The Battery Electric Multiple Unit was an experimental two-car Multiple unit, built at the same time and in the same style as the prototype Derby Lightweight Diesel multiple units.

It was powered by large lead-acid batteries and was used on the Royal Deeside line from Aberdeen to Ballater in Scotland from 1958. The unit was equipped with a new type of battery in the early 1960s but subsequently suffered a series of small fires in the battery areas and was withdrawn from service. It is believed to have returned to use for a period before closure of the line in 1966.

It 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 Lab 16) for use at the Railway Technical Centre at Derby. It lasted in this role until it was withdrawn in 1984, and was eventually bought for preservation at the proposed West Yorkshire Transport Museum. The museum placed it on loan to the East Lancashire Railway who restored it and used it on services. The museum went into liquidation and the unit was purchased by the Royal Deeside Railway in 2001 and is now back in Scotland. Details are as follows: