Dynamic ESS slow discharge on idle when reached target SOC

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kampfiltis asked Jan 10, '24

Dynamic ESS slow discharge on idle when reached target SOC

I noticed a very low discharge on idle when reached the target SOC because ESS #1 low SOC is not triggered anymore (in previous versions after reaching target SOC, the ESS#1 was triggered). In my setup the Problem is that the consumption from battery is too low and my BMS doesn’t take any notice of it. So, the battery is draining but the SOC stays untouched. So, the real state of charge is drifting over time and after a few days I get a problem with low cell voltages (have only little 5kwh battery). Dynamic ESS on and minimum SOC set to 75%. Target SOC at the moment of screenshot was 91%.

After switching Dynamic ESS off and set minimum SOC to 90%:

Is there a solution?

Thx for all your good work!

SOC dynamic ess ess discharging

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Answer 1 · 2024-01-17T22:56:52Z

jottt answered · Jan 17 at 10:56 PM

I am not sure right now, but I think I might have a similar issue. Just not sure if its Venus or the BMS to blame (or rather my misconfiguration).

I have my minimum SOC set to 20% in winter. The system charges daily to around 25-60%, never full, but a little each day. Then it usually delivers all power back to those 20% before it can recharge in the morning.

What happens here is: Over multiple days the battery voltage at those 20% decreases until the BMS cuts in for safety, but the VenusOS still shows the battery has 20% SOC. It actually happens with any minimum SOC I tried from 0% to 30%.

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kampfiltis commented · Jan 18 at 07:45 AM

Do you use Dynamic ESS? With "normal" ESS I have no problems, because ESS triggers the Low SOC warning and the MultiPlus in idle mode will use grid instead of battery. Idle power consumption of one MultiPlus is a little to less for my BMS, so BMS will not notice discharging until low voltage alarm is triggered...

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jottt kampfiltis commented · Jan 23 at 09:05 AM

No I don't. Just checked, it's off.

The issue reads just very similar to my problem: Something drains the battery, but neither the BMS nor the Victron notices or recalibrates until the BMS cuts off the power to protect the cells.

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