I received my SBMS0 yesterday, after dealing with customs. First of all: THANK YOU. This little thing is an awesome device. And it's worthy to mention how well you build these units. The quality is outstanding!
I have built a test setup to try out the basic functions and familiarize myself with the abundance of options. The setup is simple: 4S Li-Ion pack (10 Ah) connected to bat shunt (250 A / 60 mV) connected to an Juni 406 B RC charger (simulating load or charge source). GND of battery is directly connected to the charger in this setup. Only ADC1n/ADC1p connections besides the cell wires. Nothing else.
Everything is working finde. There is just one quirk I can't wrap my head around: The current values measured by the bat shunt sometimes seem to be off.
Example: The charger charges with a current of 4,5 A. The shunt only measures 3,5 A (so around 1 A less than real current). Now I switch to discharge with identical current (4,5 A) and the SBMS is showing a discharge current of 8 A+. Both currents verified with clamp multimeter (around 4,45 A).
The ADC calibrated with a zero value (or neutral value) of 32749 steps accord to diagnostic menu. I tried re-starting / re-calibrating the device multiple times and variants: 1) Charger connected, but no current flowing, of course; 2) nothing connected to load side of bat shunt.
I got it working for a two single attempt and readings were correct. The second time I managed to almost get in a full charge / discharge cycle (around 4h working time). On the last few Ah of the charging cycle the SBMS0 started showing the "wrong" values again. Nothing changed for the setup - as far as I can see.
The resistance for the shunt is set to: 0,06 V / 250 A = 0,24 mOhm. While it was working correctly, I trimmed the resistance just a little bit above that value to get accurate readings.
To check if the shunt is okay, I repeated a discharge with 2A and charged with 2A (while SMBS0 NOT connected) and measured the corresponding voltage drop on the shunt, which was identical but reversed in polarity both times. So seems okay, too.
Is there anything I am missing? Is the wiring of the ADCs really sensitive? Maybe you can push me in the right direction... :)
Thanks again and best regards,