# Auxiliary battery Fulbat AUX9 12V 8.4Ah AGM ![Auxiliary battery Fulbat AUX9 12V 8.4Ah AGM](https://baterias.com/6489-home_default/battery-fulbat-aux9-12v-8-4ah.jpg) > Fulbat AUX9 auxiliary battery 12V 8.4Ah AGM. Auxiliary AGM range. Dimensions 150Γ—87Γ—105 mm, + terminal on the left. Check fitment by plate. **Category:** [Auxiliary Batteries](https://baterias.com/gb/auxiliary-batteries) β†’ [FULBAT](https://baterias.com/gb/fulbat) - **Canonical URL**: https://baterias.com/gb/battery-fulbat-aux9-12v-8-4ah - **Language**: en-GB - **Brand**: FULBAT - **Reference**: BCOM-FULBAT-AUX9 - **MPN**: AUX9 - **Stock**: Out of stock ## Technical specifications | Feature | Value | |---|---| | Brand | FULBAT | | Model | FULBAT Auxiliary AGM | | Voltage (V) | 12 V | | Largo | 150 mm | | Ancho | 87 mm | | Alto | 105 mm | | TecnologΓ­a | AGM | | Terminal layout | Positive left | | Capacity (C20) | 8.4 Ah | | Capacity (C10) | 8 Ah (c10) | ## Quick description **Fulbat AUX9 12V 8Ah** is an auxiliary battery: it supports the Start-Stop system and on-board electronics during stops, without draining the main battery. ### Why this auxiliary battery? - **Designed for Start-Stop** built for the intensive cycling of modern cars - **2 to 3 times longer life** vs fitting a cheap conventional battery - **Fast recovery** recharges in minutes once the engine is running πŸ”Œ Voltage 12 V ⚑ Capacity 8 Ah C20 πŸ“ Dimensions 150Γ—87Γ—105 mm βš™οΈ Technology AGM 🧭 Polarity Positive on the left 🏷️ Model FULBAT Auxiliary AGM ## Description ## Auxiliary battery Fulbat AUX9 8.4Ah 12V 12*V* Voltage 8.4*Ah* Capacity The **12 V**, **8.4 Ah** **Fulbat AUX9** auxiliary battery with AGM technology powers the auxiliary network of cars with advanced Start-Stop and heavy electronics. It measures 150 Γ— 87 Γ— 105 mm and the positive terminal on the left, the format sought by anyone replacing a 8.4 Ah battery in vehicles with an auxiliary battery. - Stabilises the onboard network voltage. - AGM technology: absorbed electrolyte, no spills, can be mounted at an angle. - Maintenance-free. - Sealed AGM: safe when installed in the cabin. ### What the Fulbat AUX9 is for As an auxiliary battery, the Fulbat AUX9 works alongside the main one; replace it when the vehicle reports a fault in the support network. ### Size, terminals and hold-down of the Fulbat AUX9 It has external dimensions of 150 Γ— 87 Γ— 105 mm. The positive terminal on the left decides which side the cables end up on: it is the detail that causes most buying mistakes, so check it before ordering. Checking the three dimensions and the terminal position before buying avoids the most common mistake when replacing a battery. ### Why choose Fulbat batteries Fulbat has manufactured in France since 1978 and specialises in motorcycles and light vehicles. Its catalogue is short and clear, covers almost the whole fleet and works only with sealed, leak-free batteries. All the Fulbat batteries in our catalogue are genuine product, recently manufactured and covered by the manufacturer's warranty. ### Technology inside the Fulbat AUX9 The AUX9 is one of the Fulbat references for this type of use; it shares the same manufacturing and quality-control criteria as the rest of the brand's catalogue. AGM means the acid is held in a glass mat instead of floating free. That is why the battery can be installed in the cabin without gases, survives more cycles and recovers its charge quickly. ### Usage and maintenance tips Replace it with the same technology and capacity as the original. The auxiliary battery works alongside the main one: if a support-network fault warning appears, check both. ### Manufacturer's warranty The Fulbat AUX9 comes with the **manufacturer's official warranty** against manufacturing defects. If it fails through a defect within the warranty period, we replace it at no cost to you. ### Shipping, delivery and returns Orders placed **before [[ks:cutoff]]** with the battery in stock ship the same day. Delivery in mainland Spain and Portugal takes 24-48 working hours; for the Balearic and Canary Islands and the rest of the European Union allow 3 to 5 working days. You have **[[ks:return_days]] days** to return an unused battery; in mainland Spain and Portugal collection is free. We email you the tracking number as soon as the parcel ships. ## Frequently asked questions ### How do I fit the AUX9 model in my car? In most cars it fits in 15-30 minutes with a 10 mm wrench; if the battery is under the seat or in the boot the time can double. See the step-by-step guide on this page. Quick summary: 1) switch off the engine and remove the key; 2) locate the original battery (engine bay, boot or under seat); 3) disconnect the negative (βˆ’) terminal first, then the positive (+); 4) loosen the hold-down clamp and remove the old battery; 5) fit the new one in the same orientation β€” match the polarity shown on the product sheet; 6) connect the positive (+) first, then the negative (βˆ’). On cars with Start-Stop or BMS, register the battery via OBD so the alternator applies the correct charging profile. ### How long does the Fulbat AUX9 battery last? Expected lifespan of the Fulbat AUX9 is 4 to 7 years in regular use (depends on technology and climate). In cold regions it drops slightly due to cold-start stress; in very hot regions it also drops because of electrolyte evaporation. To extend its life: avoid deep discharges (headlights on with engine off), have the alternator checked yearly, and keep the battery clean and properly secured. ### What are the dimensions of the Fulbat AUX9 battery? Dimensions (length Γ— width Γ— height) are 150Γ—87Γ—105 mm β€” also written as 150x87x105 mm β€” following the European DIN standard. Always measure the space in your car before buying: even one extra millimetre can prevent the hold-down clamp from closing. The height shown includes the terminals. ### Will the Fulbat AUX9 battery fit my car? Three options to confirm: 1) enter your number plate in the finder (DGT/DVLA/KBA auto-detect your model and engine); 2) check the "Compatible vehicles" tab on this page, where we list every vehicle verified by our technical team; 3) if you cannot find your model, message us on WhatsApp with brand, model, engine and year β€” we reply during business hours (Mon–Fri 10:00–13:30 and 16:40–18:00 (Spanish time, CET)). The AUX9 typically fits a wide range of European vehicles thanks to its standard DIN case format. ### Which interchangeable batteries are there for this one? Directly interchangeable batteries (same dimensions, same polarity, same Ah and CCA) are the OEM equivalents from leading brands: Bosch, Tudor, Exide and, depending on the model, Banner or Yuasa. Exact equivalence depends on technology β€” an EFB cannot be replaced with a conventional battery in Start-Stop cars. See the "Equivalents" section to view recommended options at the same performance level. ## Technical team (editorial authorship) The FAQs, guides and comparisons on this site are reviewed by the baterias.com technical team β€” over 25 years of experience validating automotive batteries. β†’ https://baterias.com/gb/technical-team --- *baterias.com β€” Automotive batteries Β· 2026-10-03*