SS Thistlegorm also contains several “outside” trolley accumulators. The trolleys were used by the RAF and contained a number of batteries. The trolley has a thick cable that was plugged into aircraft to conserve their battery power on the ground..
Many thanks to the Aircraft Restoration Company engineers who helped me with these identifications, especially Colin, Mike and Smudge.
The example shown above is in the Malta Aviation Museum - the image also is a link to their web site. The picture (which comes from their web site shows both the cable and the structure of the trolley). Below is a Trolley Accumulator half-buried under Blenheim tail planes - note plug:
