I had thought about asking a speedo manufacturer to put 3.5mm barrels or even smaller for 12th scale ,right in the speedo at the outputs, built them right into the case . You would never have to heat the most expensive piece of equiptment up again. Well, atl east with a soldering iron anyways. the connectors could be heat shrunk and or fastened down . Replacing wires could be as easy pie and the speedo could stay in the car durring the opperation. then you could use whatever battery you want . And no soldering to speedos and especially ,, NO DEANS CONNECTOR!