Daly Smart BMS current reporting inaccurate

[dcawkwell]

I have installed a 150a 16cell 48volt Daly BMS but the Daly is reporting inaccurate current readings eg 10a 20a 30a 5a etc for a steady 20a load. I also have a 12v lifepo4 battery with a Daly bms and the current is
rock steady with a steady load. I notice the current direction is reversed -negative for discharging and +positive for charging but the 12v battery is the reverse of this. I thought it might be a faulty BMS so I tried another Daly BMS but this is doing the same. I have tried the zero current caibration on the Smart BMS app but this hasn't made any difference.
Any idea what is wrong.

 

[tabascoz]

Hi there, are you sure the bms wiring is right? B- wire is connected to the battery and P+ wire is connected to the loads? I've heard of this symptom when wires were inverted.

Cheers,

 

[rbeudel]

It may be a firmware problem when using a inverter as charger. If it is, try to get a inverter Firmware for your bms.

 

[MaxG]

I can report the same thing. I have a 250A Daly BMS, where both, cell and current voltages fluctuate significantly.
It has an internal balancer, which can't be switched on either. Here the difference between the Daly and another brand BMS for the V measurements.


The V in the cells doe snot fluctuate at all when measured with a Multimeter under constant current... and it the V measured, does not reflect the V indicated by the Bluetooth app.
In addition, I cannot switch on the balancer in the Daly.
My conclusion: get rid of the Daly. I am waiting for the JK-BMS v10 to be released soon, then make the switch.

 

[tabascoz]

Hi there, agree about the crap balancer of Daly BMS, but on the readings, I have pretty stable readings for both global battery V and cell V. What does fluctuate is bat current. It is not steady, however the SOC measurement is very good and my experience, after proper calibration is very positive. It only drifts for about 10% in one week of cycling IF I don't hit the bottom or top charge. Whenever i hit one of them, it self's reset.

I do not use, however, the Bluetooth dongle to get BMS data. I use an esp32 / esphome connected by serial.

 

[Skypower]

Wild current readings is why mine has a second life as a doorstop.

 

[MaxG]

I have pretty stable readings

Hmm, looks like you capture data every minute, which makes it look stable. Also, the 50 mV scaling makes it look stable too.

Wild current reading

... yes, really bad. To explain the graph; I used to have one battery on the inverter/charger. I then connected a second, older set in parallel. So for this graph, I took the inverter's reading and subtracted the Daly value, to the Zeva portion of the current. This used to absolutely stable; e.g., a 1 kW load was ~20 A flat, as long as the load remained the same. The Daly sends wildly fluctuating values, which is smoothed in this graph with a 3-value average being graphed; otherwise it would look worse. --- Yes, it has to go.

 

[tabascoz]

Hmm, looks like you capture data every minute, which makes it look stable. Also, the 50 mV scaling makes it look stable too.

Right and right, but i am indeed capturing every 10s and the scale of the screenshot was the default from Grafana -that's easy to change.
I have three digit decimal resolution, how about yours ? I can change it to match and see how it goes.

 

[tabascoz]

here it is, looks way messier now...



It's undoubtedly present a noise amplitude of around 0.05v. Do you have practical reasons for getting down to this resolution? Reason I'm asking is that i would like to understand if i am missing something myself.

 

[MaxG]

My Zeva BMS has a 1 mV resolution... with cells Vs going in the same direction; the Daly has Vs that go in opposite directions; go figure.
The longer I look at this, the quicker I want to get rid of the Daly. However, what might be worthwhile at my end, is to disconnect the Daly active 5 A balancer, and see, if the Vs are still this jumpy. But, it shouldn't balance under 3.4 V for starters.

 

[tabascoz]

I do have the 5a also connected, let me know pls the results cheers