Inverter/Charger Systems

Back in the olden days this system is what you got if you wanted solar. Most applications were for off-grid situations.  In spite of the recent proliferation of hybrid systems and deep cycle lithium battery banks the inverter/charger is still going strong, and for good reasons. Key to their longevity is their versatility, easily adaptable to a wide variety of system designs. 

All modern inverter/chargers are fully compatible with the various types of lead-acid batteries and consequently are low-voltage inverters. The development of lead-acids has not stood still and these remain the backbone of off-grid installations as well as being perfectly suited to on-grid home installations where the high cost of lithiums can be a deterrent to having a solar system at all.  Most modern inverter/chargers are also compatible with low voltage lithium packs. 

The inverter/charger unit itself consists basically of the DC/AC inverter module, a mains voltage charger and a transfer switch. There are two operating modes; an inverter mode where the household loads are fed from the battery and/or solar energy, and a mains mode where the grid (or standby generator) feeds through to the AC output port via the transfer switch. Whilst in mains mode, if the grid fails then the transfer switch changes mode automatically. Many models have auxiliary contacts for switching back to mains mode if a low-voltage battery limit is reached.  There are no MPPT solar charge inputs on the unit and you use one or more discrete component solar charge controller(s) instead.  This arrangement offers greater flexibility in the array configuration than does a hybrid's inbuilt MPPT chargers.  Likewise the battery management system is not integral and is added externally. There is more wiring involved than with a hybrid but the end result can be very rugged and widely adaptable to meet various installation scenarios. 

This system is not the usual go-to option for an on-line household installation but that shouldn't put you off. The inverter/charger can offer greater versatility and is certainly the better choice, if not the only choice,  if you'll be using lead-acid batteries.  There is a wide selection of inverter/charger power outputs available to cater for various configurations and smaller units are useful for basic energy standby systems or where a household c/breaker board has a critical load section partitioned off. This is how we've arranged our system at home (ref My System).