Daly BMS stopped working

Hello,

Good day and happy Thanksgiving to those in the US. I need some help / guidance on my recent Daly BMS purchase. I purchased it from Aliexpress. Its an 8S 200A common port Daly BMS. Its connected to a 24V pack, and I am using a cheap 2000W continuous / 4000W peak 24DC-220AC inverter. I received the BMS 2 days ago, and since installing it in my setup, it has been working OK, I think. I knew its working because I get the same voltage when I test using multimeter from main positive of my batt to main negative, then main positive to P- of the BMS. That was until a few hours ago.

I noticed that my inverter went off. I only had a 15W mobile phone charger and a 150W laptop connected to the inverter. I checked my battery pack voltage, and it still had 23.7V left. I then checked from main positive of battery to P-, and I only got 9.1V.

I specifically chose 200A because at 24V the inverter running at 2000W will only draw 83.3A (2000W / 24V), and at peak 4000W, will draw 166.6A, so I have plenty of headroom, if my calculations are correct, if not please let me know.

I am dealing with the seller right now through aliexpress to get a replacement. Has anyone had any success in getting a replacement for cases like this? Is this a rampant issue on Daly BMS?

Thank you in advance for your inputs.

23.7V is a VERY low state of charge especially for such a low load. That's an average of 2.96V/cell. There is very little capacity remaining at that level. If you measured 23.7V AFTER the inverter had been shut off after awhile, i.e., you didn't notice it right when it happened, your batteries were likely at an even lower voltage/state of charge, and your BMS or inverter may have shut off due to low voltage.

Could one of your cells have hit the LVD?

snoobler said:

23.7V is a VERY low state of charge especially for such a low load. That's an average of 2.96V/cell. There is very little capacity remaining at that level. If you measured 23.7V AFTER the inverter had been shut off after awhile, i.e., you didn't notice it right when it happened, your batteries were likely at an even lower voltage/state of charge, and your BMS or inverter may have shut off due to low voltage.

Could one of your cells have hit the LVD?

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This is embarrassing. It appears you are correct. A few minutes after I posted this thread, my replacement battery arrived. That's for the one that puffed out (story from my other post). I removed the not-so-puffed battery and replaced it. Charged the pack, and BMS came back to life.

Sorry to bother you snoobler, and thanks. Have a great weekend sir!

GerardJacinto said:

This is embarrassing. It appears you are correct. A few minutes after I posted this thread, my replacement battery arrived. That's for the one that puffed out (story from my other post). I removed the not-so-puffed battery and replaced it. Charged the pack, and BMS came back to life.

Sorry to bother you snoobler, and thanks. Have a great weekend sir!

Click to expand...

It’s completely normal for a Daly BMS to behave like this - not a fault at all!

The BMS will go into “sleep mode“ and switch itself off so it protects the battery against further discharge. When this happens the voltage at the P- lead will float and the voltage reading you see on your voltmeter be less than battery voltage.

This sleep mode happens if one cell hits LVC or if there is no charge or discharge sensed by the BMS and the sleep timer setting is exceeded. wake the bms again by charging the pack with at least 0.6V higher on B- than P-.