Deye inverter 12KW SUN-12K-SG04LP3-EU do not allow batteries to be discharged below 44V.

[Rossen-Javor]

Hello everyone!

Deye inverter 12KW SUN-12K-SG04LP3-EU - 2 units, working in parallel, with an EV Li-Po battery pack of 63.6 kWh, total electric charge: 1320Ah, operating voltage of the batteries according to the BMS in the range from 49.32V to 39.84V, after another firmware update (made by Deye without anyone asking me...on March 07, 2025) the discharge of the batteries was limited to 44V = 54% of the battery capacity. Before the update, the inverters discharged the batteries to 40V.

In addition, the option to enter data about when the batteries are empty in volts has disappeared in the inverter menu - the "Batt empty V" cell is no longer there. This option has also disappeared from the Deye cloud platform and Deye solar me.

I have written several reports to Deye support, to all possible emails, but no one responds...

This situation is absurd, because on the website, regarding the technical characteristics of these inverters, the following is written: "Battery Compatibility: Inverters work effectively with both lead-acid and lithium-ion batteries, accommodating a voltage range of 40-60 V, with a self-adjusting battery management system (BMS)." The same operating range of batteries with which these inverters can work effectively (40-60 V) is also marked on the stickers of the inverters themselves.

For me, the problem arose after the update HMI: Ver 1001-C-04D, MAIN: Ver 2006-1151-1807

I have friends who have other models of Deya inverters and in their menus, as well as in online platforms, the cell "Batt empty V" still exists (I attach a photo).

If you have the same model of inverters as mine, can you share if the above setting options still exist for you?

Has anyone of you encountered this problem and found a solution?

 

[Quattrohead]

after another firmware update (made by Deye without anyone asking me

Terrible

 

[timselectric]

That sucks.
I don't know if there is a fix, afterwards.
I guess you didn't see our warnings about connecting to the internet.

 

[Rossen-Javor]

That sucks.
I don't know if there is a fix, afterwards.
I guess you didn't see our warnings about connecting to the internet.

Please stop with your meaningless comments under every post of mine!

 

[timselectric]

Please stop with your meaningless comments under every post of mine!

Not sure what you are talking about, but no problem, I can put you on ignore.

 

[robby]

Out of curiosity why would you want to discharge the battery below 5% ?
You are already in dangerous territory and the amount of Power at the Knees between 5% and 0% is going to last about an extra 2-5 minutes.
I suspect the reason why Deye added that to the update is because they now sell LFP batteries and they probably wanted to protect their own butt from future warranty issues.

 

[Rossen-Javor]

Not sure what you are talking about, but no problem, I can put you on ignore.

GREAT!

 

[Rossen-Javor]

Out of curiosity why would you want to discharge the battery below 5% ?
You are already in dangerous territory and the amount of Power at the Knees between 5% and 0% is going to last about an extra 2-5 minutes.
I suspect the reason why Deye added that to the update is because they now sell LFP batteries and they probably wanted to protect their own butt from future warranty issues.

If you read carefully what I wrote, you will see that I want to discharge my battery below 54% (fifty-four percent) = 44V.

In addition, my battery parameters are as follows:

Minimum allowable battery discharge up to: 32.4V (2.7V per cell *12)

Maximum allowable battery charge up to: 50.4V (4.2V per cell *12)

Set limit:
According to BMS - Minimum allowable battery discharge - up to 39.84V (3.32V per cell *12)

According to BMS - Maximum allowable battery charge - up to 49.32V (4.11V per cell *12)

Also, if you paid attention to the capacity of the battery pack, this 54% is equal to approximately 34 kWh, which at my average consumption is about 7 hours of consumption.

So, 5% might be equivalent to 3 to 5 minutes of consumption for you, with your batteries and your average consumption. But for me, 5% is equal to more than 3 kWh, which with my average consumption is about 40-60 minutes.

That's why it's crazy that I can't discharge my batteries below 44 Volts = 54%. Moreover, the manufacturer of the inverters himself has indicated in the technical characteristics that they work stably with batteries in the range from 40 to 60 Volts.

 

[Supervstech]

If you read carefully what I wrote, you will see that I want to discharge my battery below 54% (fifty-four percent) = 44V.

In addition, my battery parameters are as follows:

Minimum allowable battery discharge up to: 32.4V (2.7V per cell *12)

Maximum allowable battery charge up to: 50.4V (4.2V per cell *12)

Set limit:
According to BMS - Minimum allowable battery discharge - up to 39.84V (3.32V per cell *12)

According to BMS - Maximum allowable battery charge - up to 49.32V (4.11V per cell *12)

Also, if you paid attention to the capacity of the battery pack, this 54% is equal to approximately 34 kWh, which at my average consumption is about 7 hours of consumption.

So, 5% might be equivalent to 3 to 5 minutes of consumption for you, with your batteries and your average consumption. But for me, 5% is equal to more than 3 kWh, which with my average consumption is about 40-60 minutes.

That's why it's crazy that I can't discharge my batteries below 44 Volts = 54%. Moreover, the manufacturer of the inverters himself has indicated in the technical characteristics that they work stably with batteries in the range from 40 to 60 Volts.

At 44V, a 16S battery would be at 9% and nearly depleted...

What cell configuration do your batteries run?

 

[Supervstech]

Lithium Iron Phosphate cells charge goes from 2.5v/cell to 3.65V/cell...

And below 3V/cell, there is VERY little energy left...

Draining down to zero is not wise, draining below 2.5V is unwise...
2.5V/cell would be around 40V, and, while yes, you can deplete the cells this low, odds are high the BMS would trip out on a cell reaching LCD if you did.
44V s a nice deep discharge, leaving a bit of cushion for the bms.

