# Start-Stop battery Fulmen FK508 12V 50Ah 800A AGM ![Start-Stop battery Fulmen FK508 12V 50Ah 800A AGM](https://baterias.com/3751-home_default/battery-fulmen-fk508-12v-50ah-800a.jpg) > Fulmen FK508 Start-Stop battery 12V 50Ah 800A AGM. Dimensions 260×173×206 mm. Built for Start-Stop and regenerative braking: more cycles and fast recharge. **Category:** [Car batteries equipped with start stop system](https://baterias.com/gb/car-batteries-equipped-with-start-stop-system) → [Fulmen](https://baterias.com/gb/fulmen) - **Canonical URL**: https://baterias.com/gb/battery-fulmen-fk508-12v-50ah-800a - **Language**: en-GB - **Brand**: Fulmen - **Reference**: BCOM-FULMEN-FK508 - **EAN**: 3661024046442 - **MPN**: FK508 - **Last updated**: 2026-10-28 - **Stock**: Out of stock ## Technical specifications | Feature | Value | |---|---| | Brand | FULMEN | | Reference | FK508 | | Model | FULMEN AGM | | Voltage (V) | 12 V | | Largo | 260 mm | | Ancho | 173 mm | | Alto | 206 mm | | Peso | 17.5 kg | | Tecnología | AGM | | EAN | 3661024046442 | | Terminal layout | 9 | | Terminal type | 1 | | Hold down | B07 | | Cold cranking amps (EN) | 800 A | | Capacity (C20) | 50 Ah (c20) | | Case type | G34 | ## Quick description **Fulmen FK508 12V 50Ah 800A** is a dedicated Start-Stop battery with AGM/EFB technology. Withstands intensive cycling at traffic-light stops (hundreds of cranks per day), recharges quickly while driving and keeps comfort loads alive during long idle periods. ## Why this Start-Stop battery? - **Designed for Start-Stop** built for the intensive cycling of modern cars - **2 to 3 times longer life** vs fitting a cheap conventional battery - **Fast recovery** recharges in minutes once the engine is running 🔌 Voltage 12 V ⚡ Capacity 50 Ah C20 🔋 Cold cranking 800 A EN-1 📏 Dimensions 260×173×206 mm ⚙️ Technology AGM ⚖️ Weight 17,5 kg 🏷️ Model FULMEN AGM ## Description ## Start-Stop battery Fulmen FK508 50Ah 800A 12V 12*V* Voltage 50*Ah* Capacity 800*A* Cold cranking 17.50*kg* Weight Designed for cars with Start-Stop, regenerative braking and heavy electrical loads, the **Fulmen FK508** combines **50 Ah** and **800 A** of cold cranking current (EN) with AGM construction able to withstand hundreds of starts a day. It measures 260 × 173 × 206 mm, the format sought by anyone replacing a 50 Ah battery in Start-Stop cars. - Withstands hundreds of starts a day without degrading. - AGM technology: absorbed electrolyte, no spills, can be mounted at an angle. - Up to three times the cycles of a conventional battery. - Compatible with regenerative braking and energy management (BMS). ### What the Fulmen FK508 is for In Start-Stop cars the battery works far harder than in a conventional car; the Fulmen FK508 is built for that intensive cycling and to recharge quickly on the move. Check that it matches your current battery in dimensions, terminals and hold-down: this reference has a weight of 17.50 kg, 1 terminals and B07 hold-down. ### Size, terminals and hold-down of the Fulmen FK508 The Fulmen FK508 is made in the 260 × 173 × 206 mm format and weighs 17.50 kg. It uses a B07 hold-down and 1 terminals, the system that anchors and connects it in the vehicle. For a direct replacement, the current battery tray must accept these dimensions and the same terminal layout; otherwise adapters will be needed or the hold-down will change. ### Technology inside the Fulmen FK508 Fulmen builds the FK508 to the same standards as the rest of its catalogue; what changes between references is capacity, format and terminal position. In an AGM battery the electrolyte is absorbed in glass-fibre separators: there is no free liquid, it cannot spill and it can be mounted at an angle. That construction lowers internal resistance, speeds up recharging and multiplies cycle life compared with a conventional battery. ### Fulmen: the maker behind the FK508 With more than a century of history, Fulmen offers complete ranges for cars, trucks, motorcycles and leisure with the industrial quality of the Exide group. At baterias.com we work directly with the manufacturer or its official distributor: real stock, brand-new product and official warranty. ### Manufacturer's warranty The Fulmen FK508 comes with the **manufacturer's official warranty**. To keep it valid, always fit the same technology as the original battery (AGM or EFB) and register the replacement if your vehicle requires it. ### Usage and maintenance tips In a Start-Stop car the battery is controlled by the ECU; after replacing it, the new battery may need to be registered so the system adjusts charging. If the vehicle only does very short trips, a periodic maintenance charge with an AGM/EFB-compatible charger greatly extends its life. ### Delivery times 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. ## Frequently asked questions ### Is the Fulmen FK508 an AGM battery and what are the benefits of AGM? Yes. AGM (Absorbent Glass Mat) technology, 50 Ah and 12 V: sealed lead-acid, with the electrolyte held in glass fibre. It tolerates heat better and handles more cycles than a conventional battery, which is why it is the required technology with advanced Start-Stop and regenerative braking. ### Is the Fulmen FK508 battery suitable for Start-Stop? Yes, the