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BSL 5.1 Kwh Lithium battery: BMS changes Discharge current limit


Daniemj
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Hi.

We have installed a 8.8KW Sunsynk Hybrid inverter with a 5.1 Kwh BSL lithium battery. The system was running perfectly but it has developed an interesting problem. For the second time now during load shedding at night (battery only source of power), the BMS of the battery changes the Discharge current limit from 105A to 30A. Then, as soon as the load goes over 30A the inverter drops the load in order to "protect" the battery.

Once the whole system is shut down and the battery is reset, it displays the correct value of 105A. Thereafter the system operates normally again (for a day or two until next night time load shedding) 

Any suggestions as to what could cause the battery to change the Discharge current limit (during load shedding)?

BSL.jpg

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I would check out the BMS as the inverter is simply followings the instructions it receives from the BMS. 

I have pylontechs and the discharge limit only drops if my SOC is below 15%. 

Interim solution would be to not use the coms cable and use the manual battery charge and discharge voltage settings. 

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The BMS is there to protect the battery cells. It's likely trying to tell you something, like your cells are out of balance.

If the battery is new, it probably hasn't had enough time to balance the cells as yet. Though such a reduction at 89% SOC sounds like it could be more than just balance.

Make sure that the battery spends good time near the balance voltage. If it doesn't improve, you may have a faulty cell or two. If possible, get the program that shows each cell voltage, and look for one or two outliers. You may need to prepare for a battle convincing your supplier that there is a problem. 

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9 hours ago, Coulomb said:

The BMS is there to protect the battery cells. It's likely trying to tell you something, like your cells are out of balance.

If the battery is new, it probably hasn't had enough time to balance the cells as yet. Though such a reduction at 89% SOC sounds like it could be more than just balance.

Make sure that the battery spends good time near the balance voltage. If it doesn't improve, you may have a faulty cell or two. If possible, get the program that shows each cell voltage, and look for one or two outliers. You may need to prepare for a battle convincing your supplier that there is a problem. 

I hope it has to do with the balance of the cells and not a faulty cell. The battery is new and it normally stays full unless it is discharged during load shedding at night. I will change the program so that the battery is discharged each night and charged the next morning. It could be that one or two cells are way out of balance and then triggers the low voltage warning which then reduce the discharge amps. I must mention that so far after a reset, the battery did perform normal even with a load put onto it.

You mentioned a program that shows each cell voltage. Where can I get such a program? Currently I am using the Solarman APP.

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12 hours ago, Achmat said:

I would check out the BMS as the inverter is simply followings the instructions it receives from the BMS. 

I have pylontechs and the discharge limit only drops if my SOC is below 15%. 

Interim solution would be to not use the coms cable and use the manual battery charge and discharge voltage settings. 

I agree that it has to do with the battery and its BMS. I will see how things develop before using the manual settings instead of the BMS. But thanks for that info. If I have to I will use it, since the installation I am talking about is for my monther in law who stays next to me. She is living there by herself and it is not ideal to have the power go off when it is most needed.

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2 hours ago, Daniemj said:

You mentioned a program that shows each cell voltage. Where can I get such a program?

Oops, I assumed you are running Pylontechs, sorry. I think Pylontech supplies this program on request. You might be able to download an equivalent program from your supplier's web site, or ask them to send it to you (or email you a link).

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On 2021/02/06 at 10:41 PM, Daniemj said:

Hi.

We have installed a 8.8KW Sunsynk Hybrid inverter with a 5.1 Kwh BSL lithium battery. The system was running perfectly but it has developed an interesting problem. For the second time now during load shedding at night (battery only source of power), the BMS of the battery changes the Discharge current limit from 105A to 30A. Then, as soon as the load goes over 30A the inverter drops the load in order to "protect" the battery.

Once the whole system is shut down and the battery is reset, it displays the correct value of 105A. Thereafter the system operates normally again (for a day or two until next night time load shedding) 

Any suggestions as to what could cause the battery to change the Discharge current limit (during load shedding)?

