I recogniced that the flexshaft was worn out (+rusty). I have changed it with a new, but still there are speed problems. Todays morning with an outside temp. near freezing point, the problem was there from the start. I guess that the temp. is not a issue. (All cables was cold). Have recharged the batteries; Voltage of cells and total (4,20 -4,20 -4,20 ) 12,6. Next step...?? May be the speed-controller?