Optima BTDC-4.2 Blue Top · Marine battery 55Ah 765A AGM

Marine battery Optima BTDC-4.2 Blue Top 55Ah 765A 12V

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.