Fulbat AUX14-J Auxiliary AGM · Auxiliary battery 14Ah

Yes: the AUX14-J from Fulbat uses AGM (Absorbent Glass Mat) technology, a sealed lead-acid battery whose electrolyte soaks a glass-fibre mat. It tolerates heat better and handles more cycles than a conventional battery, which is why it is the required technology with advanced Start-Stop and regenerative braking.

Yes, the AGM technology of the AUX14-J is built for Start-Stop. 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.

There is no exact figure: for a battery such as the Fulbat AUX14-J (AGM), a reasonable guide is 5 to 8 years in mild-climate car use with Start-Stop. 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.

The Fulbat AUX14-J takes up 150×87×145 mm (length, width and height, terminals included). Before buying, measure the space in your car: one extra millimetre can stop the hold-down clamp from closing.

It has the positive on the left (polarity). 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). Put it in front of you, terminals towards you: the post with the red ring and the + sign is the positive.

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.

A direct equivalent needs what this AUX14-J offers: 150×87×145 mm, positive on the left, the same Ah and CCA and AGM technology. 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 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. The absorbent glass-fibre mat of an AGM retains the electrolyte, so it cannot leak and withstands considerably more cycles than a conventional battery.

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.