Retrofitting batteries to an existing grid tied system.

[Low Down Dog]

Hi!
Has anyone added a battery bank to a grid tied system consisting of only a PV array and an inverter?
I have a GoodWe GW700-XS inverter.

What equipment would I need?

Thank you very much!

 

[Ampster]

You would need a hybrid inverter. You could leverage your GT system by AC coupling the hybrid inverter to it. If your GT inverter is UL 1741 compliant any UL 1741 hybrid with AC coupling capability should work.

 

[SparkyJJO]

If you have a single inverter, I'd probably just replace with a hybrid inverter and connect the batteries to it. Lots of options for that from many manufacturers.

If it is a bunch of microinverters (like I have) that are UL 1741 compliant, then AC coupling with an appropriate hybrid inverter designed for such would be the way to go (I'm working on doing that with an Outback Radian). Fewer options for this, but it can be done.

 

[Low Down Dog]

You would need a hybrid inverter. You could leverage your GT system by AC coupling the hybrid inverter to it. If your GT inverter is UL 1741 compliant any UL 1741 hybrid with AC coupling capability should work.

Thank you so much!
I'm replying only now, because I've been studying the topic.
As a stop-gap measure, do you think then, that there is no chance of plugging in the battery directly on the PV input sockets on my inverter?

 

[Low Down Dog]

If you have a single inverter, I'd probably just replace with a hybrid inverter and connect the batteries to it. Lots of options for that from many manufacturers.

If it is a bunch of microinverters (like I have) that are UL 1741 compliant, then AC coupling with an appropriate hybrid inverter designed for such would be the way to go (I'm working on doing that with an Outback Radian). Fewer options for this, but it can be done.

Thank you so much!
I'm replying only now, because I've been studying the topic.
As a stop-gap measure, do you think then, that there is no chance of plugging in the battery directly on the PV input sockets on my inverter?
I do not want to sell my current inverter, because I suspect I would no get to much money out of it.

 

[Don B. Cilly]

there is no chance of plugging in the battery directly on the PV input sockets on my inverter?

From what I see, there certainly is.
It's an All-In-One, and it has an MPPT solar charge controller. Just stay within specified limits of voltage and current, and plug away :·)

[EDIT] Actually, I looked at it again, and it's not an AIO, is it? I'm not quite sure what it is, but it looks like it's not meant to have a battery.
So you probably could use one - it would have to be at least 48V, but its not what the unit is meant to do.
Probably best to get a proper AIO and use it... properly :·)
-

 

[400bird]

How would you charge this battery?
The MPPT works one way, discharge.

Another thing most MPPT/PV inverters do is find the maximum power they can pull from the batteries and run at 100% for as long as they can. Remember, MPPT is designed to harvest solar, which isn't always available.
When you hook up the battery isn't going to run them flat at whatever maximum discharge the MPPT can manage.

Some inverters use current sensors to zero export, that would be an exception and work differently.

 

[timselectric]

This wouldn't provide battery backup, either.
Because the inverter is still going to shut down, when the grid does.

 

[400bird]

So, it seems like you're best bet, depending on your goals (which you haven't stated, please tell us) is to either replace your current inverter with an AIO (hybrid) or inverter/charger.

I suppose you might be able to add an AIO.

Are you looking for back up power or time/energy shift.

 

[Ampster]

As a stop-gap measure, do you think then, that there is no chance of plugging in the battery directly on the PV input sockets on my inverter?

There have been discussions about people trying that and the results were mixed. One poster released the smoke from trying that. Remember the inverter is designed to take all the current that a panel can send and that limit is determined by the panel specs so there is a limit for every panel even when directly short circuited. Batteries can put out a lot of current when short circuited so that is the risk. If you have a spare inverter that you don't mind sacrificing for the good of the forum, give it a try and report back. My guess is the odds are not good that it will do anything but blow up solar input circuitry unless you have some way of limiting the current that the battery will put out. That current limit concept was already mentioned earlier.

 

[SparkyJJO]

I would not try it, personally. Unless I didn't mind frying something.