BSL.jpg

Hi Daniemj

This is interesting and not something I have seen before while working on the BSL's. Have you contacted your supplier regarding this problem?

What are your settings on the battery? Please could you provide me all the screens on the battery setup menus? I work mostly with BSL and Sunsynk, I would just like to check a few settings out first. Next step if there aren't any issues there, is to contact your supplier for support and see what they are able to do for you regarding checking the BMS on the battery.

I can do the backup support on the battery if your supplier is unable to help you, please just let me know.

 

Regards

 

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Hi. I have contacted my installer. He has seen this before on an installation with 5 BSL batteries. At some stage those batteries have discharged to 0% and shutdown. After they have been stated up and charged again the problem was gone.

After checking all possible settings we decided to discharge this battery also until it shuts down. We did that, reset the battery and started it up again. 

The battery is much better now but not up to spec yet. Before the BMS would limit the max discharge current form 105A to 30A anytime it discharge at a rate in excess of 50A.

Now the BMS will limit the discharge to 30A as soon as it discharge at a rate  in excess of about 75A (3800Watt). If it is according to spec it should be able to discharge at least up to 100A (with a max of 105A)

Batt discharge.jpg

Battery 1.jpg

Battery 2.jpg

Battery 3.jpg

Battery specs.jpg

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22 hours ago, Daniemj said:

Hi. I have contacted my installer. He has seen this before on an installation with 5 BSL batteries. At some stage those batteries have discharged to 0% and shutdown. After they have been stated up and charged again the problem was gone.

After checking all possible settings we decided to discharge this battery also until it shuts down. We did that, reset the battery and started it up again. 

The battery is much better now but not up to spec yet. Before the BMS would limit the max discharge current form 105A to 30A anytime it discharge at a rate in excess of 50A.

Now the BMS will limit the discharge to 30A as soon as it discharge at a rate  in excess of about 75A (3800Watt). If it is according to spec it should be able to discharge at least up to 100A (with a max of 105A)

Batt discharge.jpg

Battery 1.jpg

Battery 2.jpg

Battery 3.jpg

Battery specs.jpg

Hi Daniemj

Thanks for these and I can suggest a few changes on the settings. If a reset on the battery didn't solve the problem completely, a second reset might work. Otherwise we can get the battery back in for a firmware reset.

Would you please get your installer to contact me via email at [email protected] and I will discuss some aspects with him for your installation and any further installations he does in future.

 

regards

Charles

BackBone Energy

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5 hours ago, Backbone Energy said:

Hi Daniemj

Thanks for these and I can suggest a few changes on the settings. If a reset on the battery didn't solve the problem completely, a second reset might work. Otherwise we can get the battery back in for a firmware reset.

Would you please get your installer to contact me via email at [email protected] and I will discuss some aspects with him for your installation and any further installations he does in future.

 

regards

Charles

BackBone Energy

Hi Charles,

Thank you for the info.

I have forwarded your details to my installer. I am sure he will contact you.

Regards

Danie

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  • 5 months later...
On 2021/02/15 at 10:43 AM, Backbone Energy said:

Hi Daniemj

Thanks for these and I can suggest a few changes on the settings. If a reset on the battery didn't solve the problem completely, a second reset might work. Otherwise we can get the battery back in for a firmware reset.

Would you please get your installer to contact me via email at [email protected] and I will discuss some aspects with him for your installation and any further installations he does in future.

 

regards

Charles

BackBone Energy

Hi @Charles @ Backbone Energy. Just picked up an issue regarding my BSL 6.4kw battery which is connected to the 8kw Sunsynk inverter. For the second time within a month, the battery completely depleted to 0%. It then recharged and continued to work normally. My setting for the battery to shut down is 20%. Not sure if this is a similar issue that @Daniemj had experienced. Is there a way to resolve this problem from reoccurring? My installer has no idea what the issue could be. The system worked with no issues prior to this for 6 months. Thanks

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