Can anyone give me an estimate of round trip efficiency of the Multiplus II when used in AC and DC coupled on-grid ESS configurations? I am considering the 48/5000/70-50. Referring to the whitepaper on the 3000 VA unit it appears one way would be ~92-94% at peak output.
It would be helpful to have some data in order to consider the implications of using the existing AC grid tied inverter vs. DC Smart Chargers.
Cheers
Richard
A lot depends on the AC loads and DC loads being pulled. In most cases the AC loads are supplied directly by the Grid tie units during the day and thus they go straight to the loads and this then depends on the dc to AC grid tie inverters efficiency. And or if you then have LARGE DC loads being taken off the batteries as well as the inverter - so its not a cut and dried answer.
Myself I would suspect the AC connect (Grid Tie) would be better as more than likley you wont have any other loads off the battery except the inverters.
And then there is the question of am I exporting to the grid etc etc
If you already have a Grid-Tie the efficiency loss will most likely not be worth the cost of DC MPPTs. If the grid-tie is capable of being on the output of the inverter, I would just leave it and then install any new panels on a DC MPPT.
you also need to take into account battery efficiency (95% for Li, 60% for Pb) AND the standby current for the inverter. However, if you have existing grid tie solar, then it will be cheaper to use that.
