Good afternoon, I have that someone will be able to assist me. I have a fairly new system that I installed to try and fight loadshedding a bit. It consists of a 5kva Must 48v inverter and a Svolt 5.09kwh 48v lithium battery. It is a 15cell battery rated for a max bulk charge of 54.75V

The system is not fully integrated into the flat at the moment. It is only running one portion of the flat (including TV, PC, Router, few bedside lights).

The system is wired to a plug where it gets charged from and the devices runs from a cable with a multiplug. All with fuses in between etc.  At most it draws 400watts. I know it is not ideal, but I am planning on moving and will do a proper installation at the new place.

The issue that I have is that the battery does not seem to charge all the way up. After each loadshedding session, it hold a little bit less of its capacity.  It is currently sitting around 68%.  While the power is on, I can see it charging, I can see the voltages picking up and the amps increase to 12 amps or around that for about 30seconds. Then it drops down and the battery state goes from a CHG state to DSG state? I take it this is from charging to discharging. I can see the input amps dropping from a positive to a -1.7A as an example. That would stop. The battery will go into charging again and the cycle continues.

Why would it discarge and not charge until the battery is full? Is there some setting what could be wrong? Surely it is not because of the way it is charging from the wall socket? 

I have played around with the settings on the inverter within the allowed range specified by the battery manufacturer, but I can’t seem to find the issue.

The photos are taking within minutes of each other.

King regards

1 hour ago, Hein555 said:

Good afternoon, I have that someone will be able to assist me. I have a fairly new system that I installed to try and fight loadshedding a bit. It consists of a 5kva Must 48v inverter and a Svolt 5.09kwh 48v lithium battery. It is a 15cell battery rated for a max bulk charge of 54.75V

The system is not fully integrated into the flat at the moment. It is only running one portion of the flat (including TV, PC, Router, few bedside lights).

The system is wired to a plug where it gets charged from and the devices runs from a cable with a multiplug. All with fuses in between etc.  At most it draws 400watts. I know it is not ideal, but I am planning on moving and will do a proper installation at the new place.

The issue that I have is that the battery does not seem to charge all the way up. After each loadshedding session, it hold a little bit less of its capacity.  It is currently sitting around 68%.  While the power is on, I can see it charging, I can see the voltages picking up and the amps increase to 12 amps or around that for about 30seconds. Then it drops down and the battery state goes from a CHG state to DSG state? I take it this is from charging to discharging. I can see the input amps dropping from a positive to a -1.7A as an example. That would stop. The battery will go into charging again and the cycle continues.

Why would it discarge and not charge until the battery is full? Is there some setting what could be wrong? Surely it is not because of the way it is charging from the wall socket? 

I have played around with the settings on the inverter within the allowed range specified by the battery manufacturer, but I can’t seem to find the issue.

The photos are taking within minutes of each other.

King regards

Perhaps supply the make and model of the BMS so members knowing the BMS can help. 

Also supply your inverter settings like bulk, float, cut out and if you are using USER settings for the battery type. 

54.35 is very close to maximum. Only 40mV from maximum. One cell probably triggers the Over Voltage Protection voltage of 3.65 at that point. And then it shuts down the charging circuit until the inverter draws more current.  If it is a PACE BMS, which I suspect it is, the battery probably never reaches the SOC setting and tail current setting to reset to 100% SOC, and therefore you are seeing drift over time.

Either that, or you might have one cell that is totally out of balance with the rest.

You will only know until you connect a PC to the battery with PBMS Tools, or similar software, to see individual cell voltages and the BMS parameters that are set.

 

It is not necessary to charge up to 3.65V per cell. If you charge up to 3.45V per cell you lose very little of capacity, and it will be better for your cells in the long run.

 

12 hours ago, gimme_power said:

54.35 is very close to maximum. Only 40mV from maximum. One cell probably triggers the Over Voltage Protection voltage of 3.65 at that point. And then it shuts down the charging circuit until the inverter draws more current.  If it is a PACE BMS, which I suspect it is, the battery probably never reaches the SOC setting and tail current setting to reset to 100% SOC, and therefore you are seeing drift over time.

Either that, or you might have one cell that is totally out of balance with the rest.

You will only know until you connect a PC to the battery with PBMS Tools, or similar software, to see individual cell voltages and the BMS parameters that are set.

 

It is not necessary to charge up to 3.65V per cell. If you charge up to 3.45V per cell you lose very little of capacity, and it will be better for your cells in the long run.

 

Thank you for this. It makes sense as I can see the OV status on the battery changing from N to Y. So I guess it is triggering the over voltage on one of the cells and then it stops charging. I can see on the battery that most of the cells are pretty much equally charged. None of them are really that far off from the rest.

The SOC setting is currently set to 95%, but yeah that never gets reached. So basically the voltage on each cell does not need to be 3.65V for the SOC to reach that 95% number if I understand correctly?  So instead of setting the battery up to charge up to 54.7V, you recommend dropping that to 51.75, maybe rounded up to 52V or something?

What should my settings be then on the inverter as I set this up to a previous recommendation when I purchased it? Can you perhaps assist me with this if possible please?

Attached is the settings available on the inverter. I tried to default it and set it to Li setting, but that does not really seem to change either.  So everything is basically on default, what parameters should I look at changing?

Will it recharge on the next cycle or will it be over time? Is there anything else that I have to do?

Thank you very much for the assistance with this as it is giving me gray hair atm and I am bold🙈

Kind regards
 

 

 

1 hour ago, Hein555 said:

Attached is the settings available on the inverter. I tried to default it and set it to Li setting, but that does not really seem to change either.  So everything is basically on default, what parameters should I look at changing?

Hi Hein555,

as you use the inverter as an UPS only I suggest the following settings:

01: UtI, 02: 20A, 05: USE, 06: LtE, 07: ttE, 11: 20A, 16: CUt, 26: 54V, 27: 52V, 29: 1.5 to 2V higher than the BMS cutout voltage. All other settings left at default. Equalizing disabled.

Be aware that in my experience the BMS SOC display is not very reliable. A 15 cell LiFePh pack is full when it reaches and maintains floating voltage 52V. Use a multimeter to confirm battery voltage.

On 2023/07/29 at 12:24 PM, Beat said:

Hi Hein555,

as you use the inverter as an UPS only I suggest the following settings:

01: UtI, 02: 20A, 05: USE, 06: LtE, 07: ttE, 11: 20A, 16: CUt, 26: 54V, 27: 52V, 29: 1.5 to 2V higher than the BMS cutout voltage. All other settings left at default. Equalizing disabled.

Be aware that in my experience the BMS SOC display is not very reliable. A 15 cell LiFePh pack is full when it reaches and maintains floating voltage 52V. Use a multimeter to confirm battery voltage.

Hi Beat, thank you for the reply. I do however see that the numbers you refer to does not match to the numbers on the settings pages? 

11 hours ago, Hein555 said:

I do however see that the numbers you refer to does not match to the numbers on the settings pages? 

I do admit that I referred to the instruction manual of the MKS 5K. Yours might be slightly different. Do you need further details?

@Hein555

In the reply from @Beat your no 5 is 14.

His 16 will be 10 and use SNU. 

26 27 will be 17 and 18.

29 is 19 for your inverter.