Battery discharge

Hi how do I stop battery to discharge and only use cheap tariff at night time?
Thanks

You need to give us more information what is going on.

But, in simple terms, you need to make sure that your battery is set to ECO mode always. You can do that from the online portal.
Then you want to set TIMED CHARGE, if/when you want the battery to charge from the grid (if you are on Octopus Go or similar). In the settings, you want to give start time (00:30 for OctGO) and end time (04:30). Set the maximum % for the battery to charge, usually 100%. But you can vary that with your daily usage or maybe anticipate solar generation from a clear-day forecast.