SoC spiking up and down

Last night I set a scheduled charge to 60% ending at 05:30, but woke up to find the batteries at 25%.

Then the sun came out and they seemed to be charging very slowly. But then, mid-afternoon, one minute they were at 69%, literally a minute later at 100%.

Looking at the SoC graph, the SoC plummeted when the scheduled charge ended, despite the fact that there was only background load.

The mid-afternoon upward spike is very apparent. There was also a small downward spike mid-morning - again with very little load.

Have attached all the graphs. Would love some insights.

With thanks in anticipation.

Graphs.jpg

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matt1309 commented · Jun 15, 2023 at 10:10 AM

What's monitoring your SoC in your system? Spikes in SoC seems to correspond to spikes in current (and more likely the spike in voltage) although battery voltage stabilises yet SoC takes a hit.

It's almost as though SoC monitor is relying on voltage to measure SoC and when voltage spikes in either direction SoC updates when really it probably shouldn't.

Guessing this isn't a smart shunt and maybe BMS with some not so good SoC monitoring? Smart shunt might be the answer to your problems.

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menneer matt1309 commented · Jun 15, 2023 at 10:34 AM

Thank you for your reply. I don't know exactly what is monitoring my SoC. I have a Quattro and a Venus without any modifications as far as I am aware.

This issue has only occured once to my knowledge and as long as it isn't a sign of battery or system degradation, I am happy.

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matt1309 menneer commented · Jun 15, 2023 at 10:43 AM

It might be. However it seems what's monitoring the SoC is more likely the issue. If you've not got a smart shunt installed then my guess would be it's the BMS (battery management system). If it's only occurred once (and not persisted) it may have been a bug with BMS. A complete system shutdown/reboot might resolve it.

If it was battery degradation I would expect the voltage drop to be disproportionally large amount under load. You could test this by monitoring battery voltage when under load. If the battery voltage drops really low then it might be signed of battery degradation. However I dont think SoC monitor would "know" this which makes me think it's SoC Monitor rather than the battery.

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