Fulmen FK131 Start-Stop Auxiliary · Battery 13Ah 200A AGM

Yes, it is AGM. In an AGM battery such as the FK131, the electrolyte is not free but absorbed in a glass-fibre mat inside a sealed lead-acid battery. Its advantages: more charge/discharge cycles than a conventional battery and better heat tolerance. It is also required in cars with advanced Start-Stop and regenerative braking.

AGM batteries support advanced Start-Stop and regenerative braking thanks to their higher cycle count. The Fulmen FK131 is AGM, so yes, it is designed for Start-Stop cars. It needs nothing to work, though on most modern cars registering it via OBD is advisable so the alternator adjusts its charging profile. As a rule: EFB for basic Start-Stop, AGM when there is also regenerative braking (more cycles); in any case, what the car manufacturer specifies.

As a rough estimate, the Fulmen FK131 typically lasts 5 to 8 years in mild-climate car use with Start-Stop; it is a guide figure, not a guaranteed period. Actual lifespan varies with climate (cold starts, heat evaporating the electrolyte), with usage and short journeys, with the condition of the alternator and charging system, with power draw while parked and with maintenance; the type of car and Start-Stop also count.

Check the room available in your car, because a single millimetre too much can stop the clamp from closing. Its dimensions are 150×90×145 mm, also written 150x90x145 mm; the height already includes the terminals.

Polarity of the Fulmen FK131: positive on the left. It must match your current battery: reversed polarity means lengthening cables or reconfiguring the system, with a risk of short circuit. Seen from the front, terminals towards you, the positive (+) is the post with the red ring.

The quickest way is to enter your number plate in the finder: DGT/DVLA/KBA detect model and engine. You can also look at the "Compatible vehicles" tab, verified by our technical team, or send us make, model, engine and year on WhatsApp; we answer during business hours (Mon–Fri 10:00–13:30 and 16:30–18:00 (Spanish time, CET)). Always cross-check with what the car manufacturer states in the owner's handbook.

Not just any technology will do: an EFB cannot be replaced with a conventional battery in Start-Stop cars. The "Equivalents" section further down lists the recommended alternatives. Interchangeable means the same dimensions, same polarity, same Ah and same CCA; for the FK131, 13 Ah (200 A cranking).

Same case and same fitting as the FK131, from Exide. Compared with the FK131 it has the same Ah and cranking power. It costs €62.20 more. If you want to save or the FK131 is out of stock, it is the safe alternative: same dimensions, same polarity and official warranty.

The Tudor alternative that fits where the FK131 goes, with the same polarity. Compared with the FK131 it has the same Ah and cranking power. It costs €63.60 more. A straight swap with nothing to adapt; the difference is the price and the brand you prefer.

In an AGM (Absorbent Glass Mat) battery the electrolyte is held in a glass-fibre mat: no spills, and many more charge/discharge cycles than a conventional battery. Compared with an EFB it resists tilted positions, heavy vibration and extreme temperatures better, and it is the recommended option where there is regenerative braking (BMW EfficientDynamics, Mercedes Eco, Audi MHEV, Land Rover ECO, Volvo i-Stop). The Fulmen FK131 has a capacity of 13 Ah.

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 FK131, the car will start correctly; the profile adjusts within a few days.