Fulmen FK600 · Start-Stop battery 60Ah 680A AGM

Yes: the FK600 from Fulmen uses AGM (Absorbent Glass Mat) technology, a sealed lead-acid battery whose electrolyte soaks a glass-fibre mat. 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.

AGM batteries support advanced Start-Stop and regenerative braking thanks to their higher cycle count. The Fulmen FK600 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. 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.

Our blog guide covers it in detail; if the owner's handbook describes a different procedure, follow the manufacturer. On most cars it is a 15-30 minute job needing only a 10 mm spanner (up to twice as long when the battery is under a seat or in the boot). 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 (positive on the right), keeping the polarity; reconnect the positive (+) first and the negative (−) last. 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.

As a rough estimate, the Fulmen FK600 typically lasts 5 to 8 years in mild-climate car use with Start-Stop; it is a guide figure, not a guaranteed period. 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 242×175×190 mm in length × width × height, with the terminals included in the height; that is the European L2 case size.

Polarity of the Fulmen FK600: positive on the right. 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.

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 FK600, 60 Ah (680 A cranking). 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.

It is the verified Varta equivalent for the FK600 tray. Compared with the FK600 it has the same Ah and cranking power. It costs €107.40 more. Decide by price, brand preference and availability: both fit and crank the same.

The Exide alternative that fits where the FK600 goes, with the same polarity. Compared with the FK600 it has 2 Ah more. It costs €93.30 more. A straight swap with nothing to adapt; the difference is the price and the brand you prefer.

The Fulmen FK600 has a capacity of 60 Ah. 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. 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.

Advisable, yes; essential, on most cars, no. Registering it via OBD makes the alternator charge with the optimum profile from the first minute and extends battery life, which matters most on brands with sophisticated BMS such as BMW, Mercedes, Audi, Volvo or Land Rover. Without registration there is no starting problem: the alternator adjusts the profile within a few days. A workshop only needs an OBD scanner and a few minutes. DIY apps: VCDS / Carista (VAG), Bimmercode (BMW), iCarsoft.