Why does input wattage reduce significantly (& why the unit gets hot) when it approaches a full charge?

As with all lithium-ion batteries, the recharging process produces a high wattage input during the fast charger phase so the battery cells can reach a high temperature of up to 140 degrees F. It is recommended that you place your power station on a dry cool non-carpeted surface such as tile or wood floors. As it approaches close to 80-90%, it will begin to trickle charge to prevent any overheating causes to the battery. This is a very normal process and proves that your unit is functioning properly.