# Fulmen FK800 · Start-Stop battery 12V 80Ah 800A

![Fulmen FK800 · Start-Stop battery 12V 80Ah 800A](https://bateriasonline.es/2658-home_default/fulmen-fk800.jpg)

> Fulmen FK800: 80 Ah Start-Stop battery, 800 A (EN), 315×175×190 mm, positive terminal on the right, L4 case, AGM. Equivalent to Exide EK820 and Tudor TK820.

**Category:** [Start-Stop batteries (AGM and EFB)](https://bateriasonline.es/en/start-stop-batteries-agm-efb) → [Fulmen](https://bateriasonline.es/en/fulmen-batteries)

- **Canonical URL**: https://bateriasonline.es/en/fulmen-fk800
- **Language**: en
- **Brand**: Fulmen
- **Reference**: BOL-FULMEN-FK800
- **EAN**: 3661024045728
- **MPN**: FK800
- **Last updated**: 2026-11-07

## Technical specifications

| Feature | Value |
|---|---|
| Brand | Fulmen |
| Range | FULMEN AGM |
| Application | Start-Stop cars |
| Technology | AGM |
| Voltage | 12 V |
| Capacity | 80 Ah |
| Cold cranking amps (EN) | 800 A |
| Length | 315 mm |
| Width | 175 mm |
| Height | 190 mm |
| Weight | 23.1 kg |
| Polarity | Positive terminal on the right |
| Case size | L4 (315 × 175 × 190 mm) |

## Quick description

Fulmen FK800: Start-Stop battery (AGM) with 12 V, 80 Ah and 800 A cold cranking current, case size L4 (315 × 175 × 190 mm), with the positive terminal on the right.

## Description

## Who the Fulmen FK800 is for

The Fulmen FK800 is a battery for cars with Start-Stop: it withstands many more starting and partial-discharge cycles than a conventional battery and powers the electronics every time the engine stops at the lights. The FK800 is designed for cars that switch the engine off at every stop and restart it dozens of times per trip.
At 80 Ah it sits in the range of compact and mid-size diesels, SUVs and MPVs. The FK800 belongs to the Fulmen FULMEN AGM range. [More Fulmen batteries](https://bateriasonline.es/en/fulmen-batteries)

## Fulmen FK800 vs FK820 and FK720

What sets the FK800 apart from its neighbours in the Fulmen range:

| Model | Capacity | Cold cranking (EN) | Dimensions (mm) | Positive | Weight |
|---|---|---|---|---|---|
| Fulmen FK800 (this one) | 80 Ah | 800 A | 315 × 175 × 190 | right | 23.1 kg |
| Fulmen FK820 | 82 Ah | 800 A | 315 × 175 × 190 | right | 23.3 kg |
| Fulmen FK720 | 72 Ah | 760 A | 278 × 175 × 190 | right | 20.6 kg |

- Fulmen FK820: 2 Ah more, the same cranking power, the same L4 case.
- Fulmen FK720: 8 Ah less, 40 A less cranking power, a different case (278 × 175 × 190 mm).

## Fulmen FK800 codes and part numbers

Look for any of these FK800 codes on your current battery or in the manufacturer's catalogue:

| Commercial reference | FK800 |
|---|---|
| EAN | 3661024045728 |
| Case size (EN) | L4 |
| Not to be confused with | Fulmen FK600 (60 Ah, 680 A), Fulmen FK700 (70 Ah, 760 A), Fulmen FK820 (82 Ah, 800 A) |

## Equivalents and alternatives to the Fulmen FK800

As the FK800 is an AGM battery, we only list other AGM batteries with its dimensions and polarity: neither an EFB nor a conventional battery can replace it.

| Model | Technology | Capacity | Cold cranking (EN) | Dimensions (mm) |
|---|---|---|---|---|
| Varta A6 | AGM | 80 Ah | 800 A | 315 × 175 × 190 |
| Deta DK800 | AGM | 80 Ah | 800 A | 315 × 175 × 190 |
| Exide EK820 | AGM | 82 Ah | 800 A | 315 × 175 × 190 |
| Tudor TK820 | AGM | 82 Ah | 800 A | 315 × 175 × 190 |
| Deta DK820 | AGM | 82 Ah | 800 A | 315 × 175 × 190 |
| Fulmen FK820 | AGM | 82 Ah | 800 A | 315 × 175 × 190 |

Its Bosch equivalent is the Bosch S5 A11, the same as for the Varta A6. Bosch is not part of our catalogue; we list it so you can compare.

## Before ordering the FK800, check this

- Length, width and height of the FK800: 315 × 175 × 190 mm (European case size L4).
- The FK800 has the positive terminal on the right: compare it with your current battery.
- Capacity of the FK800: 80 Ah; the same as your current battery or slightly more is fine.
- The FK800 delivers 800 A cold cranking (EN standard); do not go below what your original battery states.
- The FK800 is AGM: it replaces an AGM or an EFB of the same size. You can swap an EFB for an AGM, but not an AGM for an EFB.

## Inside the FK800: AGM technology

The FK800 is AGM: the electrolyte is absorbed in glass fibre mats, so it is sealed and spill-proof. Being sealed, the FK800 can be fitted in the boot or under a seat with no risk of spills.

## Frequently asked questions about the Fulmen FK800

### Fulmen FK800 or FK820?

Compared with the FK800, the Fulmen FK820 has 2 Ah more. With the same cranking power (800 A), the FK800 and the FK820 differ in capacity: the one with more Ah supports more load with the engine off. Both measure 315 × 175 × 190 mm, so they fit the same tray.

### Can the Fulmen FK800 be used in a car with Start-Stop?

Yes. As an AGM battery, the FK800 handles automatic engine stop and brake energy recovery, and it can replace an EFB of the same size.

### How much does the Fulmen FK800 weigh?

The FK800 weighs 23.1 kg. For reference, the Fulmen FK820 (82 Ah) weighs 23.3 kg.

### Which battery is equivalent to the Fulmen FK800?

Only other AGM batteries with its dimensions and polarity: Varta A6, Deta DK800 and Exide EK820. Neither an EFB nor a conventional battery replaces the FK800. Its Bosch equivalent is the Bosch S5 A11, the same as for the Varta A6. Bosch is not part of our catalogue; we list it so you can compare.

### What case size is the Fulmen FK800?

Case size L4: 315 × 175 × 190 mm. The FK800 fits any standard L4 battery tray such as the Varta A6.

### Which side is the positive terminal on the Fulmen FK800?

The FK800 has the positive terminal on the right, looking at the battery from its long side with the terminals closest to you.

### Can I fit the Fulmen FK800 if my car came with an AGM battery?

Only if the FK800 is AGM. A car that leaves the factory with AGM must always run AGM; an EFB in its place will not last and may trigger dashboard warnings.

## Other options if you are unsure about the FK800

- [Other start-Stop batteries (AGM and EFB)](https://bateriasonline.es/en/start-stop-batteries-agm-efb)
- [Full Fulmen catalogue](https://bateriasonline.es/en/fulmen-batteries)
- [Tudor TK720](https://bateriasonline.es/en/tudor-tk720) · 72 Ah, 760 A, 278×175×190 mm
- [Exide EK720](https://bateriasonline.es/en/exide-ek720) · 72 Ah, 760 A, 278×175×190 mm

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*bateriasonline.es — Batteries and accessories · 2026-11-10*