# Marine battery Optima BTSLI-4.2 12V 50Ah 815A AGM ![Marine battery Optima BTSLI-4.2 12V 50Ah 815A AGM](https://baterias.com/3808-home_default/battery-optima-blue-top-btsli-42-8006-252-12v-50ah.jpg) > Optima BTSLI-4.2 marine battery 12V 50Ah 815A AGM. BLUE TOP range. Dimensions 254×175×200 mm, + terminal on the left. Cranking and house duties. **Category:** [Boat Batteries](https://baterias.com/gb/boat-batteries) → [OPTIMA](https://baterias.com/gb/optima) - **Canonical URL**: https://baterias.com/gb/battery-optima-blue-top-btsli-42-8006-252-12v-50ah - **Language**: en-GB - **Brand**: OPTIMA - **Reference**: BCOM-OPTIMA-BTSLI-4.2 - **EAN**: 4016987113493 - **MPN**: BTSLI-4.2 - **Price**: 180,80 € - **Stock**: In stock ## Technical specifications | Feature | Value | |---|---| | Brand | OPTIMA | | Reference | BTSLI-4.2 | | Model | OPTIMA BLUE TOP | | Voltaje | 12 V | | Largo | 254 mm | | Ancho | 172 mm | | Alto | 173 mm | | Peso | 18 kg | | Tecnología | AGM ESPIRAL | | EAN | 4016987113493 | | Scheme | Positive terminal on the left | | Terminal | 1 & 21 | | Arranque en frío CCA EN | 815 A | | Capacidad C20 (Ah) | 50 Ah (c20) | | ETN | 8062520008882 | ## Quick description **Optima BTSLI-4.2 12V 50Ah 815A** is a marine battery with reinforced anti-vibration case for moorings and offshore use. Tolerates the typical daily cycles on a boat (engine start + night-time services such as lights, sonar, fridge) and holds voltage even when the hull is rolling in open sea. ### Why this marine battery? - **Marine design** built for boat swell and vibration - **Dual function** starts the engine and powers onboard services - **Sealed and safe** maintenance-free even when the boat rolls 🔌 Voltage 12 V ⚡ Capacity 50 Ah C20 🔋 Cold cranking 815 A EN-1 📏 Dimensions 254×175×200 mm ⚙️ Technology AGM ESPIRAL 🧭 Polarity Positivo a la izquierda ⚖️ Weight 18,4 kg 🏷️ Model OPTIMA BLUE TOP ## Description ## Battery Optima BTSLI 4.2 50Ah 815A 12V The Battery OPTIMA BTSLI-4.2 50Ah 815A 12V BLUE TOP belongs to the Optima Bluetop battery range This high -end battery incorporates Spiracell technology (cells with spiral structure inside that enhances the performance of the batteries) created by Optima, which offers more prolonged service time, faster recharges and even twiceconventional nautical batteries. Specially designed to overcome the great demands of nautical applications offering a reliable energy supply, totally free of leaks and does not require maintenance.Totally free of leaks and does not require maintenance. Among our Bluetop products catalog you will find double -use batteries that S can use in any deep cycle application (navigation accessory, on -board applications, outboard engine, bow propuls) or starting. ### Ideal for: - Start applications - Agricultural machines - Construction vehicles - Emergency vehicles - Generators - Trams ### Battery advantages and characteristics OPTIMA BTSLI-4.2 50Ah 815A 12V - Long useful life.Lasts up to three times more than conventional flat plates batteries - Constant performance - Greater power.More power during the first one, two, five and ten seconds of the starting process compared to similar lead-acid batteries. - Perfect for seasonal uses.If it is fully charged, it may not be used for a period of up to 12 months at room temperature (or lower) and yet start a car. - x15 times more resistant to vibrations than standard lead-acid batteries - Free of mantenimient - It can be installed almost in any position ### How to find the right battery for your vehicle or device? Optimal AGM AGM batteries are not comparable to any other battery in the world.Its Spi-Dpiell technology is among the most advanced lead-acid battery technologies available in the market. If you are not sure what cover color is better under your hood, do not hesitate to contact us and we will be happy to advise you. ### Why choose an optimal battery? If you look for the maximum possible power or a battery to work in the toughest working conditions.Do not hesitate, choose an optima battery ### OPTIMA - LEADING BRAND IN THE SECTOR With a 40 -year history of technological innovation and engineering, Optima® products offer unstoppable power for extreme enthusiasts and other people who require the final source of energy. In the 1970s, Optima Batteries presented the first main maintenanceless lead batteries for commercial and military use and the first high-performance AGM automotive batteries, but optimal innovation did not stop there.Optima the industry revolutionized with the introduction of its exclusive Spiord Technology® that grants certain key benefits such as: - Incredibly high starter characteristics in a small battery - Up to 15 times more resistance to vibrations than a conventional battery - Have a higher life cycle compared to traditional batteries If you want additional information about Battery Optima BTSLI 4.2, you can download the product's technical sheet at the following link: [ Download technical sheet Optima BTSLI 4.2 50Ah 815A 