Optima BTSLI-4.2 · Marine battery 12V 50Ah 815A AGM
Specifications
| Brand | OPTIMA |
|---|---|
| Part number | BTSLI-4.2 |
| Voltage (V) | 12 |
| Capacity (C20) | 50Ah (c20) |
| Cold cranking amps (EN) | 815A |
| Technology | AGM ESPIRAL |
| Length | 254.00 mm |
| Width | 172.00 mm |
| Height | 173.00 mm |
€181.50
VAT included
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 designbuilt for boat swell and vibration
- Dual functionstarts the engine and powers onboard services
- Sealed and safemaintenance-free even when the boat rolls
Voltage
12 V
Capacity
50 Ah
Cold cranking
815 A
Dimensions
254×175×200 mm
Technology
AGM ESPIRAL
Polarity
Positive on the left
Weight
18,4 kg
Model
OPTIMA BLUE TOP
Compre dos baterías para el molinete de proa de un barco. Perfecto todo. Muy satisfecho. La entrega fue dentro de los plazos establecidos.
Sergi B.Verified purchaseEl servicio, excelente
Alfredo GonzalezGracias por el asesoramiento, al final resultó fácil instalar la batería
Ivan Flores
Reviews originally written in Spanish
Marine battery Optima BTSLI-4.2 Blue Top 50Ah 815A 12V
12VVoltage
50AhCapacity
815ACold cranking
18kgWeight
The Optima BTSLI-4.2 marine battery offers 12 V, 50 Ah and 815 A of cold cranking current (EN) from the Blue Top range with spiral-cell AGM technology, designed for motor and sailing boats, both for engine starting and onboard services. Measuring 254 × 172 × 173 mm and the positive terminal on the left, it is the direct replacement for boats fitted from the factory with a 50 Ah battery of this format.
- Sealed: no spills or gases in the locker.
- Resistant to humidity and salt air.
- Spiral AGM construction, sealed and mountable in any position.
- Ready for starting outboard and inboard engines.
Vehicles compatible with the Optima BTSLI-4.2
The Optima BTSLI-4.2 is compatible with more than 58 vehicles: it is fitted as original equipment or as a replacement by brands such as Fendt, Deutz-Fahr, New Holland, Ford, International-Harvester and Inter Harv.. It is a go-to option when you need a battery for a Fendt, Deutz-Fahr or other models that use this same format. Models from Isuzu and Jeep are added to that list.
Dimensions, polarity and mounting
The Optima BTSLI-4.2 is made in the 254 × 172 × 173 mm format and weighs 18 kg. The positive terminal on the left decides which side the cables end up on: it is the detail that causes most buying mistakes, so check it before ordering. It uses 1 & 21 terminals, the system that anchors and connects it in the vehicle. Checking the three dimensions and the terminal position before buying avoids the most common mistake when replacing a battery.
What Optima does differently
The Optima Red, Yellow and Blue Top are references for high-performance starting, deep cycling and marine use respectively, all with the characteristic six spiral-cell design. All the Optima batteries in our catalogue are genuine product, recently manufactured and covered by the manufacturer's warranty.
The Optima BTSLI-4.2: Blue Top range and spiral-cell AGM technology
Within the Optima catalogue, the Blue Top series groups the references designed for this use. The BTSLI-4.2 is the 50 Ah model of that family, with the same performance as its siblings in other sizes.
In a spiral-cell battery the electrolyte is absorbed and the plates are wound under pressure. That lets it deliver very high current peaks, recharge quickly and be mounted in any position.
How to make it last longer
As a service battery, avoid routine discharges below 50% to extend its cycle life. Charge with a voltage-controlled AGM charger; a fully discharged pure-lead battery may need a specific charger to recover.
Manufacturer's warranty
The Optima BTSLI-4.2 comes with the manufacturer's official warranty against manufacturing defects. Deep discharge from winter lay-up without charging is not covered.
Shipping, delivery and returns
Orders placed before 6:00 pm with the battery in stock ship the same day. Delivery in mainland Spain and Portugal takes 24-48 working hours; for the Balearic Islands and the rest of the European Union allow 3 to 5 working days. You have 14 days to return an unused battery; in mainland Spain and Portugal collection is free. We email you the tracking number as soon as the parcel ships.
BCOM-OPTIMA-BTSLI-4.2
Data sheet
- Brand
- OPTIMA
- Reference
- BTSLI-4.2
- Model
- OPTIMA BLUE TOP
- Voltage (V)
- 12
- Length
- 254.00 mm
- Width
- 172.00 mm
- Height
- 173.00 mm
- Weight
- 18 Kgs
- Technology
- AGM ESPIRAL
- EAN
- 4016987113493
- Terminal layout
- Positive terminal on the left
- Terminal type
- 1 & 21
- Cold cranking amps (EN)
- 815A
- Capacity (C20)
- 50Ah (c20)
- ETN
- 8062520008882
Specific References
- EAN13
- 4016987113493
- MPN
- BTSLI-4.2
4,83/5
1 with verified purchaseLatest reviews
Reviews originally written in Spanish
★★★★★Sergi B.Verified purchase
09/10/2026Experiencia satisfactoria
Compre dos baterías para el molinete de proa de un barco.
