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mikisound asked

SmartShunt - inaccurate current measuring

Hello,

I have a small off grid system which consist from the followings:

  • Solar panel 340W / 24V
  • SmartSolar Charger MPPT 100/20 (v1.54)
  • SmartShunt 500A (software version v4.05) with Temperature sensor (ASS000100000)
  • Rospbery PI 3 (software version v2.63)
  • Battery Banner EnergyBull 12V 100Ah (C20); Absorption voltage 14.5V; floating voltage 13.5V

DVCC is enabled on the RPI while the Smart Networking is disabled.

During the night the SmartShunt shows a consumption of app 1.3A while at the same time the Charger is showing a consumption of only 0,8A. I have only DC loads that are connected to the charge load output. The only exception is the supply of the SmartShunt, which is connected directly to the positive pole of the battery via the temperature sensor.
The SmartShunt was calibrated as described in the manual.
The SOC is during the night dropping down from 100% to approximately 84,3%. With settings I have managed that the SmartShunt synchronized at the end of the absorption phase. At the moment, of synchronizing the SOC is showing a value of approximately 90,3%.
if a am calculating the SOC with the current shown on the Charger the SOC would drop down app. to 90% and the synchronization would happen close to 100%. In my opinion, the current measured by the SmartShunt is NOK while the current measured by the charger is OK. Also, if I am looking on the discharging and charging energy values over a period of time the discharging energy is double higher than the charged energy.
The second think what I have observed is that during the floating stage of the charger the SmartShunt measure a negative current? This is another reason I think the SmartShunt measures a higher current than it does in reality.

1617220667195.png

Any Idea how to solve this inaccurate measurement?

SmartShunt
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2 Answers
JohnC avatar image
JohnC answered ·

Hi @MikiSound

This reeks of an incorrect Zero Current Calibration. You may well have done it before, but maybe since have hit that button by mistake while some current was flowing. Easy to do, and of course you won't remember if you did.

Actually lift the cable from the shunt to be certain.

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mikisound avatar image mikisound commented ·

Thanks @JohnC for the advice. I have calibrated the SmartShunt again by disconnecting the cable from the terminal that is going to the system. After that the VictronConnect application showed 0A. Unfurtunately after plugin the cable back I have still this discrepancies between the Charger and the SmartShunt. So, the Zero Current Calibration is not the reason :-(

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mikisound answered ·

Update:
After a lot of different tests that I have performed, I think I have finally found the reason for the false measurement of the SmartShunt.

The SmatShunt was placed right next to the MPPT Charger and the Raspberry PI. After I took him away from them it started to show the correct value.

The only logical explanation for me is that there was interference between the SmartShunt and the MPPT charger or RP.

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