Battery draining while unconnected

[ThreeDotOneFour]

A while ago I assembled a 16s LiFePo4 100Ah battery pack. I charged it up to about 60% SOC and left it without having anything connected to it except a daly smart bms. Now about a month later I found out the battery had drained all the way down to about 20% SOC. This equates to a continuous draw of about 50mA. The LiFePo4 cells are encased in a aluminium box, thus I feared there would be some kind of leak via the walls of the casing, however doing some measurements showed this wasn't the case. Therefor I think something is going wrong in the daly bms. I've attached a screenshot of the daly bms app homescreen. The SOC in the screenshot is incorrect since this was set after the charge up to 60% SOC and during this slow draining the SOC is not updated. Does anybody know what might be going wrong here?

 

[BentleyJ]

50mA is 0.050A. Lets do the math.
0.050 x 24hrs = 1.2Ah per day
1.2 x 30 = 36Ah for the month
100Ah battery at 60% SoC is 60Ah stored and available in the battery.
60Ah - 36Ah = 24Ah remaining after a month with the parasitic BMS load on the battery.
You estimated the battery had been discharged down to about 20% SoC which correlates extremely well with the above calculated SoC of 24%.
The electronics on the BMS are not FREE, 50mA as you mentioned, is about what one would expect. There is always a small draw on the battery to power the microcontroller.
The SoC % as reported by the BMS did not change because either power used by the BMS is so low that it is less than the threshold of the Least Significant Bit of the ADC or the electronics are powered directly by the battery via an internal connection that does not pass thru the shunt.

Does not sound like you have a problem at all.

 

[ThreeDotOneFour]

Alright thanks for the answer! I thought the powerconsumption of the BMS was rather high since the data sheet of the BMS stated the selfconsumption would be in the order of micro Amps. However if a 50mA current draw is normal for a BMS than im reassured that everything is fine

 

[BentleyJ]

For the record, I don't use a Daly BMS myself so do not have any first hand experience with what is normal usage for that brand. That said, I have measured current draw on other BMS brands and Active Balancers. Based on those tests, 50mA doesn't seem out of line.
The BMS may in fact have a low power mode or standby mode that only uses microamps but when its ON, performing cell monitoring, shunt monitoring, temp monitoring and has both charge and discharge FET's enabled there is a small amount of current flowing all over the PCB to many areas, it adds up.