Battery shutting of at 40%

[mkhud_nd]

Hie there I hope you can help. On February 2023 we installed a solar system consisting of a SAKO 5kv inverter, SAKO 48 volt 100ah lithium battery and six 450watt solar panels. Whenever the battery drops to 40% it shuts off and when it charges and it reaches around 60% after being charged from empty it jumps to 100%. Can you help solve this issue?

 

[Rocketman]

Some of the BMS built in counters are not known to be accurate.

You may want to get a Victron Smartshunt (or Bmv712) to accurately measure the current flowing into and out of the battery- $112

Also if your cells have become unbalanced, you could be shutting down due to a low cell voltage?

Can you see the cell balances just before it shuts down? And when it says it just got to 100%?

Good Luck

 

[WrenchLight]

There are a few reasons this can happen. Here are some:
1. The BMS can't keep track of the state of charge because it's using mostly coulomb counting with voltage correction.
2. The cells have become unbalanced. (most likely)
3. One or more cells is reaching end of life (less likely).
Read the voltages from the BMS. Does your solar tracker keep track of min and max cell voltages that you can plot over time?
Is the battery still under warranty?
Some BMS models can't keep the cells balanced. It is possible to manually top-balance the cells if you have a power supply. Bring up the low cells one at a time to the same voltage as the fully charged cell. Don't set the power supply voltage to higher than 3.6V for LiFePO4 cells in case you get distracted from monitoring the voltage.

 

[mkhud_nd]

Some of the BMS built in counters are not known to be accurate.

You may want to get a Victron Smartshunt (or Bmv712) to accurately measure the current flowing into and out of the battery- $112

Also if your cells have become unbalanced, you could be shutting down due to a low cell voltage?

Can you see the cell balances just before it shuts down? And when it says it just got to 100%?

Good Luck

I'll look at them just before it shuts down. What should the cell balances read?

 

[Rocketman]

You are looking for differences - are they all around 3.000v or are the all but one at 3.125v and one is at 2.850v.

Also on charging are they all close to the same 3.500v or all they all at 3.312v but one that is at 3.650v.

You are looking for the high and low and where most cells are at each of those spots. And which cells are the high cells and which are the low cells - is it the same cell?

 

[mkhud_nd]

There are a few reasons this can happen. Here are some:
1. The BMS can't keep track of the state of charge because it's using mostly coulomb counting with voltage correction.
2. The cells have become unbalanced. (most likely)
3. One or more cells is reaching end of life (less likely).
Read the voltages from the BMS. Does your solar tracker keep track of min and max cell voltages that you can plot over time?
Is the battery still under warranty?
Some BMS models can't keep the cells balanced. It is possible to manually top-balance the cells if you have a power supply. Bring up the low cells one at a time to the same voltage as the fully charged cell. Don't set the power supply voltage to higher than 3.6V for LiFePO4 cells in case you get distracted from monitoring the voltage.

How do you balance the cells ?

 

[marionw]

If you purchased the batteries with a communications port you can download the software from https://sakopower.com/download
With this software you can monitor the batteries.
To get the battery BMS to balance cells you will need to charge with 56 volts (16 cells x 3.5 volts per cell). Most BMS will start to balance cells at 3.45 volts (depends on settings in the BMS which the software will allow you to view) and once balancing starts the BMS will reset SOC to 100%

You can use up to 58.4VDC but you would be better to use 56.5 for bulk until you have the software to more closely monitor your system

The instruction for 51.2V 100AH LiFePo4 battery as sample:
1.1 Discharge current do not more than 100A
1.2 Charge current do not more than 50A
1.3 Bulk charging voltage: 58.4VDC
1.4 Low DC cut-off voltage: 48VDC
1.5 Low DC alarm voltage：44.8V

 

[mkhud_nd]

You are looking for differences - are they all around 3.000v or are the all but one at 3.125v and one is at 2.850v.

Also on charging are they all close to the same 3.500v or all they all at 3.312v but one that is at 3.650v.

