and report any new findings. Our first take is that the 5511 is a well built switch, much like the heavy-duty version we tested. It is also fairly hard to turn, although Blue Sea says it has recently modified the design to make this easier. We suggest giving it a few twists before you leave the store.

Contact - Blue Sea Systems, 360/738-8230,

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