The battery location on a Ford Transit T280 van depends slightly on the year of manufacture and specific trim level, but it's generally located
under the bonnet (hood) in the engine compartment, similar to most cars. It's usually on the
nearside (left-hand side in the UK, right-hand side in the US), although this isn't guaranteed across all models.
To be absolutely sure, check your vehicle's owner's manual. It will have a diagram showing the exact location of the battery.