Perfecto todo. Muy satisfecho.
La entrega fue dentro de los plazos establecidos.
★★★★★Alfredo Gonzalez
26/07/2026Bien
El servicio, excelente
★★★★★Ivan Flores
16/06/2026Muchas gracias por la ayuda
Gracias por el asesoramiento, al final resultó fácil instalar la batería
★★★★★Jose Angel Bravo
30/04/2026Gran atención al cliente
La atención al cliente es lo mejor de esta web. Muy por encima de la competencia.
★★★★★Sebastian Bravo
06/04/2026Recomendable 100%
Web recomendable 100%. En la competencia ni me cogieron el teléfono
★★★★★Jose Francisco Garcia
02/04/2026Me ayudaron a elegir la batería correcta
Sin vuestra ayuda no hubiera podido instalar la batería. Gracias
★★★★★Alex Gimenez
05/01/2026La entrega en tiempo y forma
Me alegra que cumplen con los tiempos de envío
★★★★★Jose Francisco Iglesias
04/01/2026No sabía que el asesoramiento era gratis, de 10
Usualmente no recibes un trato tan personalizado, pero en esta web me ayudaron con la elección y la instalación de la batería.
★★★★★Andres Gomez
03/01/2026Buen sitio
Creo que esta web es la mejor para adquirir tu batería, muy recomdable
★★★★★Francisco Javier Molina
29/12/2025Rápido y sencillo
Pedí la batería un miércoles a las 4 y me llegó el jueves a las 2
★★★★★Martin Cabrera
22/12/2025Recomendable
Recibí la bateria de mi coche antes de lo previsto
★★★★★Gonzalo Lorenzo
10/12/2025Gracias por la ayuda
Gracias por el asesoramiento, al final resultó fácil instalar la bateria
Codes and references Optima BTSLI-4.2
| Brand | Optima · see all Optima batteries |
|---|---|
| Manufacturer range | OPTIMA BLUE TOP |
| Manufacturer part number (MPN) | BTSLI-4.2 |
| Also known as | BTSLI4.2 · BTSLI 4.2 · 806252000 |
| ETN code | 8062520008882 (short form 806 252 000) |
| EAN-13 barcode | 4016987113493 |
| Dimensions (length × width × height) | 254 × 175 × 200 mm (254x175x200) |
Recommended accessories
Compatible vehicles
The Optima BTSLI-4.2 fits 30 vehicles. Most searched below:
FENDTFarmer1990FENDTFavorit1990DEUTZ-FAHRAgrotron1995ISUZUFORWARD F1990DEUTZ-FAHRAgroplus1996FORD5000-Serie1990NEW HOLLANDSeries T4 POWERSTAR1990NEW HOLLANDWORKMASTER2009INTERNATIONAL-HARVESTERC-Series1990INTERNATIONAL-HARVESTERCM-Series1990INTER HARV.CM-Series1990JEEPPATRIOT (MK74)2007
See all 30 compatible vehicles 
How to change the battery
Guide to replace a marine battery (cranking or house) in 20-30 minutes. Moisture and vibration in marine environments require reinforced hold-downs and sealed copper terminals.
Step 1. Prepare the vehicle
Park on a flat surface, switch off the engine and remove the key. Make sure all lights and electrical accessories are off. Wait 1-2 minutes before starting.
Step 2. Locate the battery compartment
Usually under the passenger bench, engine room or a dedicated ventilated compartment. Verify the compartment is dry and well ventilated before opening.
Step 3. Disconnect the negative (−) terminal
Use the 10 mm wrench to loosen the negative cable nut (black, marked −) and remove the cable from the post. Move it aside so it cannot touch any bodywork.
Step 4. Disconnect the positive (+) terminal
Repeat with the positive cable (red, marked +). Important: never let a terminal touch metal of the car while the other is still connected.
Step 5. Remove the old battery
Marine batteries are heavy (15-50 kg). If it has rope handles, use them; otherwise have a carry strap ready. Secure the new one with metal hold-downs (not plastic) to resist sea-state vibration.
Step 6. Install the new battery
Place the battery in the same orientation as the old one (positive terminal on the same side). Tighten the hold-down clamp firmly.
Step 7. Connect the cables
Connect the positive (+) terminal first, then the negative (−). Tighten the nuts with the wrench until each terminal does not move. Apply anti-spark grease if you have any.
Step 8. Verify circuit + water protection
Apply dielectric grease on terminals to prevent salt-air corrosion. Check the engine charging circuit delivers 13.8-14.4 V at 2,000 rpm.
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 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 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.
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 10:00–13:30 and 16:40–18:00 (Spanish time, CET)). The BTSLI-4.2 fits 30 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.
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