question

fm1 avatar image
fm1 asked

Quattro charging pattern

I need your thought


I have

  • 2x Quattro 48v 10000 in split phase 120/240v, connected to 48volts batteries.
  • The system is grid-tie, with no feedback to the grid and no PV.
  • The ESS is disabled.
  • A Cerbo GX is used and update to date.
  • The batteries BMS is linked to the Cerbo and handle the charging.


My question is:

It's normal, once the batteries are full, the Quattro kept charging continuously ? The Quattro generate a sound each time it switch between charging and no charging and I'm wondering if that could generate a excessive wear on the Quattro.

Here the video with the switching noise



Every 2-3 secondes it switching between, trying to slightly charge the batteries and stop.

cerbo-charge-discharge.gif


And during this time, if I look into the Cerbo to validate if any current goes into the batteries, everything stay at 0

1702310300718.png



Should the Quattro stop charging at some point ?


battery chargingquattro 10kva
cerbo-charge-discharge.gif (23.4 KiB)
cerbo-charge-discharge.gif (23.4 KiB)
1702310300718.png (18.9 KiB)
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2 Answers
snoobler avatar image
snoobler answered ·

"Grid tie" + "no feedback to grid" are mutually exclusive terms.


Placing grid input on a Quattro does not mean grid-tie. Grid-tie means grid interaction, i.e., you have a contract with your utility to backfeed to the grid.


You are off-grid with grid backup.


Your Pylontech battery is in control of the system. Unfortunately, the Pylontech battery is telling the system:


"Charge and hold my target voltage."


It doesn't know the concept of float voltage, so the Quattro is responding the only way it knows how:


  1. Target voltage reached. Charger off.
  2. Voltage drop. Charger on
  3. Repeat 1 and 2


This is normal behavior for the way you have your system configured.


What is your goal with this system?

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fm1 avatar image fm1 commented ·
Thank you for your reply @snoobler


The goal is to use the Quattro as a "UPS" for a part of my house. In case of grid (input #2) failure, that will switch automatically and transparently on the batteries and keep feeding most of the house for a while.


1) Using the grid as main source until a grid failure

2) Using the batteries to feed part of the house

3) Connecting a generator to refill the battries when required.

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snoobler avatar image snoobler fm1 commented ·

Set DVCC voltage limit to 54V. See if the behavior stops. This may be sufficiently low to prevent the BMS from triggering 0A CCL,and you should be able to attain a high state of charge.

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fm1 avatar image fm1 snoobler commented ·
Hi @snoobler

With the VDCC at 54v, it's much better. I still hear some charging, time to time, but not every seconds as before

If I use NODE-RED, I could configure a logic to set the VDCC max voltage to 54v as long as the SOC is 99 or more. If the SOC is 98 or lower set the VDCC voltage to 56 until the battery reach 56 volts then set the VDCC back to 54v until the SOC is lower than 98.

Will it make sens ?

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snoobler avatar image snoobler fm1 commented ·
The SOK battery is out of balance. If you can see the individual cell voltages, you will find that one or more is likely notably higher than the group.


I am not competent to comment on Node-Red. Once the cells are balanced, 54V will maintain 99-100%. If your goal is pure UPS operation, that's probably best. Periodic charging into the balance range (55.2V, 3.45V/cell) is a good idea to ensure cells stay balanced.


ESS is likely overkill.


As you may be aware, LFP cells actually degrade when held at 100% for extended periods. If temperatures are mild, it's not a major deal, but light cycling is better for them than holding at full charge.


You could use the programmable relay and general flag assistants, the Quattro Aux1, the Cerbo Relay 1, and the Cerbo generator control function to ignore AC input completely until 90%, then charge/power loads until 100%, then ignore AC again. You can also identify a quiet period where you can change the on/off criteria for that time as well. This can kinda approximate ESS functionality.



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fm1 avatar image fm1 snoobler commented ·
I set it to 54v since12hours and the batteries still reporting SOC of 100%
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snoobler avatar image snoobler fm1 commented ·
Set to 54.4 and evaluate if it cycles on and off.
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JohnC avatar image
JohnC answered ·

@fm1

What batteries are these? They're recognized as Pylontechs, but the Charge V is typical of 16 cell batts rather than 15.

Maybe they work like Pylons, so see this reference.. https://www.victronenergy.com/live/battery_compatibility:pylontech_phantom

You perhaps could try reducing Charge V in the Quattros so that the batt bms isn't 'slamming the door' on a V it can't handle?

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snoobler avatar image snoobler commented ·

SOK, EG4, Trophy, Jakiper, etc., "server rack" batteries use the Pylontech protocol for 16S instead of 15S. Native support was added in Venus OS v3.00.


When in control of the system, all devices follow the BMS settings for voltage limit, charge control limit (CCL) and discharge control limit (DCL). MPPT, Inverter/charger, etc., charge/discharge behavior is overridden by the BMS. Set to lower or higher voltage and the BMS values override.


The charge voltage is commanded by the BMS. Changing it in the Quattro won't do anything. The only way to override it is with a voltage limit in DVCC, and it will behave the same... just at a lower voltage.


Given that we completely understand what is happening, and that it's normal for the installation, once @fm1 gives us an idea of the desired system behavior, we can help achieve that goal.

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fm1 avatar image fm1 commented ·
@JohnC @snoobler

The batteries are SOK 48v 100ah in 16 cell

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