Max hero energy vs Max energy cost to battle

Did you set max energy cost for a single battle? If yes, what is it?

I’m asking this question because Hero’s max energy is set to 500, and how can you make a single battle costs more than 500, even though our opponents were out numbered?
We started a war with 2 vs 10 and we have about 10 more members round the area to join later. We are all over the world / different time zones. The idea was to start a war first because the event time is running out, buy some time and prevent from supreme victory, then have other members join the war later. It’s 2 vs 10 and a single war costs 657 when a hero’s max energy is 500? Really? Can’t even do a single battle! Not many alliances can move 10 soldiers at the same time.