Fulmen FK1050 · Start-Stop battery 105Ah 950A AGM

Yes: the FK1050 from Fulmen uses AGM (Absorbent Glass Mat) technology, a sealed lead-acid battery whose electrolyte soaks a glass-fibre mat. Compared with a conventional battery it withstands more charge/discharge cycles and handles heat better; it is the required technology for cars with advanced Start-Stop and regenerative braking.

Yes: being AGM, the Fulmen FK1050 is designed for Start-Stop cars. AGM batteries support advanced Start-Stop and regenerative braking thanks to their higher cycle count. Basic Start-Stop: EFB. Start-Stop with regenerative braking: AGM, which withstands more cycles. Check the handbook for the technology the car manufacturer requires. Registering it via OBD is advisable on most modern cars (the alternator then applies the optimum profile), but it works from the start.

On cars with Start-Stop or BMS, registering the battery via OBD makes the alternator charge with the correct profile. Mind the IBS sensor on the negative terminal too: loosen the cable nut, not the sensor. And the replacement must be the same technology (AGM or EFB) or higher: a conventional battery fails within months. 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. Steps: 1) switch off and remove the key; 2) find the battery (bonnet, boot or under a seat); 3) undo the negative (−), then the positive (+); 4) remove the clamp and the old battery; 5) fit the new one facing the same way (positive on the right) to match the polarity; 6) connect the positive (+) and finally the negative (−). Our blog guide covers it in detail; if the owner's handbook describes a different procedure, follow the manufacturer.

As a guide, you can expect the Fulmen FK1050 to last 5 to 8 years in mild-climate car use with Start-Stop, although the real figure may be higher or lower. What weighs most: temperature (cold makes starts harder and intense heat evaporates the electrolyte), frequent short trips, the condition of the alternator and charging system, power draw while parked and maintenance, not forgetting the type of car and Start-Stop.

It measures 392×175×190 mm in length × width × height, with the terminals included in the height; that is the European L6 case size. Measure the battery tray before ordering: a one-millimetre difference is enough for the hold-down clamp not to close.

On the Fulmen FK1050, the polarity is positive on the right. If your current battery has its positive on the other side, this one is not suitable without longer cables or a reconfigured system (short-circuit risk). To check, stand the battery in front of you with the terminals nearest you: the positive (+) is the one with the red ring.

Three routes: the "Compatible vehicles" tab on this page, with the vehicles verified by our technical team; your number plate in the finder, from which DGT/DVLA/KBA detect model and engine; and WhatsApp, with make, model, engine and year, during business hours (Mon–Fri 10:00–13:30 and 16:30–18:00 (Spanish time, CET)). The FK1050 typically fits a wide range of European vehicles thanks to its standard DIN case format. In every case, the car manufacturer's specifications (owner's handbook) take precedence.

The "Equivalents" section of this page gathers the recommended options with equivalent performance; remember that in Start-Stop cars an EFB should not be replaced with a conventional battery. Interchangeable means the same dimensions, same polarity, same Ah and same CCA; for the FK1050, 105 Ah (950 A cranking).

It is the verified Varta equivalent for the FK1050 tray. Compared with the FK1050 it has the same Ah and cranking power. It costs €189.30 more. Decide by price, brand preference and availability: both fit and crank the same.

The Varta alternative that fits where the FK1050 goes, with the same polarity. Compared with the FK1050 it has the same Ah and cranking power. It costs €189.30 more. A straight swap with nothing to adapt; the difference is the price and the brand you prefer.

Hence it is recommended for advanced Start-Stop with regenerative braking, such as BMW EfficientDynamics, Mercedes Eco, Audi MHEV, Land Rover ECO or Volvo i-Stop, and it handles tilting, vibration and extreme temperatures better than an EFB. 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 FK1050 has a capacity of 105 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 FK1050, the car will start correctly; the profile adjusts within a few days.