You can refund your remaining balance at any time as long as you don't have a charging session in progress.
Your balance can be refunded through the Hypercharge app by following these steps:
From any page in the app, tap the Account icon in the bottom right.
Tap the "..." icon to the right of your current account balance
Select "Refund all balance"
Swipe the "Refund" slider to confirm
You will see a "Success" confirmation when your refund has been processed. Refunds are processed immediately by Hypercharge, but it may take several days for refunded funds to be returned to you by your bank.