Growatt in SBU Mode - Grid did not kick in after battery empty

[bt77]

Hi,

We installed at a friend's house the following setup:
- Growatt SPF6000 ES PLUS inverter
- 3.2 kWp PV panels
- 10 kWh LiFePO4 battery back (CAN connection from BMS to Growatt)
- Grid is also connected to grid input terminals

The system had been running just fine for the last 10 days but it was all sunny days so battery was needed after sunset through the night and in the morning the solar would charge it again. Evenings usually started with 100% SOC (or maybe 90% but definitely not less). Today it was quite cloudy so the evening could not start with a high SOC, maybe 70% or so. On top of that my friend had some high power loads on, such as a water heater, iron, oven etc. So the battery drained in 3-4 hours.

Now here is the problem: When battery was empty, he got the Fault 52 (Bus voltage too low) and lost power in the house. The inverter was in SBU mode, which basically means the grid must have kicked in when battery was empty. But it didn't and simply went into Fault 52 mode.

Since SBU mode is defined as below, I would expect the grid to continue supplying power and the battery would start charging again in the morning when PV produced energy again (Charging is set to SOLAR ONLY).

SBU:
Solar energy provides power to the loads as first priority.
If solar energy is not sufficient to power all connected loads, battery will
supply power to the loads at the same time.
Utility provides power to the loads only when battery voltage drops to
either low-level warning voltage or the setting point in program 12.

Any thoughts? Has anyone had this problem before?

 

[JJJALLOFFGRID]

Double check your grid power in with volt meter from I assume a breaker in the house.

 

[wildbillpdx]

If you have it set to Solar only, it may not charge from grid:

 

[bt77]

If you have it set to Solar only, it may not charge from grid:

View attachment 167762

I know. I don't want the battery to charge from grid. I want the grid to supply the loads if the battery is empty (and obviously no solar). So that's SBU.
Battery can charge later when there is solar output again.
But why was there a power outage when battery was empty, instead of switching to the grid as per SBU...

 

[bt77]

Double check your grid power in with volt meter from I assume a breaker in the house.

Yeah, no problem there. Grid power is fine. In fact because of the problem now my friend is temporarily connected to the grid, we disconnected the inverter.

 

[timselectric]

What is setting #12 set at?

 

[bt77]

What is setting #12 set at?

10%. Our intention was to set voltage point back to grid if battery drops to 10%.

Setting 13 at 30%, so setting back to battery when it reaches 30% again (Solar Only charging).

 

[TomC4306]

10%. Our intention was to set voltage point back to grid if battery drops to 10%.

Setting 13 at 30%, so setting back to battery when it reaches 30% again (Solar Only charging).

Argh.
Don't use percentages.
Translate those to a voltage.

To grid- 49v
Back to battery - 52v
SBU, but Solar first charging, not only.

At 49 volts, grid takes over loads + 1½ amps.
This 1½amps acts as buffer current but also nets a charge to the battery. Just enough to not leave the battery at a very low voltage for an extended period of time. In my setup it raises my state of charge from about my 0% to 8 or 9% by the time the sun comes up again.

 

[bt77]

Argh.
Don't use percentages.
Translate those to a voltage.

To grid- 49v
Back to battery - 52v
SBU, but Solar first charging, not only.

At 49 volts, grid takes over loads + 1½ amps.
This 1½amps acts as buffer current but also nets a charge to the battery. Just enough to not leave the battery at a very low voltage for an extended period of time. In my setup it raises my state of charge from about my 0% to 8 or 9% by the time the sun comes up again.

But the settings are in percentages since the BMS and Growatt are connected with CAN communications and Li is selected in Setting 5.

Are you suggesting not to use the BMS communications and select User Defined Battery in Setting 5?

 

[TomC4306]

But the settings are in percentages since the BMS and Growatt are connected with CAN communications and Li is selected in Setting 5.

Are you suggesting not to use the BMS communications and select User Defined Battery in Setting 5?

Yes.
It's awesome ?.
And it works like physics are supposed to work.

 

[bt77]

Yes.
It's awesome ?.
And it works like physics are supposed to work.

OK I will try, thanks!

But is this like a known flaw with Growatt? Percentages and Li mode in Setting 5 not working properly?

 

[timselectric]

Percentage is fine.
10% is pretty low. You aren't saving anything for reserve, if the grid goes down. But, that's just a personal choice.
As long as it sees the grid input. It should switch over. I can't think of another setting that would block the operation.

 

[bt77]

Percentage is fine.
10% is pretty low. You aren't saving anything for reserve, if the grid goes down. But, that's just a personal choice.
As long as it sees the grid input. It should switch over. I can't think of another setting that would block the operation.

OK maybe I will first try higher percentages for 12 and 13, keeping the BMS communications.

If it doesn't work, I will also try @TomC4306 's suggestion and set the voltages for a User Defined Battery.

Let's see. I will post findings here.

 

[timselectric]

I'm not a fan of BMS communications.
But, it shouldn't make any difference for your issue.

 

[wildbillpdx]

I know. I don't want the battery to charge from grid. I want the grid to supply the loads if the battery is empty (and obviously no solar). So that's SBU.
Battery can charge later when there is solar output again.
But why was there a power outage when battery was empty, instead of switching to the grid as per SBU...

It says clearly in the manual grid will NEVER be used to charge the batteries:

 

[timselectric]

It says clearly in the manual grid will NEVER be used to charge the batteries:

View attachment 167820

They don't want grid to charge the batteries.

 

[bt77]

Exactly, we don't.

Grid not charging the battery has nothing to do with my problem. The grid should supply the loads when the battery is empty, but it didn't.

I am now thinking maybe the grid was out (my friend has blackouts every now and then, not uncommon) when the 10% was reached, so it kept draining the battery. When the power was back, it was perhaps too late since the Fault 52 was already there.

 

[timselectric]

I am now thinking maybe the grid was out (my friend has blackouts every now and then, not uncommon) when the 10% was reached, so it kept draining the battery. When the power was back, it was perhaps too late since the Fault 52 was already there.

Very likely the case.

 

[timselectric]

And a good reason for more reserve capacity.

 

[Paulfrench35]

I just had the same problem today, have you changed your settings? Is it better? What exactly does error 52 mean?