Fulmen FL550 · Start-Stop battery 55Ah 540A EFB

Yes. The FL550 is an EFB (Enhanced Flooded Battery): flooded lead-acid reinforced with plate additives. It goes into cars with basic Start-Stop (no energy recovery when braking): more cycles than a conventional battery, fewer than an AGM, and cheaper than an equivalent AGM.

Yes, the EFB technology of the FL550 is built for Start-Stop. EFB batteries cover basic Start-Stop (no regenerative braking). Once fitted it is ready to go; registering it via OBD, advisable on most modern models, lets the alternator charge with the optimum 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.

With a 10 mm spanner, swapping in the Fulmen FL550 takes 15 to 30 minutes on most cars; if the battery sits in the boot or under a seat, allow up to twice as long. With the engine stopped and the key removed, always start with the negative (−) terminal, then the positive (+). Free the clamp, swap the battery without turning it round (this one has positive on the right) so the polarity stays the same, and reconnect in reverse: positive (+) first, negative (−) last. Start-Stop or BMS specifics: do not remove the IBS sensor on the negative terminal (just loosen the cable nut); after the swap, register the battery via OBD so the alternator charges with the right profile; and never step down in technology: if the car had AGM or EFB, the new one must be the same or better, as a conventional battery lasts only a few months. Our blog guide covers it in detail; if the owner's handbook describes a different procedure, follow the manufacturer.

There is no exact figure: for a battery such as the Fulmen FL550 (EFB), a reasonable guide is 4 to 6 years in basic Start-Stop car use. 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.

Before buying, measure the space in your car: one extra millimetre can stop the hold-down clamp from closing. The Fulmen FL550 takes up 207×175×190 mm (length, width and height, terminals included), the European L1 case size, with a B13 hold-down.

It has the positive on the right (polarity). Put it in front of you, terminals towards you: the post with the red ring and the + sign is the positive. A change of polarity from the original means longer cables or a reconfigured system and can cause a short circuit: check it before ordering.

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)). The car manufacturer's specifications always take priority over our tables.

Interchangeable means the same dimensions, same polarity, same Ah and same CCA; for the FL550, 55 Ah (540 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.

A technology step up: sealed AGM, with stronger cranking and a noticeably longer life than the FL550 when the car draws a lot of power. Compared with the FL550 it has 5 Ah less. It costs €118.90 more. Choose it if your car required it from the factory or if you want the longest-lasting battery for this size; for normal use without Start-Stop, the FL550 is plenty.

Same case and same fitting as the FL550, from Tudor. Compared with the FL550 it has the same Ah and cranking power. It costs €76.95 more. If you want to save or the FL550 is out of stock, it is the safe alternative: same dimensions, same polarity and official warranty.

Many basic Start-Stop systems (no regenerative braking) come with it from the factory, such as Renault Energy TCe, Peugeot/Citroën PureTech, Fiat MultiAir, Hyundai/Kia ISG and Ford EcoBoost. The EFB (Enhanced Flooded Battery) is a reinforced flooded battery: plates with carbon and polyethylene additives and thicker grids, giving it more cycles than a conventional one; for cycles and deep discharges it still sits below an AGM. Rule of thumb: car with an EFB from new, EFB (AGM is an optional, marginal upgrade); car with an AGM from new, AGM.

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. A workshop only needs an OBD scanner and a few minutes. DIY apps: VCDS / Carista (VAG), Bimmercode (BMW), iCarsoft. Even if you do not register the Fulmen FL550, the car will start correctly; the profile adjusts within a few days.