question

maxoffgrid avatar image
maxoffgrid asked

10% drift in SOC calculation each day

System details:

  • EasySolar-II GX, 48v/3000VA
    • SmartSolar Charger MPPT 250/70 Firmware version v1.59
    • MultiPlus-II 48/3000/35-32 Firmware version v490
  • 2kw panels + good sunlight :)
  • 48V 100Ah (4 x 12v 100Ah GEL VRLA batteries)
  • No grid or generator connected.
  • No smartshunt used.

Problem in SOC calculation:

  • 10% downwards drift in SOC calculation each day observed after changing configuration from ESS to Hub-1. (Though there is enough sun light to charge the battery.)
  • The system is not connected to grid and MPPT always stayed in bulk mode while using ESS mode. Battery voltage stayed at 57.6V during sun hours as per bulk mode settings.
    • Configuration was modified from ESS to Hub-1 on 16th sep 11am. (Marked in yellow line in below graph)

1663645247731.png


  • Post ESS to Hub-1 change, bulk->absorption->float mode is reflected in MPPT state.
  • But SOC calculation is showing a downward drift each day by 10%

Question:

Is there way to correct the SOC drift without smartshunt?

SOC
1663645247731.png (98.4 KiB)
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1 Answer
nickdb avatar image
nickdb answered ·

Unfortunately, if you don't use an external shunt it is going to drift in a solar environment.

Shunts are more accurate and, properly set, will sync the soc to avoid drift over time.

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maxoffgrid avatar image maxoffgrid commented ·
Can the drift be 10% on every day? In 3 more days, SOC would be showing 10%.


Is it possible just such adjust the known heavy value drift in SOC, since we do know that battery goes to float state.
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nickdb avatar image nickdb ♦♦ maxoffgrid commented ·
Indeed it can drift that much. The internal meter has no visibility of the mppt and you can't set it to sync, unfortunately it's normal.

I have seen worse, prior to a shunt being installed.

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maxoffgrid avatar image maxoffgrid nickdb ♦♦ commented ·

Unfortunate to know there is no communication to adjust frequently observed anomalies. Though I could see all logs from different components in single VRM portal, which also can talk to the device to adjust settings.

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