Most key fob 'faults' are flat batteries. Here's exactly which battery your car takes.
VAG (VW, Audi, Skoda, SEAT)
CR2032 for most flip keys and smart keys 2015+. Older flip keys use CR1620 or CR2025.
BMW
Smart keys from 2009+ are inductive-charging — no battery to change. Older 'comfort access' fobs use CR2450.
Mercedes
Smart keys typically use 2x CR2025 stacked. Older flip keys use CR2025.
Ford, Vauxhall, Toyota, Honda
Almost universally CR2032. A handful of premium models use CR2450.
Land Rover / Range Rover
CR2032 on most smart keys. Replace in pairs if you have two keys — the spare drains faster than people think.
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