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alan-falck asked

ESS Active SoC Limit fluctuations


2 x MultiPlus-II 48/5000/70-48 Firmware v3.01 2 x BSL 6.3kW Batteries 1 x BlueSolar MPPT VE.Can 250/100 1 x BlueSolar Charger MPPT 150/35 rev3 Energy Meter ET340 (servicing L1 & L2 phases only)

Hi, I've noticed the Active SoC Limit 40% sometimes dips below the threshold (to 36%) for no apparent reason. It's a small fluctuation (acknowledged) but I'm keen to learn what the underlying cause may be. rk-ess-glitch.jpg

FYI There were no high loads or outages (load shedding) during these times.

Could an imbalance between L1 & L2 be a factor?

The advance graphs show a latency between battery voltage and current, could this be the cause? Any comment or ideas on where else to look welcome.

rk-ess-vi.jpg

I do acknowledge ESS is a dynamic and adaptive algorithm and some changes may be completely normal, just keen to understand ESS behavior better, thanks.

ess settings
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4 Answers
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nickdb answered ·

Plumstead, my old stomping ground :)

All things being equal, ESS should not drop beneath the minimum (or active minimum if you're using batterylife). Unless there is a grid issue.

Have you charted out the active limit and the set limit? Perhaps, if you're using batterylife, it is adjusting it lower during the cycle.

If there are no other conflicting settings, you could have run into a BMS issue, BSL used to have problems with SOC accuracy, so if it unexpectedly dropped, that would be a problem. At this point the system should still trigger ESS#1 and/or ESS#2 states on the console.

Anything else in the system like PV inverters?

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alan-falck answered ·

Thanks, Nick I have tried With & Without battery life doesn't seem to differ. I also did BSL firmware updates on both batteries

I have also noticed on another site (running 3 x 5kVA Multis and 20K of Freedom Won) batteries the ESS Active SoC Limit is set to 40% but the voltage was around 50% for a number of weeks, then dropped to the set ESS Active SoC Limit.

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nickdb avatar image nickdb ♦♦ commented ·

You can't really use lithium voltage as a guide for SOC, the curve is too flat.

ESS will automatically block discharge when it hits the minimum or BL active min. No exceptions. It will trigger the status codes I referred to.

If batteries continue to drain, either the limit has lowered, or the system is unable/failing to pull from grid.

Those are all supported batts so ESS shouldn't behave any differently.

If you are having a sudden drop in SOC, that should be easy to see.

e-tower and BSL use the same BMS, so have the same faults.

Zoom in on the SOC charts and confirm if there is a sudden dip in soc, if so then there is something iffy in the BMS.

If it is a gradual decline, it is something else.

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alan-falck answered ·

Q: Have you charted out the active limit and the set limit? are you referring to the voltages setup in VE Config ?

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nickdb avatar image nickdb ♦♦ commented ·

I would disable batterylife, it just is a pain in the Southern hemisphere.

You can make a custom widget using these parameters:

Edit, you can skip the SOC limit one, just active is fine, you will have to compare it to what you have manually set as a limit.

screenshot-2023-08-21-at-165317.png

It creates a chart like so:

screenshot-2023-08-21-at-165351.png

You will be able to see if batterylife is mucking with the minimum.

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alan-falck avatar image
alan-falck answered ·

No PV Inverters


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