Hyper-Converge Infrastucture (HCI) is virtualisation technology, it virtualises what would otherwise be physical components of your infrastructure (e.g. servers, storage, networking etc) creating a software based environment rather than a physical one. Also worth noting that this technology still needs to run physical servers.
The way I would re-charge it is by allocating the cost to all the components that are being virtualised by the technology (weighting by standard methods e.g. CPU's, Storage Space, Tier, OS if you chose to), assuming that you have the data to support this. If not, then speak to your ifrastructure teams, they should be able to advise on how you can identify which parts of the CMDB are using HCI technology.
The third option (which is the last resort really) is to simply allocate this cost to your Data Center and spread the cost to all your infrastructure hosted in the Data Center.
I would be interested in hearing from others who are using this technology and have managed to recharge it.
Hope that helps, good luck.