{"product_id":"enerdrive-b-621-120-sp","title":"Balmar 12V 120A 621 Series Alternator, Single Foot Mount, Isolated Ground (No Pulley)","description":"\u003ch2\u003eHigh-Output 12V 120A 621 Series Alternator for Marine and Mobile Power\u003c\/h2\u003e\u003cp\u003eEngineered to meet the electrical loads of modern vessels and off-grid setups, this \u003cstrong\u003e621 Series 12V 120A alternator\u003c\/strong\u003e provides reliable, high-output power generation. Unlike standard automotive units designed only for intermittent starting battery top-ups, this high-output alternator is built to recharge deep-cycle house battery banks. Balmar designs its 6-Series alternators for recreational applications and describes them as ideal for modest charging upgrades.\u003c\/p\u003e\u003cp\u003eWith a substantial \u003cstrong\u003e120A output at 12V\u003c\/strong\u003e, it significantly reduces engine run times required for battery charging, saving fuel and minimising engine wear. Whether you are upgrading a marine auxiliary engine or outfitting a specialised mobile workspace, this unit delivers the charging performance your house battery bank needs.\u003c\/p\u003e\u003ch3\u003eIsolated Ground Architecture for Enhanced Safety\u003c\/h3\u003e\u003cp\u003eA critical feature of this 621 Series alternator is its \u003cstrong\u003eIsolated Ground (IsoGrd)\u003c\/strong\u003e design. Standard alternators use the metal casing as the negative return path through the engine block. In marine environments—particularly on aluminium, steel, or timber vessels—ground return through the engine and hull can lead to severe stray current corrosion and galvanic damage.\u003c\/p\u003e\u003cp\u003eBy isolating the negative terminal from the alternator chassis, this unit ensures that all return current travels safely back to the battery bank via dedicated cabling. This architecture drastically reduces the risk of electrolysis in marine applications and protects sensitive onboard electronics from ground loop interference.\u003c\/p\u003e\u003ch3\u003eKey Features and Benefits\u003c\/h3\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eHigh-Output 120A Capacity:\u003c\/strong\u003e Delivers rapid, dependable charging for large 12V deep-cycle AGM, Gel, or Lithium (LiFePO4) battery banks when paired with appropriate regulation.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eIsolated Ground (IsoGrd) Design:\u003c\/strong\u003e Prevents stray current corrosion and galvanic damage by isolating the electrical ground from the engine block and chassis.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eSingle Foot Mounting:\u003c\/strong\u003e Suits 1in (Approx. 25.4mm) Motorola-style or 2in (Approx. 50.8mm) Delco-style single foot (SingleFT) brackets. Balmar lists the 1in Motorola-style mount as typical for Westerbeke, Lehman, Hino and Pathfinder engines, and the 2in Delco-style mount as typical for Volvo Penta, John Deere, Perkins, Mercruiser and other GM-based engines.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eCustomisable Drive Setup:\u003c\/strong\u003e Supplied without a pulley (suits 17mm bore pulleys), allowing you to match the exact belt profile and ratio required for your specific engine configuration.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eDual Fan Cooling:\u003c\/strong\u003e Compact, small-case 6-Series design with dual fan cooling and a high airflow frame.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003ePulley Compatibility and Exclusions\u003c\/h3\u003e\u003cp\u003ePlease note that this alternator is \u003cstrong\u003esupplied without a pulley\u003c\/strong\u003e to accommodate varying engine belt configurations. To complete your installation, select the appropriate pulley for your drive belt system from the compatible options below (each featuring a 17mm bore):\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eB-61-0020:\u003c\/strong\u003e Dual V Pulley, 2.7in (Approx. 68.6mm) x 1\/2in (Approx. 12.7mm) Deep V, 17mm Bore\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eB-61-0070:\u003c\/strong\u003e K-6 Serpentine 6-Rib Pulley, 2.45in (Approx. 62.2mm), 17mm Bore\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eB-1310:\u003c\/strong\u003e K-8 Serpentine 8-Rib Pulley, 2.4in (Approx. 61mm), 17mm Bore, Short (STD)\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eIdeal Applications\u003c\/h3\u003e\u003cp\u003eUpgrading to a dedicated high-output, isolated ground alternator helps solve the common problem of chronic battery undercharging. It suits:\u003c\/p\u003e\u003cul\u003e\n\u003cli\u003e\n\u003cstrong\u003eMarine Vessels:\u003c\/strong\u003e Yachts and cruisers requiring isolated ground systems to help prevent hull and propeller corrosion.\u003c\/li\u003e\n\u003cli\u003e\n\u003cstrong\u003eRVs and Expedition Vehicles:\u003c\/strong\u003e Rapidly replenishing auxiliary battery banks during transit.\u003c\/li\u003e\n\u003c\/ul\u003e\u003ch3\u003eUpgrade Your Charging System\u003c\/h3\u003e\u003cp\u003eEnsure your vessel or vehicle has the dependable charging capacity it needs for extended off-grid operation. Select your compatible 17mm bore pulley and add the 621 Series 12V 120A Alternator to your system today for reliable, isolated-ground power generation.\u003c\/p\u003e","brand":"Balmar","offers":[{"title":"Default Title","offer_id":43631393701949,"sku":"B-621-120-SP","price":1300.38,"currency_code":"AUD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0602\/3918\/3933\/files\/balmar-621-series-120a-12v-alternator-b-621-120-sp.png?v=1792490561","url":"https:\/\/www.solar4rvs.com.au\/products\/enerdrive-b-621-120-sp","provider":"Solar 4 RVs","version":"1.0","type":"link"}