battery based inverter charger grid connection

Re: battery based inverter charger grid connection

rama wrote: »

Hi,
I have a battery based 48v inverter charger that I wish to connect to AC mains panel to provide power to household loads (and charging batteries when necessary). If I were to wire the output directly to my AC mains panel would this create backflow into grid (and possibly feeding to other homes?), or is there some sort of inherent protection so I don't have to worry about this?

thanks for any input in advance!

Don't do anything until you understand the requirements. It is unsafe to improperly connect an energy source (generator or AC Inverter) to the "Utility Grid" and in some countries could get you criminally charged.

Ok--Now that is out of the way. Unless the Inverter/Charger is specifically designed for Grid Tie and Off Grid operation (there are some that are)--What will happen is the same thing as if you attached your AC gasoline/diesel generator directly to the grid. Lots of smoke, popped breakers/fuses, and possibly fire in your wiring and generator/inverter.

The normal method to connect an inverter to the grid is to use an AC Transfer Switch. Basically, your Grid would be tied to one input to the transfer switch, the inverter tied to the second input. And the output of the transfer switch would be connected to your "protected loads". When the grid is up, the loads are powered by the grid. When the grid has failed, the switch will connect to your inverter's AC output and power your loads.

Note that some AC inverters (and probably most/all Inverter+Charger units) have internal AC Transfer Switches already. You just connect the "grid" to the AC IN. The DC power to your battery bank. And the AC OUT to your protected loads (never connect the AC OUT of a standard off grid capable inverter to the grid directly). Pretty much just a larger/stand-alone version of a computer UPS (uninterruptable power supply).

So--the first thing to understand is exactly what Brand/Model of AC Inverter (or inverter+charger) you have and to study the installation manual.

Modern AC Inverter+Chargers do not have the capability to back feed the grid... But, interestingly enough, older Inverter+Chargers (at least in the US) could back feed the grid (I guess by charging the battery bank from solar or other power source could push power back through the charge controller).

-Bill