Have found a slightly inconvenient work around solution. In settings, apps,all - find exchange services and disable the app accept the disfunction warning. I do this when not on external power. It means that while disabled you will not get any syncing or receive any emails. You can manually get emails by temporarily re-enabling the app. I know this is not brilliant but i have just been out for 3 hours and only used 4% of the battery.
When i am back on power i re-enable the app (it appears right at the bottom of the list of all apps) and everything goes back to normal.