Lowndes was based in London in St Paul’s Churchyard. He established himself as an authority on medical electricity, the use of electricity as a therapy for both disease and injury. His book Observations on Medical Electricity, published in 1787, contained descriptions of a number of cases "in which electricity has either cured the disease, or given great relief.” In 1796 he received a patent for his invention of the ‘Patent Gymnasticon’, an early exercise machine resembling a stationary bicycle, which was designed to exercise the joints, either "in all parts of the body at once, or partially." His will was proved in London on 20 October 1819.