The British Rail BEMU was an experimental two-car battery electric multiple unit (BEMU), converted from the prototype Derby Lightweight Diesel multiple units.
The train was powered by many lead-acid batteries , and was used on the Deeside Railway from Aberdeen to Ballater in Scotland from April 1958 until it was finally withdrawn in December 1966. The North of Scotland Hydro-Electric Board initiated the design and was a joint sponsor. The board promised to supply power at three farthings per unit for a fixed two-year period. It provided an 11kV supply to a charger at Aberdeen's platform 1 and a 6.6kV supply to a charger at Ballater.
The train then spent a short time in storage at Inverurie Works, and at Hyndland Shed in Glasgow, before being transferred to departmental use as test train "Gemini" (or "Laboratory 16") for use at the Railway Technical Centre, at Derby.
Following a full refurbishment, 'Gemini' entered use in the now-familiar Research department red and blue colourscheme, and was instrumental in testing the latest developments of the Automatic Train Protection signalling system, making regular appearances on the Mickleover test track, as well as further afield near Swindon. Following withdrawal, the unit has returned to its native Scotland where it lives on in preservation.
