Electrodacus SBMS0 and shunts: Did I miss something ?

Hi everybody ! A little question to the Electrodacus fans:

I've designed a simple system on my sailboat, pretty close to the one described in the SBMS0 documentation, with 2p4s cells, 4x170W PV, 2xDSSR20, SBMS0 and the 2 shunts. Nothing fancy there. Everything works fine but the measures from the shunts are rather strange....

The 2 shunts are identical, 200A 75mV, in series, with the load in between.

So, with no load, I was expecting to have identical values on the two shunts. But I don't... The Battery value displayed is different and way too high. I suppose this value should be just like Battery = PV - LOAD


(PS: when I took the pic, a little load was actually applied but that doesn't change the issue)

But if I apply a load, the values are coherent, even if the battery value is still not realist (in this case, the load was around 70A) :


The shunts are auto-calibrated after the first full charge by the SBMS0 and I didn't find any setting.
So... I suppose I've miss something or didn't do the proper setting. But honestly, I wonder where I messed up....
Any idea ?

Ahh, I think you are wrong about "auto-calibration" It calibrates its internal use, not the shunts. In the newest SBMS0 Manuel Step-4 page 7 defines how to calibrate the shunts. I would suggest a clamp amp meter if you want it accurate. (especially if you used cheap shunts)

grizzzman said:

Ahh, I think you are wrong about "auto-calibration" It calibrates its internal use, not the shunts. In the newest SBMS0 Manuel Step-4 page 7 defines how to calibrate the shunts. I would suggest a clamp amp meter if you want it accurate. (especially if you used cheap shunts)

Click to expand...

Yep, you're right. The SBMS0 adjusts itself and the shunts stay what they are... In my case, both are 200A 75mV. It's may be not a perfect choice for the PV as I'm loosing accuracy. But I don't care as long as I have an approximate and coherent value. And that doesn't explain the values displayed by the SBMS0. Needless to say I've checked the polarities and tried to switch them just in case... ( wasn't the best idea ever...). The values with a clamp amp meter have nothing to do with the nonsense from my SBMS0. That's why I'm still considering some calibration or parameters. But where ???? Till now... no idea...

Fixed !
Dacian, the designer of the SBMS0 contacted me through its GoogleGroup to give me the answer.
I wrongly interpreted the documentation while saying the SBMS0 automatically calibrated itself on the shunts value.
Actually, you have to enter the resistance of your shunts in the ADC menu. It's explained page 39 in the v03d manual.
Everything works fine now, the Electrodacus solution is a really cool stuff and I'm the happiest man on earth !!!...
Thanks everybody for your help.