# Marine Dual Purpose Batteries > Marine dual-purpose batteries: engine starting and on-board service power in one battery. AGM by Fullriver, Varta, Exide and Kronobat. 24h dispatch. **Category:** [Start](https://baterias.com/gb/beginning) → [Batteries](https://baterias.com/gb/batteries) → [Starter Batteries](https://baterias.com/gb/starter-batteries) → [Boat Batteries](https://baterias.com/gb/boat-batteries) - **Canonical URL**: https://baterias.com/gb/marine-dual-purpose-batteries - **Language**: en-GB ## Description **Marine dual-purpose batteries** combine **engine starting** and **on-board service power** in a single block: navigation electronics, fish finder, lights, fridge or windlass. They are the practical choice for boats with limited space that don't want two separate battery banks. We stock the dual-purpose ranges from **Fullriver (AGM DC series), Varta Professional, Exide and Kronobat**, covering everything from small motorboats and RIBs to sailing yachts and fishing boats. ## One battery to start the engine and run the boat A pure starter battery delivers a lot of current for a few seconds but copes badly with deep discharges; a deep-cycle battery withstands long discharges but isn't designed for cranking peaks. A **marine dual-purpose battery** sits between the two: thicker plates than a starter battery and a much higher discharge capability, so it can **crank your outboard or inboard engine and also power the boat's loads** without damage. ### When to choose dual purpose - **Boats with a single battery bank** or limited space. - **Motorboats, RIBs and fishing boats** with moderate electronics (sounder, GPS, lights, radio). - **Small and mid-size sailing yachts** that want a simpler installation. - As the only battery where the engine manufacturer allows it; for heavy loads (large fridge, autopilot, inverter) consider a dedicated deep-cycle bank. ### AGM technology: the usual choice on board Most modern dual-purpose batteries are **sealed AGM**: maintenance-free, spill-proof even when the boat heels, highly vibration-resistant and quick to recharge from the engine alternator or a shore charger. Use the [comparison tool](/gb/comparator) to compare capacity (Ah), cranking current and dimensions across series. ## Frequently asked questions about marine dual-purpose batteries ### **What is the difference between dual purpose and deep cycle?** A dual-purpose battery can deliver engine-cranking current and tolerate moderate service discharges; a deep-cycle battery maximises long-discharge cycles but isn't optimised for starting. With a single battery on board, dual purpose is the right compromise. ### **Will a dual-purpose battery start my outboard?** Yes, as long as it meets the minimum cranking current (EN A or MCA) and capacity stated by the engine manufacturer. Also check the battery-box dimensions and terminal type. ### **How long does a marine dual-purpose battery last?** With proper charging and correct winter storage (charged and disconnected, or on a maintainer), a quality AGM dual purpose typically lasts several seasons. Repeated discharge below 50% shortens its life. ### **Can it be mounted at an angle?** Sealed AGM batteries tolerate different mounting positions and will not spill electrolyte as the boat rolls, although upright installation, well secured in its box, is recommended. Catalogue curated by our technical team. **10,549 Trustpilot reviews · 4.4/5**. 24h mainland delivery, free 14-day returns. ## Products in this category | Product | Brand | Price | |---|---|---| | [Marine battery Exide EP800 12V 95Ah AGM](https://baterias.com/gb/battery-exide-ep800-12v-95ah-850a) | EXIDE | 132,65 € | | [Marine battery Varta LA95 12V 85Ah AGM](https://baterias.com/gb/battery-varta-la95agm-12v-95ah-850a) | VARTA | 181,75 € | | [Marine battery Exide EP600 12V 70Ah AGM](https://baterias.com/gb/battery-exide-ep600-12v-70ah-760a) | EXIDE | 104,05 € | | [Marine battery Exide EP1200 12V 140Ah AGM](https://baterias.com/gb/battery-exide-ep1200-12v-140ah-700a) | EXIDE | 269,18 € | | [Marine battery Optima BTDC-5.5 12V 75Ah AGM](https://baterias.com/gb/battery-optima-blue-top-btdc-55-8052-188-12v-75ah) | OPTIMA | 263,05 € | | [Marine battery Exide EP450 12V 50Ah AGM](https://baterias.com/gb/battery-exide-ep450-12v-50ah-750a) | EXIDE | 141,15 € | | [Marine battery Varta LFD140 12V 119Ah](https://baterias.com/gb/battery-varta-lfd140-12v-140ah-800a) | VARTA | 180,72 € | | [Marine battery Varta LA80 12V 77Ah AGM](https://baterias.com/gb/battery-varta-la80agm-12v-80ah-800a) | VARTA | 154,15 € | | [Marine battery Exide ER570 12V 120Ah](https://baterias.com/gb/battery-exide-er570-12v-120ah-760a) | EXIDE | 122,65 € | | [Marine battery Optima BTDC-4.2 12V 55Ah AGM](https://baterias.com/gb/battery-optima-blue-top-btdc-42-8016-253-12v-55ah) | OPTIMA | 216,23 € | | [Marine battery Exide ER350 12V 80Ah](https://baterias.com/gb/battery-exide-er350-12v-80ah-510a) | EXIDE | 84,50 € | | [Marine battery Varta LA105 12V 95Ah AGM](https://baterias.com/gb/battery-varta-la105agm-12v-105ah-950a) | VARTA | 243,20 € | | [Marine battery Exide EP900 12V 100Ah AGM](https://baterias.com/gb/battery-exide-ep900-12v-100ah-720a) | EXIDE | 245,30 € | | [Marine battery Exide ER450 12V 95Ah](https://baterias.com/gb/battery-exide-er450-12v-95ah-650a) | EXIDE | 88,85 € | | [Marine battery Varta LA70 12V 60Ah AGM](https://baterias.com/gb/battery-varta-la70agm-12v-70ah-760a) | VARTA | 140,15 € | ## Technical team (editorial authorship) The FAQs, guides and comparisons on this site are reviewed by the baterias.com technical team — over 25 years of experience validating automotive batteries. → https://baterias.com/gb/technical-team --- *baterias.com — Automotive batteries · 2026-07-15*