I have just been trying to find an on-line copy of the manual for the Nuprol SM-4 charger. It's no longer available on the Nuprol web site, but I came across a link about a safety recall from September last year: https://ec.europa.eu/consumers/cons...317/18&exclude_search_term=0&search_year=2018 The problem is that "The electrical insulation is inadequate." The risk is that "As a result, accessible parts of the product could become live. The user could receive an electric shock from them. The product does not comply with the requirements of the Low Voltage Directive and the relevant European standard EN 60335." The recommended action is "Destruction of the product" I'm going to try and find out from Nuprol about getting a replacement.