# Marine battery Optima BTDC-5.0 12V 66Ah 765A AGM

![Marine battery Optima BTDC-5.0 12V 66Ah 765A AGM](https://baterias.com/844-home_default/battery-optima-blue-top-btdc-50-8027-227-12v-66ah.jpg)

> Optima BTDC-5.0 marine battery 12V 66Ah 765A AGM. BLUE TOP range. Dimensions 309×172×221 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-btdc-50-8027-227-12v-66ah
- **Language**: en-GB
- **Brand**: OPTIMA
- **Reference**: BCOM-OPTIMA-BTDC-5.0
- **EAN**: 4016987130346
- **MPN**: BTDC-5.0
- **Price**: 225,70 €
- **Stock**: In stock

## Technical specifications

| Feature | Value |
|---|---|
| Brand | OPTIMA |
| Reference | BTDC-5 |
| Model | OPTIMA BLUE TOP |
| Voltage (V) | 12 V |
| Largo | 309 mm |
| Ancho | 172 mm |
| Alto | 200 mm |
| Peso | 22.7 kg |
| Tecnología | AGM ESPIRAL |
| EAN | 4016987130346 |
| Terminal layout | Positive terminal on the left |
| Terminal type | 1 & 21 |
| Cold cranking amps (EN) | 845 A |
| Capacity (C20) | 66 Ah (c20) |
| Capacity (C5) | 61 Ah (c5) |
| ETN | 8272270008882 |

## Quick description

**Optima BTDC-5.0 12V 66Ah 765A** 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
66 Ah C20

🔋 Cold cranking
765 A EN-1

📏 Dimensions
309×172×221 mm

⚙️ Technology
AGM ESPIRAL

🧭 Polarity
Positive on the left

⚖️ Weight
24,4 kg

🏷️ Model
OPTIMA BLUE TOP

## Description

## Marine battery Optima BTDC-5.0 Blue Top 66Ah 845A 12V

12*V* Voltage
66*Ah* Capacity
845*A* Cold cranking
22.70*kg* Weight

With **66 Ah** at **12 V** and **845 A** of cold cranking current (EN), the **Optima BTDC-5.0** from the **Blue Top** range is built for motor and sailing boats, both for engine starting and onboard services. Measuring 309 × 172 × 200 mm and the positive terminal on the left, it is the direct replacement for boats fitted from the factory with a 66 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.

### What the Optima BTDC-5.0 is for

With 66 Ah, the Optima BTDC-5.0 covers motor and sailing boats, both for engine starting and onboard services. At the end of the season, charge it fully before winter storage. Check that it matches your current battery in dimensions, terminals and hold-down: this reference has a weight of 22.70 kg and 1 & 21 terminals.

### The Optima BTDC-5.0: Blue Top range and spiral-cell AGM technology

Within the Optima catalogue, the **Blue Top** series groups the references designed for this use. The BTDC-5.0 is the 66 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.

### Size, terminals and hold-down of the Optima BTDC-5.0

In terms of format, the Optima BTDC-5.0 measures 309 × 172 × 200 mm (length × width × height) and weighs 22.70 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.

### Optima: the maker behind the BTDC-5.0

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.

### Usage and maintenance tips

At the end of the season, charge the battery fully and, if possible, keep it on a charger over the winter lay-up. Protect the terminals with dielectric grease and check the fixing: vibration and swell loosen connections.

### Warranty and coverage

The Optima BTDC-5.0 comes with the **manufacturer's official warranty** against manufacturing defects. Deep discharge from winter lay-up without charging is not covered.

### When you get it and how to return it

Orders placed **before [[ks:cutoff]]** with the battery in stock ship the same day. Delivery in mainland Spain and Portugal takes 24-48 working hours; for the Balearic and Canary Islands and the rest of the European Union allow 3 to 5 working days. You have **[[ks:return_days]] 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.

## Frequently asked questions

### Is the Optima BTDC-5.0 an AGM battery and what are the benefits of AGM?

Yes. The BTDC-5.0 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 fit the BTDC-5.0 model in my boat?

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 long does the Optima BTDC-5.0 battery last?

Expected lifespan of the Optima BTDC-5.0 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 BTDC-5.0 battery?

Dimensions (length × width × height) are 309×172×221 mm — also written as 309x172x221 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-5.0 battery have?

The manufacturer reference (MPN) is BTDC-5.0 and its ETN code is 8272270008882 (short form 827 227 000), the European identifier used in spare-part catalogues. The EAN-13 barcode is 4016987130346. 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-5.0 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-5.0 typically fits a wide range of European vehicles thanks to its standard DIN case format.

### What are the equivalents of the BTDC-5.0 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.


## Reviews

- **Average rating**: 4.8 / 5 (35 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 · 2026-09-30*