I just went to connect the BM2 to the car's 12v battery. My notes from the forum said - you only need to disconnect the negative. Then it 'hit' me! Surely you can only connect the + and - BM2 tabs by disconnecting each terminal, even if only singly? I could take off the negative as advised, and reconnect it after slotting in the tab - but I still have to remove the +ve.