Nice low cost inverters but, will not function correctly with Polyontech lipo batteries as it CANNOT communicate directly with the batteries. You MUST buy the Centurion Solar controller and it is REALLY unreliable. I returned it three times now and it crashed again yesterday with various problems on the software. Think carefully before buying the axpert if you want to upgrade to LiPo batteries. The system is great with up to 100% utilizing through careful control and setup on the CenturionSolar ("piece of Sht") but not stable at all. Sorry Centution solar, you had a good idea but it was poorly developed, not tested and not at all user friendly. The controller requires regular IT maintenance, and your passwords all over the coding makes it impossible.