Not normal, but same with mine. Mine stays in the upper half for long time. Then I had half tank going up the mountain pass, then going down I lost 5-10km range every km. Until it did not display any range at all and was red. A bit frightening, but I made it to the next petrol station (with probably still > 6-8 litre in the tank. The tank gauge is really not working on mine. But I have a early software version, hope to get this fixed as well with the update promised for late September.
