Power Balance affects the power and plasma you earn in battle, as well as the quality/quantity of loot received from chests, Duties, and things like that. If you die or run from battle, you lose Power Balance which temporarily diminishes these bonuses. I think that’s a good way to punish players for dying/running without directly taking anything away from them. This mechanic will be used for other content in the future.
Power Balance can never drop below 20%, so when you used the portal, is it possible that you had only 20% Power Balance at that time?