Adding micro inverters to supplement AC load

[cDc1979]

So, all hypothetical of course.

I have a 48v completely off grid system, comprising of a 1000w inverter, 4kw battery and a 150/35 charge controller. Lets say I am pulling 700watts sustained from my inverter. Could I THEORITICALLY plug in a cheap "grid tie" AC inverter from some small solar arrays to supplement the load? I.e. if I add a 300w micro inverter downstream of my DC inverter, then my 700w load becomes 400w on the DC side? (roughly, obviously some minor losses). As long as there is a sustained load on the AC end, there should be no risk of back feed?

Thanks!

 

[cs1234]

So, all hypothetical of course.

I have a 48v completely off grid system, comprising of a 1000w inverter, 4kw battery and a 150/35 charge controller. Lets say I am pulling 700watts sustained from my inverter. Could I THEORITICALLY plug in a cheap "grid tie" AC inverter from some small solar arrays to supplement the load? I.e. if I add a 300w micro inverter downstream of my DC inverter, then my 700w load becomes 400w on the DC side? (roughly, obviously some minor losses). As long as there is a sustained load on the AC end, there should be no risk of back feed?

Thanks!

If your load is "sustained" and never drops off, yes, it should work. The problems arise when it's not "sustained".

EDIT : Pretty much everybody here will tell you not to do it, just putting that out there.

 

[n2aws]

The safe way to do what you are asking is called "AC Coupling" and you'd need an inverter that supports it.

There are several on the market.

For instance, I have a Schnieder XW Pro, and it supports AC coupling. I can use a UL 1741 grid tie microinverter on the "AC Out" side, and it's safe to do. The XW will slowly adjust the grequency from 60hz, to tell the micros to throttle back their output as my batteries approach "full"

 

[SparkyJJO]

If you had a way that when the load is on, the micro is on, and when the load shuts off the micro shuts down.

Some relays would work I would think, have to modify whatever appliance to when operating would close the AC contacts to the micro, allowing it tovstart working, nut as soon as the appliance shuts off it kills connection to the micro (which causes it to do a rapid shutdown).

At least I think this should work.