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Sierra BS11040 Voltage Sensitive Relay 12V 125A Battery Combiner

Manufacturer

Sierra

<h3>Sierra: Six Decades of Marine Aftermarket Excellence</h3><p><strong>Sierra</strong> has spent nearly 60 years earning its reputation as one of the most trusted names in the marine aftermarket industry. Originally focused on engine and drive components for boats, the brand has grown into a comprehensive source for nearly everything a boater needs to keep their vessel running at its best — from precision instrumentation to complete engine rebuild hardware.</p><p>Now operating as a brand of Dometic, Sierra manages global aftermarket distribution from a 300,000 sq. ft. facility in Litchfield, Illinois. The Sierra brand today encompasses not only its flagship marine parts line but also well-established marine names like Shields and Moeller, offering boaters a broader catalog than ever before. Whether you own an outboard, inboard, or sterndrive, Sierra's engineering team designs products to meet or exceed OEM specifications.</p><h3>Precision Instrumentation You Can Trust on the Water</h3><p>One of Sierra's most recognized product areas is its marine instrumentation lineup. The brand's <a href="/7570-sierra-gauge-set-1480">gauge sets</a> cover everything from classic analog instrument clusters to advanced digital multi-function displays. Sierra offers packages suited to outboards, sterndrives, and gasoline-powered inboards, with options ranging from coordinated analog kits in styles like Arctic, Eclipse, and Amega to modern touchscreen solutions like the R3 multi-function gauge. Features such as scratch-resistant domed glass lenses, silicone-dampened pointers, and perimeter backlighting make these instruments highly readable in all conditions.</p><p>Behind every accurate gauge reading is a properly calibrated sending circuit. Sierra's <a href="/7570-sierra-gauge-resistor-47908">gauge resistors</a> are a critical part of that chain, ensuring the signals from sensors and sending units are correctly interpreted by your instruments. These components are built to marine-grade standards to resist moisture, vibration, and corrosion — the realities of life on the water.</p><h3>Engine Internals Built to OEM Standards</h3><p>Sierra's history in marine power is perhaps best demonstrated by its deep catalog of engine components. The brand's <a href="/7570-sierra-engine-gasket-set-5404">engine gasket sets</a> cover a wide range of outboard and inboard applications and are engineered to deliver reliable seals in the demanding thermal and chemical environment of a marine engine. For boaters performing seasonal overhauls, top-end rebuilds, or full engine restorations, Sierra gasket kits are a go-to resource trusted by professional marine technicians and DIY boaters alike.</p><h3>A Complete Marine Parts Partner</h3><p>Beyond instrumentation and engine internals, Sierra's catalog spans fuel systems, electrical supplies, steering components, shore power, and more — all covered by what the brand calls an industry-leading warranty. Sierra also maintains a comprehensive parts-finder tool that enables cross-referencing with OEM part numbers from major manufacturers including Mercury, Yamaha, Suzuki, Volvo Penta, and others, making it straightforward to find the right replacement part for virtually any application.</p>

Part Number

BS11040
09/12/2036 7:48 AM
Sale Price

$80.86

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Product Details

The Sierra BS11040 Voltage Sensitive Relay is an intelligent battery management solution designed to automatically combine and isolate dual battery systems in marine, RV, and powersports applications. This relay eliminates the voltage drop associated with traditional diode-based battery isolators while protecting your starting battery from being drained by accessory loads.

Key Features:

  • Automatic battery combining at 13.3VDC when charging, isolation at 12.8VDC when not charging
  • 125A continuous current rating with 140A intermittent capacity
  • Zero voltage drop operation—maintains full charging voltage to both batteries unlike diode isolators (0.6V drop)
  • 12VDC nominal voltage operation
  • Low power consumption: 10mA standby, 330mA when engaged, 0mA in storage mode
  • Durable glass fiber reinforced nylon enclosure for harsh marine and outdoor environments

This voltage sensitive relay automatically monitors battery voltage and connects batteries when the alternator or charger is running, allowing both batteries to charge simultaneously. When charging stops, it isolates the batteries to ensure your starting battery remains fully charged. Ideal for boats, RVs, and vehicles with dual battery systems requiring reliable auxiliary power without compromising starting capability.

good

Very good prices for quality parts!

real fine

kwik and easy

Order process is VERY user friendly!

Good rate and price

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