# Optima BTSLI-4.2 · Boat battery 12V 50Ah 815A

![Optima BTSLI-4.2 · Boat battery 12V 50Ah 815A](https://bateriasonline.es/3848-home_default/optima-btsli-4-2.jpg)

> Optima BTSLI-4.2 (ETN 806252000): 50 Ah boat battery, 815 A (EN), 254×175×200 mm, positive terminal on the left, spiral AGM.

**Category:** [Marine and boat batteries](https://bateriasonline.es/en/marine-boat-batteries) → [Optima](https://bateriasonline.es/en/optima-batteries)

- **Canonical URL**: https://bateriasonline.es/en/optima-btsli-4-2
- **Language**: en
- **Brand**: Optima
- **Reference**: BOL-OPTIMA-BTSLI-4.2
- **EAN**: 4016987113493
- **MPN**: BTSLI-4.2
- **Price**: 177,59 € (VAT incl., Spain)
- **Last updated**: 2026-10-27

## Technical specifications

| Feature | Value |
|---|---|
| Brand | Optima |
| Range | OPTIMA BLUE TOP |
| Application | Boats |
| Technology | Spiral AGM |
| Voltage | 12 V |
| Capacity | 50 Ah |
| Cold cranking amps (EN) | 815 A |
| Length | 254 mm |
| Width | 175 mm |
| Height | 200 mm |
| Weight | 18.4 kg |
| Polarity | Positive terminal on the left |
| Terminal type | 1 & 21 |
| ETN code | 806252000 |

## Quick description

The Optima BTSLI-4.2 (ETN 806 252 000, also written 806252000) is a boat battery with 12 V, 50 Ah and 815 A cold cranking current, measuring 254 × 175 × 200 mm, with the positive terminal on the left.

## Description

## Where the Optima BTSLI-4.2 fits

The Optima BTSLI-4.2 is made for marine use. Fit the BTSLI-4.2 securely on board and away from bilge water.
The BTSLI-4.2 belongs to the Optima OPTIMA BLUE TOP range. [See all Optima batteries](https://bateriasonline.es/en/optima-batteries)

## Spiral AGM technology in the BTSLI-4.2

Inside, the BTSLI-4.2 rolls its plates into cylindrical cells (spiral AGM). It is the basis of OPTIMA batteries.

## Optima BTSLI-4.2 vs BTDC-4.2 and BTDC-5.0: which one to choose?

Torn between the BTSLI-4.2 and another similar Optima? This is what changes:

| Model | Capacity | Cold cranking (EN) | Dimensions (mm) | Positive | Weight |
|---|---|---|---|---|---|
| Optima BTSLI-4.2 (this one) | 50 Ah | 815 A | 254 × 175 × 200 | left | 18.4 kg |
| Optima BTDC-4.2 | 55 Ah | 765 A | 254 × 175 × 200 | left | 20.6 kg |
| Optima BTDC-5.0 | 66 Ah | 765 A | 309 × 172 × 221 | left | 24.4 kg |

- Optima BTDC-4.2: 5 Ah more, 50 A less cranking power, the same dimensions.
- Optima BTDC-5.0: 16 Ah more, 50 A less cranking power, a different case (309 × 172 × 221 mm).

## Equivalents and alternatives to the Optima BTSLI-4.2

No other reference in the catalogue fully matches the dimensions and polarity of the BTSLI-4.2; you will find the closest ones among our [marine and boat batteries](https://bateriasonline.es/en/marine-boat-batteries).

## Optima BTSLI-4.2 codes and part numbers

This is how the Optima BTSLI-4.2 appears on the label and in parts catalogues:

| Commercial reference | BTSLI-4.2 |
|---|---|
| ETN code | 806252000 (also 806 252 000) |
| EAN | 4016987113493 |
| Case size according to Optima | 34 (BCI) |
| Base hold-down | B00 |
| Terminal type | 1 & 21 |
| Also known as | Optima 806252000 · Optima 806 252 000 |

## Check this before ordering the Optima BTSLI-4.2

- The BTSLI-4.2 delivers 815 A cold cranking (EN standard); do not go below what your original battery states.
- With 50 Ah, the BTSLI-4.2 replaces an original battery of that capacity or slightly less.
- The BTSLI-4.2 has the positive terminal on the left: compare it with your current battery.
- The BTSLI-4.2 needs 254 × 175 × 200 mm of space: measure it with the hold-down clamp in place.

## Frequently asked questions about the Optima BTSLI-4.2

### Optima BTSLI-4.2 or BTDC-4.2?

Compared with the BTSLI-4.2, the Optima BTDC-4.2 has 5 Ah more and 50 A less cranking power. The BTSLI-4.2 cranks harder; the BTDC-4.2 is only a good option if your original battery says 765 A or less. Both measure 254 × 175 × 200 mm, so they fit the same tray.

### What is the ETN code of the Optima BTSLI-4.2?

806252000, also written 806 252 000. The ETN (European Type Number) is printed on the label and used in parts catalogues.

### How much does the Optima BTSLI-4.2 weigh?

The BTSLI-4.2 weighs 18.4 kg. For reference, the Optima BTDC-4.2 (55 Ah) weighs 20.6 kg.

### Which side is the positive terminal on the Optima BTSLI-4.2?

The BTSLI-4.2 has the positive terminal on the left, looking at the battery from its long side with the terminals closest to you.

## More batteries to compare with the BTSLI-4.2

- [Other marine and boat batteries](https://bateriasonline.es/en/marine-boat-batteries)
- [The whole Optima range](https://bateriasonline.es/en/optima-batteries)

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