10% drift in SOC calculation each day

Question

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question

maxoffgrid asked Sep 20, '22

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)

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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Answer 1 · 2022-09-20T04:30:25Z

nickdb answered · Sep 20, 2022 at 04:30 AM

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.

3

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maxoffgrid commented · Sep 20, 2022 at 07:38 AM

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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