AGM technology of the FK508 is built for Start-Stop. AGM batteries support advanced Start-Stop and regenerative braking thanks to their higher cycle count. Registering it via OBD is advisable on most modern cars (the alternator then applies the optimum profile), but it works from the start. The general recommendation is EFB for basic Start-Stop and AGM where there is regenerative braking (it handles more cycles), unless the car manufacturer says otherwise. ### What should I bear in mind when fitting this Start-Stop battery? Our blog guide covers it in detail; if the owner's handbook describes a different procedure, follow the manufacturer. Tool: a 10 mm spanner. Time: 15-30 minutes on almost every car, and up to double if the battery is not under the bonnet but in the boot or under a seat. The right order: engine off and key out; disconnect the negative (−) first, then the positive (+); release the hold-down clamp, lift out the old battery and seat the new one in the same position, keeping the polarity; reconnect the positive (+) first and the negative (−) last. If the car has Start-Stop or BMS: a) the technology must match the original (AGM or EFB) or be higher, because a conventional battery would fail within months; b) undo the negative cable at its nut, leaving the IBS sensor in place; c) it is advisable to register the battery via OBD so the alternator applies the proper charging profile. ### What is the service life of the FK508 model? There is no exact figure: for a battery such as the Fulmen FK508 (AGM), a reasonable guide is 5 to 8 years in mild-climate car use with Start-Stop. Many factors play a part: how it is used (lots of short trips, for example), temperature (cold makes every start harder and intense heat evaporates the electrolyte), the condition of the alternator and charging system, power drawn with the engine off and maintenance, as well as the type of car and whether it has Start-Stop. ### What are the dimensions of the Fulmen FK508 battery? Measure your car's battery tray first; if the battery exceeds it by even a millimetre, the hold-down clamp may not close. Length × width × height: 260x173x206 mm. Height is measured to the top of the terminals. Hold-down: B07. ### Is the FK508 valid for my vehicle? For your own vehicle: type your number plate into the finder (DGT/DVLA/KBA identify model and engine), check the "Compatible vehicles" tab below, listing vehicles verified by our technical team, or message us on WhatsApp with make, model, engine and year; we reply during business hours (Mon–Fri 10:00–13:30 and 16:30–18:00 (Spanish time, CET)). If our table and the car handbook disagree, go with what the manufacturer says. ### What are the equivalents of the FK508 model? Interchangeable means the same dimensions, same polarity, same Ah and same CCA; for the FK508, 50 Ah (800 A cranking). See the "Equivalents" section of this page for the recommended options at the same performance level. Mind the technology: in Start-Stop cars an EFB is not swapped for a conventional battery. ### Fulmen FK508 or Tudor TK508: which one to choose? The Tudor alternative that fits where the FK508 goes, with the same polarity. Compared with the FK508 it has the same Ah and cranking power. It costs €142.60 more. A straight swap with nothing to adapt; the difference is the price and the brand you prefer. ### Fulmen FK508 or Exide EK508: which one to choose? Same case and same fitting as the FK508, from Exide. Compared with the FK508 it has the same Ah and cranking power. It costs €140.50 more. If you want to save or the FK508 is out of stock, it is the safe alternative: same dimensions, same polarity and official warranty. ### Why choose AGM instead of EFB for my Start-Stop car? The Fulmen FK508 has a capacity of 50 Ah. Many more charge/discharge cycles than a conventional battery and no leaks: that is what AGM technology brings, with the electrolyte absorbed in glass fibre. For regenerative braking systems such as BMW EfficientDynamics, Mercedes Eco, Audi MHEV, Land Rover ECO or Volvo i-Stop, AGM is the recommendation; it also copes better than an EFB with tilting, vibration and extreme temperatures. ### Is there anything to do after replacing a Start-Stop battery? The alternator detects the new battery and adapts the charge automatically, so on most cars it is not compulsory. Even so, it is advisable to register it via OBD so charging is optimum from the first minute and the battery lasts longer, particularly on BMW, Mercedes, Audi, Volvo or Land Rover, with more sophisticated BMS. Any workshop with an OBD scanner does it in a few minutes; DIY, with VCDS or Carista (VAG group), Bimmercode (BMW) or iCarsoft. Even if you do not register the Fulmen FK508, the car will start correctly; the profile adjusts within a few days. ## Equivalent batteries - [TUDOR TK508](https://baterias.com/gb/battery-tudor-tk508-50ah-800a) - [EXIDE EK508](https://baterias.com/gb/battery-exide-ek508-12v-50ah-800a) ## Technical team (editorial authorship) The FAQs, guides and comparisons on this site are reviewed by the baterias.com technical team — automotive battery specialists since 2012. → https://baterias.com/gb/technical-team --- *baterias.com — Automotive batteries · 2026-11-08*