The best way to ensure that the battery does not get depleted is to remove it entirely from the PowerShell™ and store it separately after it has been fully charged. There is no way to turn off the flow of charge from the battery to the Z1 if they are both in the PowerShell™ together.
Additionally, the PowerShell™ itself will draw a small amount of charge from the battery and drain it within 2-3 days.
We suggest that your battery be fully charged every few weeks, if you are not using your battery, to maintain a charge.
Note: Make sure that your battery is fully charged before disconnecting it from the PowerShell™. When you have 4 solid bars that are no longer flashing, the battery is 100% charged.