In AC coupled off-grid systems the battery is typically connected to a multi-mode inverter/charger. Nowadays we also get hybrid solar inverters that allow batteries connected to them directly.
In that case the battery is typically charged directly from solar panels without the redundant DC/AC and subsequent AC/DC conversion required when using the multi-mode inverter/charger.
Why would I then ever use the multi-mode inverter/charger to attach batteries?
Selection criteria are more than just efficiency. One must look at other factors such as cost, reliability, parts availability, technical support, and ease of service. Look at the system solution.
Most modern hybrid inverters are not designed for permanent off-grid use and have limited surge power capability and no backup generator controls. Also some manufactures will not honour the warranty if the system is not grid-connected. The Sol-Ark hybrid inverter is one of the few exceptions.
DC-coupled off-grid systems using one or more MPPT solar charge controllers require an inverter-charger and are extremely efficient and flexible. Also if one of the MPPT’s fails, it can easily be taken out and repaired or replaced without shutting down the whole system.