12V](/fichastecnicas/data-sheet-battery-optima-btsli-4_2-50ah-815a-12v-en.pdf) ## Frequently asked questions ### Is the Optima BTSLI-4.2 an AGM battery and what are the benefits of AGM? Yes. The BTSLI-4.2 from Optima uses AGM (Absorbent Glass Mat) technology: a sealed lead-acid battery where the electrolyte is absorbed in a glass-fibre mat. It withstands more charge/discharge cycles than a conventional one, handles heat better and is the required technology for boats with advanced Start-Stop and regenerative braking. Expected lifespan: 5-8 years under normal conditions. ### How do I know if the BTSLI-4.2 model fits my boat? Three ways: 1) enter your number plate in the finder (DGT/DVLA/KBA auto-detect your model and engine); 2) check the "Compatible vehicles" tab on this page, where we list every vehicle verified by our technical team for the BTSLI-4.2; 3) if you cannot find your model, message us on WhatsApp with brand, model, engine and year — we reply during business hours (Mon–Fri 9:00–18:00 CET). ### How do I change this battery step by step? In most boats it fits in 15-30 minutes with a 10 mm wrench; if the battery is under the seat or in the boot the time can double. See the step-by-step guide on this page. Quick summary: 1) switch off the engine and remove the key; 2) locate the original battery (engine bay, boot or under seat); 3) disconnect the negative (−) terminal first, then the positive (+); 4) loosen the hold-down clamp and remove the old battery; 5) fit the new one in the same orientation — match the polarity shown on the product sheet; 6) connect the positive (+) first, then the negative (−). On boats with Start-Stop or BMS, register the battery via OBD so the alternator applies the correct charging profile. ### How many years of warranty does the BTSLI-4.2 model cover? This battery includes 1 year of official manufacturer warranty against manufacturing defects. Coverage includes cell breakdowns, internal short-circuits and abnormal capacity decreases. Wear from misuse (prolonged overcharging, wrong charger or faulty alternator) is not covered. On confirmed defect after technical inspection, we replace the BTSLI-4.2 model at no cost. ### How long does Optima BTSLI-4.2 delivery take? In mainland Spain and Portugal it arrives in 24 h if you order before 17:00 and the battery is in stock — it leaves the same day and arrives the next business day. Afternoon or weekend orders ship the next business day. For Balearics, Canaries and other EU destinations, allow 2-5 days. Shipping cost is calculated in the cart based on destination and service (standard, express, cash on delivery). Tracking number is sent by email + SMS as soon as the parcel ships. ### Can I return the Optima BTSLI-4.2 battery if it doesn't fit or doesn't work? Yes. You have 14 days from delivery to return it. In mainland Spain and Portugal returns are FREE — we cover the return shipping cost via prepaid label. In other EU countries the return shipping cost is the customer's. It must arrive in its original packaging with no signs of installation. If it was defective, the warranty covers replacement even after the 14-day period. ### How much does the Optima BTSLI-4.2 battery cost? The current price at baterias.com is 180,80 € (VAT included; 149,42 € excl. VAT), updated every 24 hours. The applicable VAT may vary with the destination country and is confirmed in the cart. Shipping cost is calculated in the cart based on destination and chosen service (standard, express, cash on delivery). ### Where can I buy the Optima BTSLI-4.2 battery? At baterias.com — authorised distributor with real stock, 24h delivery in mainland Spain and Portugal if you order before 17:00, and full manufacturer warranty. Shipping cost is calculated in the cart based on destination and chosen service (standard, express, cash on delivery). Secure payment by card, Bizum, PayPal or bank transfer. If you choose at-home installation, our technician will take the used battery and dispose of it through an authorised collection point. ### How many years does this battery last? Expected lifespan of the Optima BTSLI-4.2 is 5 to 8 years in mild-climate boat use with Start-Stop. In cold regions it drops slightly due to cold-start stress; in very hot regions it also drops because of electrolyte evaporation. To extend its life: avoid deep discharges (headlights on with engine off), have the alternator checked yearly, and keep the battery clean and properly secured. ### What are the dimensions of the Optima BTSLI-4.2 battery? Dimensions (length × width × height) are 254×175×200 mm — also written as 254x175x200 mm — following the European DIN standard. Always measure the space in your boat before buying: even one extra millimetre can prevent the hold-down clamp from closing. The height shown includes the terminals. ### How much does the Optima BTSLI-4.2 battery weigh? It weighs 18,4 kg. Most of the weight is lead. If you plan to fit it yourself, use gloves and a carrying strap (AGM batteries are slightly heavier