SoC jumped to 100% while the battery was being discharged

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elel asked Dec 31, '21

SoC jumped to 100% while the battery was being discharged

I have the following simple setup with ESS Assistant in which I charge the battery from the grid during low rate period at night and then use the battery for the house loads during day time.

I encountered a problem in which the SoC shown in the VenusOs screen jumped from 69% (Main On+Absorption LED “ON”, Inverter On LED “Blink”):

suddenly to SoC 100% (Main On+float LED “ON”, Inverter On LED blink):

while the battery was being discharged!

The battery pack has its own BMS and the BMS has no connection to the MP-II.

I set the "State of charge when Bulk finished " to 90% in VEConfig and it worked properly.

I set the "Minimum SoC (unless grid fails)" in ESS to 10% and it worked properly.

The “Float Voltage” set in VEConfig was 52V. The above problem occurred at 53.2V .

Any advice on:

Why the Float LED suddenly lighted up?

Why the SoC suddenly jumped to 100%?

SOC

configuration-diagram.jpg (59.5 KiB)

soc-jump-1.jpg (13.8 KiB)

soc-jump-2.jpg (13.6 KiB)

3

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Paul B commented · Jan 01, 2022 at 02:50 AM

Hi we would need more setup information to be bale to help you

Please send setting pictures on the Muttiplus ve configure settings one screen shot for each of the screens - also in the GX please send the system setup setting showing the battery monitor selected

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elel Paul B commented · Jan 01, 2022 at 10:53 AM

Thanks a lot for the response. Below are the settings exported from VEConfig:

TAB: General

System frequency 50Hz

Shore current 100.0 A

Overruled by remote unchecked

Dynamic current limiter unchecked

External current sensor connected (see manual) checked

State of charge when Bulk finished 90.0 %

Battery capacity 277 Ah

Charge efficiency 0.95

TAB: Grid

Country / grid code standard UK: G98/1 March 2019, G99/1 May 2018

LOM detection AC input 1 Type B (grid code compliant)

start P(f) at 50.40 Hz

start delay for p(F) 0.08 s

Droop for p(F) 10.0 %

Use Aux1 (if available) as disable FeedIn signal checked

Reactive power regulation Use a fixed Cos Phi

Filter time for reactive power 3.3 s

Cos phi at point 1 1.00

TAB: Inverter

PowerAssist unchecked

Inverter output voltage 230 V

Inverter DC shut-down voltage 48.00 V

Inverter DC restart voltage 50.00 V

Low DC alarm level 49.00 V

Do not restart after short-circuit (VDE 2510-2 safety) unchecked

enable AES unchecked

TAB: Charger

Enable charger checked

Weak AC input unchecked

Stop after excessive bulk checked

Lithium batteries checked

Configured for VE.Bus BMS unchecked

Charge curve Fixed

Absorption voltage 55.00 V

Float voltage 52.00 V

Charge current 70 A

Repeated absorption time 1.00 Hr

Repeated absorption interval 7.00 Days

Absorption time 1 Hr

TAB: Virtual switch

TAB: Usage

Virtual switch usage Do not use VS

TAB: Assistants

TAB: Assistant Configuration

ESS (Energy Storage System) (size:962)

*) System uses LiFePo4 with other type BMS

(This can be either a BMS connected via CAN bus or a BMS system in which the

batteries are protected from high/low cell voltages by external equipment.)

*) The battery capacity of the system is 277 Ah.

*) Sustain voltage 49.00 V.

*) Cut off voltage for a discharge current of:

0.005 C= 48.00 V

0.25 C= 48.00 V

0.7 C= 48.00 V

2 C= 48.00 V

*) Inverting is allowed again when voltage rises 2.00 V above cut-off(0).

*) Relevant VEConfigure settings:

- Battery capacity 277 Ah.

- PowerAssist unchecked

- Lithium batteries checked

- Dynamic current limiter unchecked

- Storage mode unchecked

Below is the screen for the "Battery Monitor" :

Here is the video showing the sudden jump to 100% SoC.

https://drive.google.com/file/d/16hqb87Ce6e9MNH_LlkQA6yIPiyxORBO8/view?usp=sharing

Look forward to your advice on this problem.

(Note: I also have some other problems encountered:

https://community.victronenergy.com/questions/113770/discrepancy-between-grid-setpoint-and-the-actual-p.html

I am not sure whether they are related.)

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battery-monitor-automatic.jpg (35.8 KiB)

elel commented · Jan 01, 2022 at 07:10 PM

The same problem happened again today in which the SoC suddenly jumped to 100%SoC.

After the sudden jump-to-100%-SoC problem last night, the system failed to execute the scheduled charging after mid-night and then did a list of erroneous actions after that…… (but these are not the subject of this thread and I will handle them later, just in case they are related to this one).

I somehow was able to schedule the changing during daytime. The battery then discharged as expected but then jumped to 100% SoC from 80% just like what it did last night. Here is the link to a short video which shows what happened.

https://drive.google.com/file/d/1NUdbynsnhQS0EemTmcZi3BBPSp2uKSzK/view?usp=sharing

Any help or advice would be very much appreciated.

(Note: after the setup of the ESS, it was the 2nd time I discharged the battery from the end-of-bluk-charge status and in both cases this problem occurred.)

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Modifications Space

Node Red Space

Answer 1 · 2022-01-22T06:58:57Z

Paul B answered · Jan 22, 2022 at 06:58 AM

If you look at your video you will notice that it switched from Absorption to float on the multiplus loghts then the SOC flipped to 100% -

So I would think that the Multiplus was ending the absorption phase of its charging cycle as its held the battery voltage at 55v for 1 hr as set and is now changing to float mode of 52v, at that point the SOC is changed to 100% as the battery is full.

The small discharge is occurring because the absorption voltage is 55volts and float is 52 so you will see a negative amps figure until the float voltage reaches the set point set being 52 volts.

well thats my thoughts as to why

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