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puitl asked

Value of end-of-discharge/cut-off voltage: ESS without BMS and BMV

Hi!

I have an ESS (3x Multiplus 2, 2x MPPT, Cerbo-GX and DIY-battery (48V Lifepo4) > no BMV and BMS without any communication to Victron).

What is the end-of-discharge voltage of the system when setting discharge to SOC 0%?

voltage
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4 Answers
Alexandra avatar image
Alexandra answered ·

@Puitl

Inverter shutdown it what you set it at in the inverter tab. Or when your batteries shutdown if they are lithium and you set that one too low.

With ESS assistant this can be variable as there is a voltage set for each C rating drawn.

For some ideas there you can check out the compatible battery page for ideas, on how other manufacturers do that.

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puitl avatar image
puitl answered ·

@Alexandra
In my 3-Phase ESS the setting of the first Multiplus was little different compared to second and third Multiplus:

DC input low shut-down: 42 - 44 - 44
DC input low restart: 46 - 46 - 46

Yesterday before going into this "discharge-night" my SOC was due to another problem way to high:
I have set my absorption-voltage to 55,4V (= 3,4V per cell). When there is much generator-power and therefore much charging-current the battery reaches the 55,4V pretty fast.
So the SOC in VRM jumps to the set value of 95% (= SOC after bulk) and goes over to absorption - although the REAL battery-SOC is only at 30%.
(This isn`t finally a big problem because the ESS still charges the battery with high current until the battery is "real-full" and ESS has to reduce the charge-current. The battery is also getting the appropriate amount of Wh (watt-hours) - so battery gets full charged, only the SOC showing in VRM is wrong).

This night i started discharging with VRM-SOC 100% and real-SOC of about 50% and on 2 o'Clock in the morning the battery voltage drops down to 40,6V! and my BMS disconnect the battery because 40,6V = 2,5V per cell which is already the lowest voltage permitted for Lifepo4....I am sure the voltage of some cells was much lower :(


My question: Why doesn`t ESS stop discharge at reaching battery-voltage of 42/44V??

Could there be an error in the System because of the differents values (42/44) in the three Multiplus?

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Alexandra avatar image Alexandra ♦ commented ·

All phases must be set the same. Ess loaded onto all three phases.

But ess will make no difference if you are offgrid.

All the charge current divided by three over all the phases.

Have you done the training or read manual.

Get a bmv for accurate SOC. Your system it more complex and requires better monitoring. Voltage as you know on lithium means nothing in regard to SOC. It sounds like your batteries are not in balance so your batteries so bms shut down there.

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puitl avatar image
puitl answered ·

@Alexandra Now i read in the ESS-Manual that the "dynamic cut-off voltage" (6.3 in the manual) OVERWRITES all input low-settings in the inverter tab, so they are not operative.

In the ESS config the dynamic cut-off voltage is set at 40V so i have to adjust this in the ESS config :)

One last question: After adjust the ESS config in VEconfig for all three Multiplus, is it possible to load it up collected over VRM or is it neccessary to load it extra in every Multiplus with the MK3 USB-Interface?


Thank you so much!

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puitl avatar image
puitl answered ·

Loading up via VRM was succesfull :)

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Alexandra avatar image Alexandra ♦ commented ·
@Puitl

Nice one.

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