than conventional due to the absorbent glass-mat fibre). ### How many amps does the Optima BTSLI-4.2 battery have? Nominal capacity 50 Ah[?cca: and [cold-cranking amps 815 A]] at 12 V. Ah measure the total energy available (autonomy); CCA (also written A in cold or EN under the European standard) measure the instantaneous power to crank the starter motor. A battery with more CCA starts better in winter; one with more Ah keeps accessories on for longer. ### What ETN and EAN codes does the Optima BTSLI-4.2 battery have? The manufacturer reference (MPN) is BTSLI-4.2 and its ETN code is 8062520008882 (short form 806 252 000), the European identifier used in spare-part catalogues. The EAN-13 barcode is 4016987113493. It belongs to the OPTIMA BLUE TOP range. Any of these codes identifies exactly this battery when requesting quotes or comparing prices. ### Will the Optima BTSLI-4.2 battery fit my boat? Three options to confirm: 1) enter your number plate in the finder (DGT/DVLA/KBA auto-detect your model and engine); 2) check the "Compatible vehicles" tab on this page, where we list every vehicle verified by our technical team; 3) if you cannot find your model, message us on WhatsApp with brand, model, engine and year — we reply during business hours (Mon–Fri 9:00–18:00 CET). The BTSLI-4.2 fits 58 verified vehicle versions in our database. ### Which batteries are equivalent to the Optima BTSLI-4.2? Directly interchangeable batteries (same dimensions, same polarity, same Ah and CCA) are the OEM equivalents from leading brands: Bosch, Tudor, Exide and, depending on the model, Banner or Yuasa. Exact equivalence depends on technology — an EFB cannot be replaced with a conventional battery in Start-Stop boats. See the "Equivalents" section to view recommended options at the same performance level. ### Is this battery a better choice than another equivalent? This battery and its equivalents from Bosch, Tudor or Exide are technically comparable: same dimensions, same voltage and same capacity. The differences are warranty (Varta and Bosch: 2 years; Tudor and Exide: 2 years on the equivalent line), manufacturing plant (Varta and Bosch share origin in the Clarios Group; Tudor and Exide belong to Exide Technologies) and price. For private use any of these brands will give 4-6 years of life. Compare them in the "Equivalents" section. ### What reviews does the BTSLI-4.2 model have? The average rating of the Optima BTSLI-4.2 on baterias.com is 4.77/5 from 32 verified customer reviews. The product rating, when available, is shown on the product page next to the stars. You can also check our public Trustpilot profile at shop level (4.5/5 from 11,281+ verified reviews). Most-praised points: reliable cold start, lifespan above 5 years and fast delivery; most common complaints mention BMS-equipped boats that need OBD registration after fitting. ## Compatible vehicles This battery fits 58 vehicles. Most searched: - [FENDT Farmer (1990)](https://baterias.com/gb/batteries-for-agricultural-and-construction-vehicles/fendt/farmer) - [FENDT Farmer (1990)](https://baterias.com/gb/batteries-for-construction-and-agricultural-machinery/fendt/farmer) - [DEUTZ-FAHR Agrotron (1995)](https://baterias.com/gb/batteries-for-agricultural-and-construction-vehicles/deutz-fahr/agrotron) - [FENDT Favorit (1990)](https://baterias.com/gb/batteries-for-construction-and-agricultural-machinery/fendt/favorit) - [DEUTZ-FAHR Agrotron (1995)](https://baterias.com/gb/batteries-for-construction-and-agricultural-machinery/deutz-fahr/agrotron) - [ISUZU FORWARD F (1990)](https://baterias.com/gb/batteries-for-truck/isuzu/forward-f) - [FORD 5000-Serie (1990)](https://baterias.com/gb/batteries-for-agricultural-and-construction-vehicles/ford/5000-serie) - [DEUTZ-FAHR Agroplus (1996)](https://baterias.com/gb/batteries-for-construction-and-agricultural-machinery/deutz-fahr/agroplus) - [FORD 5000-Serie (1990)](https://baterias.com/gb/batteries-for-construction-and-agricultural-machinery/ford/5000-serie) - [NEW HOLLAND Series T4 POWERSTAR (1990)](https://baterias.com/gb/batteries-for-agricultural-and-construction-vehicles/new-holland/series-t4-powerstar) - [NEW HOLLAND WORKMASTER (2009)](https://baterias.com/gb/batteries-for-agricultural-and-construction-vehicles/new-holland/workmaster) - [NEW HOLLAND Series T4 POWERSTAR (1990)](https://baterias.com/gb/batteries-for-construction-and-agricultural-machinery/new-holland/series-t4-powerstar) - [INTERNATIONAL-HARVESTER CM-Series (1990)](https://baterias.com/gb/batteries-for-agricultural-and-construction-vehicles/international-harvester/cm-series) - [INTERNATIONAL-HARVESTER C-Series (1990)](https://baterias.com/gb/batteries-for-construction-and-agricultural-machinery/international-harvester/c-series) - [INTER HARV. C-Series (1990)](https://baterias.com/gb/batteries-for-agricultural-and-construction-vehicles/inter-harv/c-series) ## Reviews - **Average rating**: 4.77 / 5 (32 reviews) ## 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 · 2026-08-23*