Mobile Media has so far installed 10 of its vans with lighting, but plans to re-engineer the remainder.
David Pounds, a director at Mobile Media, said that, while installing the electricity for the vans is a trade secret, "it took a lot or research and development to get electricity powerful enough and to meet the required safety standards".
Mobile Media installed its fleet of ad bikes and scooters with back-lighting a few years ago, which Pounds said was an easy job.
However, he said that building illuminations into the vans was "10 times as complicated" and required a special watertight snap-on frame for the vinyl posters.
The basic vans are supplied by Hendy Trucks. The chassis are extended and the lighting installed at Mobile Media's site in Bournemouth.
Mobile Media's vans were recently hired by Cheshire police force for a campaign targeting hotspots of alcohol-fuelled violence.