Runaway Voltage ~ Growatt SC48120-MPV SCC

[MrM1]

Bulk / Absorb set to 55v , but the Growatt SCC would reach that and just keep going up. According to the Victron Smart Shunt there is no current, but voltage got up to 58.9 and the BMS (Heltec 200amp 16s x2 ~ 16s2p) shut both batteries banks down. But I do not understand why the SCC voltage never switches to float. Just goes up until the BMS hits Over Voltage Protection. I have also tried lowering the Bulk / Absorb to 53.3 ... same thing. Does not switch over, just keeps going up.

A little system history:
- For Testing: Single string of 360w solar panels x4 in series. DC volts into CC is 140-175vdc (actual). About 1050 watts
- Final array will be 32 360w panels in x8 strings, 4 panels in series each string
- Testing both This SCC and the Growatt 12kw one at at time (not at the same time)
- Growatt SPF 12000T DVM-MPV 250vdc (this is powered off because it is working fine and not needed for testing the SCC)
- Charging from a Growatt SC48120-MPV (250vdc)
- Battery Bank: 48v 16S 280ah x 2 battery banks. Total 560Ah
- BMS: x2 Heltec 16s 200amp with 2 amp active balance
- SOC is about 98% at the start or 3.39v dc per cell

Issue: Had bulk cut off in the Growatt SC48120-MPV SCC set to 55v. Checked in on the system one sunny day and the voltage was at 58.9vdc and climbing (until the BMS shut off charging to both banks due to over voltage protection set to 3.64 v / cell)

So as suggested by Watts247, I lowered the bulk / absorb setting to 53.3 and float to 53. Growatt AIO 12k Inverter and built in SCC is off. Just testing with the Growatt SCC

SCC Settings:
- Charge Amps: 100a (battery bank is 560ah)
- Bat Type: USE
- Bulk: 53.3
- Float: 53
- Low DC Cut off: 42.0
- EQ: DIS

Lowered Bulk Voltage ~ Run Away Voltage Still an Issue:
- After changing to 53.3, the Charge Voltage went from 53 (battery volts), to 55.2 and then up to 56.1 and climbing. (day was not perfect. Weather was on and off clouds)
- No current is flowing according to a Victron Smart shunt at 56.1v dc
- Green light on the SCC is NOT flashing. It is Solid Green (it flashes when charging and current is flowing)
- But the SCC did not switch over to float voltage when bulk voltage was met at 53.3vdc
- Conditions were not perfect, but every indication is the charger voltage would have continued to climb until BMS activated Over Voltage Disconnect Protection again.

Ideas?
Thanks Mike

 

[Checkthisout]

Bulk / Absorb set to 55v , but the Growatt SCC would reach that and just keep going up. According to the Victron Smart Shunt there is no current, but voltage got up to 58.9 and the BMS (Heltec 200amp 16s x2 ~ 16s2p) shut both batteries banks down. But I do not understand why the SCC voltage never switches to float. Just goes up until the BMS hits Over Voltage Protection. I have also tried lowering the Bulk / Absorb to 53.3 ... same thing. Does not switch over, just keeps going up.

A little system history:
- For Testing: Single string of 360w solar panels x4 in series. DC volts into CC is 140-175vdc (actual). About 1050 watts
- Final array will be 32 360w panels in x8 strings, 4 panels in series each string
- Testing both This SCC and the Growatt 12kw one at at time (not at the same time)
- Growatt SPF 12000T DVM-MPV 250vdc (this is powered off because it is working fine and not needed for testing the SCC)
- Charging from a Growatt SC48120-MPV (250vdc)
- Battery Bank: 48v 16S 280ah x 2 battery banks. Total 560Ah
- BMS: x2 Heltec 16s 200amp with 2 amp active balance
- SOC is about 98% at the start or 3.39v dc per cell

Issue: Had bulk cut off in the Growatt SC48120-MPV SCC set to 55v. Checked in on the system one sunny day and the voltage was at 58.9vdc and climbing (until the BMS shut off charging to both banks due to over voltage protection set to 3.64 v / cell)

So as suggested by Watts247, I lowered the bulk / absorb setting to 53.3 and float to 53. Growatt AIO 12k Inverter and built in SCC is off. Just testing with the Growatt SCC

SCC Settings:
- Charge Amps: 100a (battery bank is 560ah)
- Bat Type: USE
- Bulk: 53.3
- Float: 53
- Low DC Cut off: 42.0
- EQ: DIS

Lowered Bulk Voltage ~ Run Away Voltage Still an Issue:
- After changing to 53.3, the Charge Voltage went from 53 (battery volts), to 55.2 and then up to 56.1 and climbing. (day was not perfect. Weather was on and off clouds)
- No current is flowing according to a Victron Smart shunt at 56.1v dc
- Green light on the SCC is NOT flashing. It is Solid Green (it flashes when charging and current is flowing)
- But the SCC did not switch over to float voltage when bulk voltage was met at 53.3vdc
- Conditions were not perfect, but every indication is the charger voltage would have continued to climb until BMS activated Over Voltage Disconnect Protection again.

