Relay or Switch to turn off panels when grid kicks in

ausman

I have a small battery bank but a large solar setup. The inverter is tied with the grid. When grid is available, all the load is shifted to grid and solar charges the battery. When grid is off, solar is used to run the load and to charge the battery.

At night or when solar is not available due to bad wearher, the inverter (with charger builtin) charges the bank using grid.

When the grid is available, i get the current more than the recommended charging rate for the battery bank.

What i want to get is to shut off a string of panels when the load is on grid so that battery bank doesn't get the current more than the recommended charging rate. For this purpose i am looking for a circuit, switch or relay which can turn off the string (DC) when grid AC is on. And when the AC is off, the panels (DC current) is connected again to the charge controller.

It is to inform you that I have separate cables from every string of panels to charge controller.

westbranch

this
What i want to get is to shut off a string of panels when the load is on grid.......rate   
is what your Charge Controller (CC) does...

WaterWheel

I suspect he's got enough panels to charge his small battery bank at over a c/4 rate and during times when the batteries are deeply discharged the charge controller occasionally pushes more amps than the batteries can handle without damage.

ausman, as has been pointed out to me on this site the early morning sun will limit how much energy your controller is pushing into the bank.      By the time the sun is high you're probably already in absorb.

Many charge controllers can be de-rated (control panel) reducing the Bulk charging amperage.

With a large panel set I'd considering disabling your inverter's charger so you don't charge off the grid when a load spikes (like a well pump) and drops the battery voltage for a few seconds tripping your grid powered charger.         That's what I did.        Also, since my inverter's charger can charge my smaller battery bank (395 amp/hr) at 110 amps I programed my inverter charger so when it is enabled (very rarely) it only charges at 28% (about 30 amps).     95% of my charging is off the panels.

With a lot more panels than batteries even on cloudy days you can get a fair amount of charge in the batteries allowing you to get by another night without using the grid to do it.

westbranch

ausman, please list the components of your system by make and model, I read your post as saying you have a hybrid-grid tied system with battery backup...The inverter is tied with the grid.  Thanks for clarifying

romac55

ausman ; sounds like you WANT to be Off-grid , but not quite .  The grid-tie sub-forum is where you want to be asking this , as most of us true off-grid folks don't really know much about the grid charging batteries .