My Surface Pro 2 is 4 years old. All of a sudden my battery discharges as soon as I take it off the docking station. I’ve checked that all my updates are current. I’ve run the trouble shooter on the battery and it says it’s okay. When it’s docked and on the charger it says 100% charge. It immediately discharges and shuts down when I take it off. Help! I can’t take it to meetings unless I can find a plug it. I can’t even find a portable charger. Thanks! Joan T.