Ideas?
Thanks Mike

No idea how the growatts work but.

Is there a battery type setting and do you have it to set to lithium?

Can you adjust boost time?

If it's still in flooded mode, what does it think the battery temperature is?

Etc.

 

[sunshine_eggo]

Sounds defective.

 

[MrM1]

No idea how the growatts work but.

Is there a battery type setting and do you have it to set to lithium?

Can you adjust boost time?

If it's still in flooded mode, what does it think the battery temperature is?

Etc.

To my understanding, the Lithium setting in Growatt only works if there is communication connected

I am set to USER, which allows total manual control.

There is no time or cut off current like in Midnite Solar Chargers.

 

[MrM1]

Sounds defective.

Starting to think so

 

[Checkthisout]

To my understanding, the Lithium setting in Growatt only works if there is communication connected

I am set to USER, which allows total manual control.

There is no time or cut off current like in Midnite Solar Chargers.

Does it have a temperature sensor for the battery?

I assume it's just upping the voltage as a result of temperature compensation and thinks it's charging a flooded battery.

Again, not sure exactly how growatt operates.

 

[MrM1]

I have calibrated both this SCC and the Growatt 12kw to the voltage of the Victron Smart Shunt using the calibration tool from Watts247. So every thing is on the same page.

But for testing, I have the 12kw Growatt AIO off because it's built in scc is working fine and executing bulk to float transition as expected.

 

[MrM1]

Does it have a temperature sensor for the battery?

I assume it's just upping the voltage as a result of temperature compensation and thinks it's charging a flooded battery.

Again, not sure exactly how growatt operates.

Not that I know of, at least it wasn't included. But I get your direction.

 

[Checkthisout]

Not that I know of, at least it wasn't included. But I get your direction.

Does this apply to you? Why aren't you using the lithium setting or what settings are you using?

Did you see the note about them needing to match?

 

[Checkthisout]

In other words, I think you are using "USE-02" instead of "LI".

You need to use "LI" and then set 05 and 06 to the same voltage if it doesn't do it automatically.

 

[MrM1]

The newer firmware has a USE and a USE2 setting. I've tried both. But I will try the LI today and see. Thx

 

[Quattrohead]

The newer firmware has a USE and a USE2 setting. I've tried both. But I will try the LI today and see. Thx

It should error on Li with no comms setup.
I have noticed Growatt calibrations to be not too good sometimes, but you say you have calibrated it so I conclude it is faulty.
Try setting the output voltage 5 volts lower and see if it actually tries to regulate.

 

[Checkthisout]

The newer firmware has a USE and a USE2 setting. I've tried both. But I will try the LI today and see.

A different manual but it also instructs you to program the bulk and Float voltage the same when using lithium.

As others have said, the lithium setting apparently is used to communicate with the bms so it won't work.

You are setting two different voltages which both manuals tell you not to do when using lithium.

 

[MrM1]

Will do. Trying now. But very cloudy so won't be know affects for a few days. (battery at 90%)

 

[MrM1]

Well not enough sun (as in none) today to know if setting up Float and bulk to same helped. And too many holidays to know b 4 Friday

 

[Checkthisout]

Well not enough sun (as in none) today to know if setting up Float and bulk to same helped. And too many holidays to know b 4 Friday

Right and to be clear, not saying your cc isn't pushing up daisies but they do make note in both those manuals that float and bulk should be the same when using lithium.

I have a theory as to why but it's probably wrong.

 

[sunshine_eggo]

This is not "Lithium" in the context of the manual.

FWIW, many have reported erratic behavior when setting MPP Solar/Growatt AiO MPPT chargers absorp/float to the same voltage.

Recommend bulk/absorption to 3.45-3.60V/cell and float to 3.375V/cell.

 

[Checkthisout]

This is not "Lithium" in the context of the manual.

FWIW, many have reported erratic behavior when setting MPP Solar/Growatt AiO MPPT chargers absorp/float to the same voltage.

Recommend bulk/absorption to 3.45-3.60V/cell and float to 3.375V/cell.

Curious.

How does the growatt know when to go into float when using lithium?

 

[sunshine_eggo]

Curious.

How does the growatt know when to go into float when using lithium?

The batteries tell it what to do. When set to Lithium, compatible Lithium batteries with communication are required.

Otherwise, with USE type, a float voltage is required to instruct the MPPT to continue to power loads based on battery voltage.

 

[Checkthisout]

The batteries tell it what to do. When set to Lithium, compatible Lithium batteries with communication are required.

Otherwise, with USE type, a float voltage is required to instruct the MPPT to continue to power loads based on battery voltage.

Why does the manual instruct that float and bulk be set to the same voltage when using lithium batteries on the "user" (user input numbers and user supplied lithium batteries without compatible bms)?

If the voltages are set differently, then what strategy does growatt use to transfer to float? Time spent at boost voltage? The amps decay in amps flowing into the battery once boost voltage is reached?