[v2.3-stable] Changed default value of `max_charge_groups` to 0
Backport version of !788 (merged), setting the default value of max_charge_groups
to 0 (i.e. maintaining previous behaviour of no maximum number of groups as default).
Backport version of !788 (merged), setting the default value of max_charge_groups
to 0 (i.e. maintaining previous behaviour of no maximum number of groups as default).