Optima BTDC-4.2 · Marine battery 12V 55Ah 765A AGM
Specifications
| Brand | OPTIMA |
|---|---|
| Part number | BTDC-4.2 |
| Voltage (V) | 12 |
| Capacity (C20) | 55Ah (c20) |
| Capacity (C5) | 52Ah (c5) |
| Cold cranking amps (EN) | 765A |
| Technology | AGM ESPIRAL |
| Length | 254.00 mm |
| Width | 172.00 mm |
€216.90
VAT included
Optima BTDC-4.2 12V 55Ah 765A is a marine battery, vibration- and deep-discharge resistant, suitable both for outboard engine starting and for onboard auxiliary services (navigation lights, GPS, sonar, fridge). Sealed and maintenance-free.
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
55 Ah
Cold cranking
765 A
Dimensions
254×175×200 mm
Technology
AGM ESPIRAL
Polarity
Positive on the left
Weight
20,6 kg
Model
OPTIMA BLUE TOP
Marine battery Optima BTDC-4.2 Blue Top 55Ah 765A 12V
12VVoltage
55AhCapacity
765ACold cranking
20.30kgWeight
The Optima BTDC-4.2 with spiral-cell AGM technology is a marine battery with 55 Ah and 765 A of cold cranking current (EN) for motor and sailing boats, both for engine starting and onboard services. It measures 254 × 172 × 173 mm and the positive terminal on the left, the format sought by anyone replacing a 55 Ah battery in boats.
- Tolerates the daily cycling of a boat in season.
- Powers onboard services: lights, sounder, GPS, fridge.
- Reinforced case against vibration and swell.
- Spiral cells: maximum vibration resistance and very powerful cranking.
What the Optima BTDC-4.2 is for
The Optima BTDC-4.2 is designed for motor and sailing boats, both for engine starting and onboard services. If it is your starter battery, run the services from a separate battery; if it is a service battery, avoid routinely discharging it beyond 50%. Check that it matches your current battery in dimensions, terminals and hold-down: this reference has a weight of 20.30 kg and 1 & 21 terminals.
Dimensions, polarity and mounting
In terms of format, the Optima BTDC-4.2 measures 254 × 172 × 173 mm (length × width × height) and weighs 20.30 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.
Why choose Optima batteries
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. We guarantee that every Optima arrives new, charged and with the manufacturer's full warranty.
The Optima BTDC-4.2: Blue Top range and spiral-cell AGM technology
The BTDC-4.2 is part of the Optima Blue Top range. Choosing the right reference within the series comes down to capacity, dimensions and terminals: technology and quality are common to the whole family.
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. Protect the terminals with dielectric grease and check the fixing: vibration and swell loosen connections.
Manufacturer's warranty
The Optima BTDC-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
Order before 6:00 pm with stock available and it leaves today: mainland Spain and Portugal receive it in 24-48 working hours, the islands and the rest of the EU in 3 to 5 days. You have 14 days to return it if it has not been installed, with free collection on the mainland, and shipment tracking by email.
BCOM-OPTIMA-BTDC-4.2
Data sheet
- Brand
- OPTIMA
- Reference
- BTDC-4.2
- Model
- OPTIMA BLUE TOP
- Voltage (V)
- 12
- Length
- 254.00 mm
- Width
- 172.00 mm
- Height
- 173.00 mm
- Weight
- 20.3 Kgs
- Technology
- AGM ESPIRAL
- EAN
- 4016987113547
- Terminal layout
- Positive terminal on the left
- Terminal type
- 1 & 21
- Cold cranking amps (EN)
- 765A
- Capacity (C20)
- 55Ah (c20)
- Capacity (C5)
- 52Ah (c5)
- ETN
- 8162530008882
Specific References
- EAN13
- 4016987113547
- MPN
- BTDC-4.2
Codes and references Optima BTDC-4.2
| Brand | Optima · see all Optima batteries |
|---|---|
| Manufacturer range | OPTIMA BLUE TOP |
| Manufacturer part number (MPN) | BTDC-4.2 |
| Also known as | BTDC4.2 · BTDC 4.2 · 806252000 |
| ETN code | 8062520008882 (short form 806 252 000) |
| EAN-13 barcode | 4016987113547 |
| Dimensions (length × width × height) | 254 × 175 × 200 mm (254x175x200) |
Comparison: Optima BTDC-4.2 vs equivalents
The Optima BTDC-4.2 is interchangeable with these equivalent references: BTSLI-4.2 (Optima).
| Product | Specifications | Technology | Price |
|---|---|---|---|
Optima
BTDC-4.2
This battery
|
12V 50Ah 815A | AGM | €216.90 |
Optima
BTSLI-4.2
|
12V 50Ah 815A | AGM | €181.50 |
Equivalences verified by our technical team: same dimensions, polarity, capacity and CCA. Official manufacturer warranty on every option.
Recommended accessories
Compatible vehicles
The Optima BTDC-4.2 fits 30 vehicles. Most searched below:
FENDTFarmer1990FENDTFavorit1990DEUTZ-FAHRAgrotron1995ISUZUFORWARD F1990DEUTZ-FAHRAgroplus1996FORD5000-Serie1990NEW HOLLANDWORKMASTER2009NEW HOLLANDSeries T4 POWERSTAR1990INTERNATIONAL-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 BTDC-4.2 an AGM battery and what are the benefits of AGM?
Yes. The BTDC-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 BTDC-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 measurements of the BTDC-4.2 model?
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 BTDC-4.2 battery have?
The manufacturer reference (MPN) is BTDC-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 4016987113547. It belongs to the OPTIMA BLUE TOP range. Any of these codes identifies exactly this battery when requesting quotes or comparing prices.
Is the BTDC-4.2 valid for my vehicle?
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 BTDC-4.2 fits 30 verified vehicle versions in our database.
What are the equivalents of the BTDC-4.2 model?
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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