 

[Supervstech]

I CERTAINLY agree with you that the inverter updates should not do things like this without your knowledge, but that is why i would want total control over update installs...

 

[Rossen-Javor]

At 44V, a 16S battery would be at 9% and nearly depleted...

What cell configuration do your batteries run?

At 44V, a 16S battery would be at 9% and nearly depleted...

What cell configuration do your batteries run?

Lithium Iron Phosphate cells charge goes from 2.5v/cell to 3.65V/cell...

And below 3V/cell, there is VERY little energy left...

Draining down to zero is not wise, draining below 2.5V is unwise...
2.5V/cell would be around 40V, and, while yes, you can deplete the cells this low, odds are high the BMS would trip out on a cell reaching LCD if you did.
44V s a nice deep discharge, leaving a bit of cushion for the bms.

12 EV Li-Po batteries Hyundai Mobis 12s, 110Ah, 48V, 5.3kWh, LG cell, with two modules of 2.65 kWh each;

Minimum allowable battery discharge up to: 32.4V (2.7V per cell *12)
Maximum allowable battery charge up to: 50.4V (4.2V per cell *12)

Set limit:
According to BMS - Minimum allowable battery discharge - up to 39.84V (3.32V per cell *12)
According to BMS - Maximum allowable battery charge - up to 49.32V (4.11V per cell *12)

Of course, in my case at 44V the batteries are not charged to 9%, but to 54-55% (see also the photo).

So, let's be clear - there is no problem with batteries discharging to 40 Volts = 3.33 V per cell.

 

[Supervstech]

12 EV Li-Po batteries Hyundai Mobis 12s, 110Ah, 48V, 5.3kWh, LG cell, with two modules of 2.65 kWh each;

Minimum allowable battery discharge up to: 32.4V (2.7V per cell *12)
Maximum allowable battery charge up to: 50.4V (4.2V per cell *12)

Set limit:
According to BMS - Minimum allowable battery discharge - up to 39.84V (3.32V per cell *12)
According to BMS - Maximum allowable battery charge - up to 49.32V (4.11V per cell *12)

Of course, in my case at 44V the batteries are not charged to 9%, but to 54-55% (see also the photo).

So, let's be clear - there is no problem with batteries discharging to 40 Volts = 3.33 V per cell.

Ahhh.
Gotcha. There certainly is a GOTCHA using non standard batteries with many inverters.
Most are wired to handle from 60V to 40 max range.
Many require communication and compatible brands of batteries.

Did they used to work before the update? I doubt any 48V inverter can be configured to function down to 32V...

 

[Rossen-Javor]

Ahhh.
Gotcha. There certainly is a GOTCHA using non standard batteries with many inverters.
Most are wired to handle from 60V to 40 max range.
Many require communication and compatible brands of batteries.

Did they used to work before the update? I doubt any 48V inverter can be configured to function down to 32V...

As I have already written in detail above, this model of inverters worked without problems with these batteries (6 months), discharging them to 40V, since the inverter settings allowed to enter a "Batt empty" value of up to 40V (according to the BMS, the batteries were limited to a discharge of 49.32V). The problems started after the upgrade. Now the inverters allow a discharge only up to 44V.

I don't see the point in answering the same question several times - at the beginning I wrote the following "Before the update, the inverters discharged the batteries to 40V."
I hope it is now clear what the problem is.

 

[shadowmaker]

I have same exact inverters. I'm using LPF and LFA batts, so never had any reason to go under 46V. Mine are connected to internet all the time so I probably have that same update too. I'll check later today and get back to you.

I do have noticed that apps (Solarman, Deye Cloud) have more limited setting range than actual Deye screen.

 

[Rossen-Javor]

I have same exact inverters. I'm using LPF and LFA batts, so never had any reason to go under 46V. Mine are connected to internet all the time so I probably have that same update too. I'll check later today and get back to you.

I do have noticed that apps (Solarman, Deye Cloud) have more limited setting range than actual Deye screen.

"I do have noticed that apps (Solarman, Deye Cloud) have more limited setting range than actual Deye screen."

I have found the same, but in this case, after the upgrade, the "Battery Empty V" menu is missing both in the apps and in the menu of the inverter itself.

 

[shadowmaker]

Checked it and my inverters have "Low Batt V" and "Shutdown"(voltage) just like manual suggests. I don't think there has been any updates since I requested one almost two years ago.

 

[Rossen-Javor]

Checked it and my inverters have "Low Batt V" and "Shutdown"(voltage) just like manual suggests. I don't think there has been any updates since I requested one almost two years ago.

The question is, do you have the "Batt Empty V" menu?
See attached picture.

 

[shadowmaker]

The question is, do you have the "Batt Empty V" menu?
See attached picture.

No. Both my apps and my inverters are showing only "Shutdown" in battery menu which I can set down to 41V. If I set "Shutdown" to 41V I can also set "Low Batt V" down to 41V. I guess my "Shutdown" equals your "Batt Empty V".

 

[Rossen-Javor]

No. Both my apps and my inverters are showing only "Shutdown" in battery menu which I can set down to 41V. If I set "Shutdown" to 41V I can also set "Low Batt V" down to 41V. I guess my "Shutdown" equals your "Batt Empty V".

What you are telling me are different menus. You are not with "Batt Type" "BMS Lithium Batt". That's why you see "Batt Low V" and "Batt Shutdown V".
My batteries are a different type and I work with the "Batt Type" "BMS Lithium Batt" menu. That's why I also have these menus, but with me these indicators are in percentages, not in volts.
The "Batt Empty V" menu is something completely different. I had it, and now it's gone.