Hyundai batteries follow two size families. Smaller and older models tend to use compact Japanese-pattern sizes, while many recent SUVs such as the Tucson and Santa Fe take European-pattern cases. The label on the old battery is the safest guide, and a photo of it on WhatsApp is enough to bring the right one. Many recent models have a battery sensor on the negative terminal, which stays on the car and needs no coding.
Versions with Idle Stop and Go switch the engine off at traffic lights, and they need the AGM or EFB battery they were built with to survive hundreds of extra starts. A standard battery in its place fails early. Hybrids need a closer look. Some, the Ioniq Hybrid among them, have no separate lead-acid 12V battery at all. A lithium unit is built into the hybrid pack, with a 12V BATT RESET button on the dash. The technician checks for this first.