Dump Load using 14V Grid Tie

[Tom Rent]

I see that some low end grid tie inverters are rated to begin inverting at 14V. Any reason these can't be used to prevent the a 12V battery bank from overcharging, such as having a series of four 300w (derated to 150w) ones to sevice a 500w mill? These are less than $100 units. I've not seen or read of anyone trying this and it would not require relays.

[Rob Beckers]

Hi Tom,

Can you post a link to these inverters.
Make sure they are UL listed (or cUL/CSA listed if you're in Canada). Without that they won't pass inspection.

By itself your idea is sound: One of my customers used an Aurora inverter to "sell back" excess energy from a large (high voltage) battery bank. The cut-in voltage of the inverter, and its "MPPT curve" were set so it would let the battery bank charge up normally, and pushing power to the grid would only happen when the batteries were full. Last I heard that worked like a charm.

If you need the batteries anyway (for power when the grid is down) then this is great. If you're adding batteries to the mix just to control the turbine it gets to be expensive and takes away 5 - 10% of efficiency (floating batteries takes energy).

-RoB-