2 Growatt Inverters set in parallel using the same battery. One charging and one discharging the battery at the same time!!

[msidani]

Hello,

I have 2 felicity 8.7 Kwh batteries that are set up in parallel. They act as one big battery.

I also have 2 Growatt 5000es connected in parallel. Both are connected to the big battery. I attached the connection to the battery as an image.

The problem is that at night with no PV, and when there is no load on the system:

First inverter is discharging 100W from the battery
Second inverter is charging the battery with 48W
(I attached the images of both inverters loggers)

How is this possible? Are the inverters charging the battery from itself? Is one inverter charging the other?

It is worth noting that sometimes when inverter 1 reads 90% of the battery, Inverter 2 reads 89%. Electrician told me that might be because one DC cable length difference between the battery and inverter 1 and the battery and inverter 2.

Any help would be greatly appreciated, I’m afraid of the batteries charging themselves decreasing their lives substantially. Thank you.

 

[sunshine_eggo]

This sounds like a calibration issue where the units are measuring different current, and one is way out of whack.

 

[msidani]

This sounds like a calibration issue where the units are measuring different current, and one is way out of whack.

Big Thanks!
Can this damage the battery? And what would be a way to fix this?

 

[sunshine_eggo]

Big Thanks!
Can this damage the battery? And what would be a way to fix this?

Calibrating things fixes calibration issues. I don't think that's a user option on your unit. Furthermore, what you're seeing happen can't actually happen. Current can't flow both directions at the same time. Your battery is either net discharging or net charging. You can verify that with a clamp DC ammeter.

I would contact your equipment supplier for support.

 

[msidani]

Calibrating things fixes calibration issues. I don't think that's a user option on your unit. Furthermore, what you're seeing happen can't actually happen. Current can't flow both directions at the same time. Your battery is either net discharging or net charging. You can verify that with a clamp DC ammeter.

I would contact your equipment supplier for support.

Thanks again for the great help!

Yeah here is Lebanon there is 0 support. Dealers are just business men with 0 knowlege. I had to research everything and build the system myself.

The thing is I don’t mind this wrong reading as long as it doesn’t short the battery or reduce its life. Net charging/discharging relieved me a little.

Do you think the problem my hurt my battery?

Again, thanks a lot!

 

[sunshine_eggo]

Thanks again for the great help!

Yeah here is Lebanon there is 0 support. Dealers are just business men with 0 knowlege. I had to research everything and build the system myself.

The thing is I don’t mind this wrong reading as long as it doesn’t short the battery or reduce its life. Net charging/discharging relieved me a little.

Do you think the problem my hurt my battery?

Batteries are designed to charge and discharge. That's all that's going on.

Get a clamp DC ammeter. Check the current going to one inverter then the other, multiply each value by the battery voltage at the terminals, and that's the power going to/from each battery. You can then compare that to what the inverters report.