Efficiency of chargers in inverter/chargers

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stephendv
stephendv Solar Expert Posts: 1,571 ✭✭
I was reconsidering the AC coupling approach and key to this is how efficient the inverter/chargers are at charging from the AC side. While some of the manufacturers put the inverter efficiency in their data sheets- I don't see anything about charging. Is this likely to be match the inverter efficiency- or will it be worse?

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,479 admin
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    Re: Efficiency of chargers in inverter/chargers

    I would suspect that charging through the inverter by "back driving" the AC power (connecting a Grid Tied inverter to the AC output of an Off Grid inverter) would be just about as efficient as the inverter itself (and the operating losses too--i.e., 6-30 watts just because the inverter is turned on).

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • 65DegN
    65DegN Solar Expert Posts: 109 ✭✭
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    Re: Efficiency of chargers in inverter/chargers

    I would think that the Sunny Island isn't the only area of possible inneffeciency. There is also the inverting of the solar or wind power to AC before connecting it to the minigrid.
    With a wind turbine it would first be wild AC out of the turbine, rectified to DC, then 60HZ AC out of the grid tie inverter to the minigrid, then back to DC again out of the SMA Sunny Island to charge the batteries.
  • SolaRevolution
    SolaRevolution Solar Expert Posts: 410 ✭✭
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    Re: Efficiency of chargers in inverter/chargers

    According to the equipment specs, the batteries will receive more charging amps from a DC coupled MPPT charge controller than from an AC coupled system.

    Delivering power to AC loads while the sun is shining will be more efficient with an AC coupled system.

    For off-grid:
    Attachment not found.
  • stephendv
    stephendv Solar Expert Posts: 1,571 ✭✭
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    Re: Efficiency of chargers in inverter/chargers

    Thanks all. I've seen similar efficiencies reported in SMA's literature- just wasn't 100% sure that the charging mode would have the same efficiency as the inverter.
    Solarevolution, that diagram explains it really well!