The battery voltage data is used to compensate for voltage drops over the battery cables. This ensures that the battery is charged with the exact voltage configured in the charger - instead of a lower voltage due to resistance in the wiring.
The battery temperature data is used to adjust the charge voltages. When cold, a lead/acid battery typically needs a higher charge voltage…and a lower charge voltage when it's hot.
For lithium batteries, the charge voltages remain the same at all temperatures as long as it’s not too cold. It's better not to charge lithium batteries below 5°C to prevent them from being damaged and degraded.
The battery current data allows the tail current setting (see the MPPT and Orion XS manual for more details) to be used more precisely as, by having the actual battery current, the chargers can decide better if the absorption phase should stop and go to equalisation/float phase.
In VictronConnect, the usage of the battery current data is only shown when these chargers are actually charging. When synchronised charging is enabled, the solar charger also needs to be the master.
When the MPPT or Orion XS is connected to a GX device that sends the battery current, the value from the GX device is used, so the battery current will not show up in the VE.Smart Networking menu (see also chapter 5: Limitations).