Problems with Daly BMS

I have a 120A 8s Daly BMS that manages a 24V LiFePO4 battery with 16 cells top-balanced at 3.45V. The BMS is totally dumb, in fact there is no way of knowing whether it is operating or not, apart from the fact that the battery is connected to the inverter (the inverter therefore sees the battery, which means tsome part of the BMS is working). I am pretty unhappy with the cell balancing. Documentation for the BMS (or any Daly equipment as far as I can see) is virtually nonexistent. At the end of the charging cycle in afternoon the voltage difference between the lowest cell voltage and the highest cell voltage is up to 350 mV. Since the BMS does no reporting at all, I build a logging system that monitors several battery parameters, including cell voltages. I attach a plot for a number of days in July this year. You can see that the balancing appears not be running well at all. However I have not other experience with LiFePO4 cells or inverters and I have no other experience to compare my measurements to. I would appreciate comments on a few points:
1) Do the battery voltages appear usual at all?
2) If not, is there anything to do?
3) If the BMS needs replacement, would you replace it with a Daly again?
4) In case of replacement, is there any other reasonably-priced BMS available that is reliable? Our low exchange rate in South Africa causes all imports to be incredibly
expensive.

Kind regards,
Willem Ferguson

Willemf said:

I have a 120A 8s Daly BMS that manages a 24V LiFePO4 battery with 16 cells top-balanced at 3.45V. The BMS is totally dumb, in fact there is no way of knowing whether it is operating or not, apart from the fact that the battery is connected to the inverter (the inverter therefore sees the battery, which means tsome part of the BMS is working). I am pretty unhappy with the cell balancing. Documentation for the BMS (or any Daly equipment as far as I can see) is virtually nonexistent. At the end of the charging cycle in afternoon the voltage difference between the lowest cell voltage and the highest cell voltage is up to 350 mV. Since the BMS does no reporting at all, I build a logging system that monitors several battery parameters, including cell voltages. I attach a plot for a number of days in July this year. You can see that the balancing appears not be running well at all. However I have not other experience with LiFePO4 cells or inverters and I have no other experience to compare my measurements to. I would appreciate comments on a few points:
1) Do the battery voltages appear usual at all?
2) If not, is there anything to do?
3) If the BMS needs replacement, would you replace it with a Daly again?
4) In case of replacement, is there any other reasonably-priced BMS available that is reliable? Our low exchange rate in South Africa causes all imports to be incredibly
expensive.

Kind regards,
Willem Ferguson

View attachment 22513

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Hi Willemf

I have recently purchased a Daly BMS and theyt send me some documentation which I have attached below. Hope this helps.

Regards

thedodgersonline said:

Hi Willemf

I have recently purchased a Daly BMS and theyt send me some documentation which I have attached below. Hope this helps.

Regards

Click to expand...

Thank you very much. Really appreciated.
Kind regards,
willemf

Hi Willem

I have a 120A 8s Daly BMS that manages a 24V LiFePO4 battery with 16 cells top-balanced at 3.45V.

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I don't have a 8S installation like yours, but I had a similar issue with a 12V 4S setup.
One cell was running into high voltage, over 3,75V while the other 3 cells are far below 3,5V
I could simply solve the issue by top balance the cells at 3.65V.
I assume my cells I got from Aliexpress, with about 30% charging capacity, where never top balanced.

1) Do the battery voltages appear usual at all?

Click to expand...

Looking into your diagram, a reason can be bad cells, or still not well top balanced cells, as far as I know.

2) If not, is there anything to do?

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You wrote, you top balanced at 3.45V.
I would suggest to go to 3.65V if this is your cell specification as well.
These videos from Will Prowse helped me:

Also I was lucky that I had 2 caravan projects.
So I was able to compare all 8 cells, and put just these 4 cells together who are close to each other for the charging curve. ;-)

3) If the BMS needs replacement, would you replace it with a Daly again?

Click to expand...

Personally I'm still with the Daly 4S BT/UART version, using a 3pin USB Monitor cable to configure the BMS,
with the Sinowealth Software and the BT Module, just to monitor. ... for a reason:

I had several more expensive Liontron LifePO4 Batteries before, they are using inside a xiaoxiang BMS.
I was not happy with this BMS, because I was not able to configure the Charging MOS seperate
from discharging MOS.
eg. One Liontron Battery disconnects completely at 14.2V, because one cell inside was bad or
not balanced. Then the Discharging was sadly blocked by Xiaoxiang BMS in this moment as well.
I had to wait until the battery voltage is falling down by itself below 13.99V, takes about 15min.
Such complete power outage was not acceptable, (consider a fridge in a caravan...) so I moved to Daly & DIY LifePo4.

The bad side I see with Daly, every BMS I got so far is a different version on same model/order and seems not well configured.
- like allowing charge with 300A, while it should be only 100A allowed ...
- allowing charge on -70°C ... is a bad idea for LifePo4
- CutOff voltages far from LifePo4 spec or just at the border Limit of LifePo4 chemistry
- also it is better to test the temperature sensor, if the charge cutoff really works
- configure the discharge MOS to still operate, when the charge MOS will cutoff for a reason.
Daly seems to me not a "Plug and Play" device. ;-)

Cheers,
Andreas