Clarify permissions documentation (#223)

* Clarify permissions documentation

* Formatting

Author: RonvanderPlas

docs/v2/batteries.mdx

@@ -57,7 +57,8 @@ Mode `standby` is exactly the same as mode `zero` with both charging and dischar
 
 - When switching to `standby` mode, the `permissions` field will be set to an empty array `[]`.
 - When adding a permission to the `permissions` field while in `standby` mode, the mode will automatically switch to `zero`.
-- `zero` mode with both permissions allowed is the same as the default `zero` mode.
+- `zero` mode with both permissions **allowed** is the same as the default `zero` mode.
+- `zero` mode with both permissions **disallowed** is the same as `standby` mode, therefore mode will automatically switch to `standby`.
 
 ## Examples