You are looking for the high and low and where most cells are at each of those spots. And which cells are the high cells and which are the low cells - is it the same cell?

The high is a 3.239 and the low is at 3.140 and it's different cells

 

[mkhud_nd]

If you purchased the batteries with a communications port you can download the software from https://sakopower.com/download
With this software you can monitor the batteries.
To get the battery BMS to balance cells you will need to charge with 56 volts (16 cells x 3.5 volts per cell). Most BMS will start to balance cells at 3.45 volts (depends on settings in the BMS which the software will allow you to view) and once balancing starts the BMS will reset SOC to 100%

You can use up to 58.4VDC but you would be better to use 56.5 for bulk until you have the software to more closely monitor your system

The instruction for 51.2V 100AH LiFePo4 battery as sample:
1.1 Discharge current do not more than 100A
1.2 Charge current do not more than 50A
1.3 Bulk charging voltage: 58.4VDC
1.4 Low DC cut-off voltage: 48VDC
1.5 Low DC alarm voltage：44.8V

I don't the battery has a communications port

 

[mkhud_nd]

If you purchased the batteries with a communications port you can download the software from https://sakopower.com/download
With this software you can monitor the batteries.
To get the battery BMS to balance cells you will need to charge with 56 volts (16 cells x 3.5 volts per cell). Most BMS will start to balance cells at 3.45 volts (depends on settings in the BMS which the software will allow you to view) and once balancing starts the BMS will reset SOC to 100%

You can use up to 58.4VDC but you would be better to use 56.5 for bulk until you have the software to more closely monitor your system

The instruction for 51.2V 100AH LiFePo4 battery as sample:
1.1 Discharge current do not more than 100A
1.2 Charge current do not more than 50A
1.3 Bulk charging voltage: 58.4VDC
1.4 Low DC cut-off voltage: 48VDC
1.5 Low DC alarm voltage：44.

If you purchased the batteries with a communications port you can download the software from https://sakopower.com/download
With this software you can monitor the batteries.
To get the battery BMS to balance cells you will need to charge with 56 volts (16 cells x 3.5 volts per cell). Most BMS will start to balance cells at 3.45 volts (depends on settings in the BMS which the software will allow you to view) and once balancing starts the BMS will reset SOC to 100%

You can use up to 58.4VDC but you would be better to use 56.5 for bulk until you have the software to more closely monitor your system

The instruction for 51.2V 100AH LiFePo4 battery as sample:
1.1 Discharge current do not more than 100A
1.2 Charge current do not more than 50A
1.3 Bulk charging voltage: 58.4VDC
1.4 Low DC cut-off voltage: 48VDC
1.5 Low DC alarm voltage：4

 

[mkhud_nd]

If you purchased the batteries with a communications port you can download the software from https://sakopower.com/download
With this software you can monitor the batteries.
To get the battery BMS to balance cells you will need to charge with 56 volts (16 cells x 3.5 volts per cell). Most BMS will start to balance cells at 3.45 volts (depends on settings in the BMS which the software will allow you to view) and once balancing starts the BMS will reset SOC to 100%

You can use up to 58.4VDC but you would be better to use 56.5 for bulk until you have the software to more closely monitor your system

The instruction for 51.2V 100AH LiFePo4 battery as sample:
1.1 Discharge current do not more than 100A
1.2 Charge current do not more than 50A
1.3 Bulk charging voltage: 58.4VDC
1.4 Low DC cut-off voltage: 48VDC
1.5 Low DC alarm voltage：44.8V

 

[mkhud_nd]

The port is an RJ 45 can I download the software and connect my laptop directly to it

 

[marionw]

You need to find out if the manufacturer has the correct cable to connect the battery to a computer. If not it may be possible to build a cable but you will need the pinout of the RJ 45.

The battery RJ 45 more than likely uses either the RS485 or CAN protocol (or both). You will need an RS485 to USB (or CAN to USB) converter. The manufacturer provided cable would include the converter.

If the manufacturer can't provide a cable and you can get the RJ45 pinout it might be possible to build your own cable