Per the opening post "the heavily drained battery was initially charging at over 20 Amps, and after 15 miles only dropped to 11 Amps" I think it would take a very long drive to fully charge the battery and see a zero charge rate. After a heavy use it always seems to initially charge at quite a high current then quickly reduce. The camper is presently sitting on the drive with it's usual smart charger connected via an otherwise unused towbar connector. . This method of charging is very slow but I gather is the "kindest" way charge a battery. Just waiting now for the (slightly overpriced) ignition switch to arrive.