New to smart meters. Got a few questions

Had a smart meter (electric only) fitted yesterday. The IHD that it came without instructions or batteries and seems to be a Geo Trio ii. It takes 3 AAA batteries by the looks of things but cant tell if it takes rechargeable or alkalines and if there is a built in charger. I read mention about a wifi unit that can plug in the back but mine doesnt seem to have that option. Before pursuing the wifi extra is the Octopus Home Mini a better bet. Though even that seems to be on a long waiting list.