Fulmen FK111 Start-Stop Auxiliary · Battery 11Ah 150A AGM

Yes, it is AGM. In an AGM battery such as the FK111, the electrolyte is not free but absorbed in a glass-fibre mat inside a sealed lead-acid battery. It is the technology required by cars with advanced Start-Stop and regenerative braking. It withstands more cycles than a conventional battery and copes better with heat.

Yes. It is a AGM battery of 11 Ah, designed for vehicles with Start-Stop. AGM batteries support advanced Start-Stop and regenerative braking thanks to their higher cycle count. It works once fitted; on most modern cars, registering it via OBD is advisable so the alternator applies the optimum 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.

Estimated lifespan of the Fulmen FK111: 5 to 8 years in mild-climate car use with Start-Stop. Treat it as an approximate guide, as every case is different. It can vary considerably with usage (short or long journeys), temperature, the condition of the alternator and charging system, power drawn with the engine off and maintenance, plus the car itself and Start-Stop. Cold demands more at every start and intense heat evaporates the electrolyte.

Measure the battery tray before ordering: a one-millimetre difference is enough for the hold-down clamp not to close. It measures 150×90×130 mm in length × width × height, with the terminals included in the height.

The FK111 has the positive on the left: that is its polarity. Face the battery with its terminals nearest you and see which side the positive post (+, red ring) is on. Compare it with the battery you are replacing: if it does not match, cables must be lengthened or the system reconfigured, with a risk of short circuit.

Not sure? Try your number plate in the finder (DGT/DVLA/KBA detect model and engine) or the "Compatible vehicles" tab, checked by our technical team; if your car is not there, send us make, model, engine and year on WhatsApp and we will reply during business hours (Mon–Fri 10:00–13:30 and 16:30–18:00 (Spanish time, CET)). In every case, the car manufacturer's specifications (owner's handbook) take precedence.

Interchangeable means the same dimensions, same polarity, same Ah and same CCA; for the FK111, 11 Ah (150 A cranking). 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.

The Exide alternative that fits where the FK111 goes, with the same polarity. Compared with the FK111 it has the same Ah and cranking power. It costs €33.60 more. A straight swap with nothing to adapt; the difference is the price and the brand you prefer.

It is the verified Tudor equivalent for the FK111 tray. Compared with the FK111 it has the same Ah and cranking power. It costs €169.70 more. Decide by price, brand preference and availability: both fit and crank the same.

It is the recommended choice for advanced Start-Stop with regenerative braking (BMW EfficientDynamics, Mercedes Eco, Audi MHEV, Land Rover ECO, Volvo i-Stop) and copes better than an EFB with tilting, vibration and extreme temperatures. AGM means Absorbent Glass Mat: the electrolyte soaks a glass-fibre mat (no spills), and an AGM battery lasts many more cycles than a conventional one. The Fulmen FK111 has a capacity of 11 Ah.

It is not strictly necessary on most cars, because the alternator detects the change and adapts the charge. The advisable step is to register it via OBD: the charging profile is optimum from the first minute and the battery lasts longer, especially on brands with sophisticated BMS (BMW, Mercedes, Audi, Volvo, Land Rover). Any garage with an OBD scanner can do it in a few minutes. If you prefer to do it yourself: VCDS / Carista (VAG), Bimmercode (BMW) or iCarsoft. Even if you do not register the Fulmen FK111, the car will start correctly; the profile adjusts within a few days.