[larsen]

My M750 had an odd fault, similar to yours, the battery going "flat" quickly on layup. Key in, ignition on, dim dash lights. I thought battery, did the tests all ok but had convinced myself that the battery was the issue, changed it, still the same. waste of money, eventually worked out it was the main relay (under the seat) going high resistance internally, opened it up, cleaned the contacts, still the same. Changed it for a new one and, fingers crossed, it solved the issue.