question

gawan avatar image
gawan asked

Continous Power Drops from MAX to zero ?

Hi,

my system consists of 3 x Multiplus II 3000, two MPPT250/100 (16x330 Panels each) and one MPPT250/60 (8x330 Panels).

In total I have 13kW (three compass orientations) on 3 Inverters with 8500-8700 W max.

Whenever my system reaches max power (approx. 8700 Watt), it drops down to 0 W for a few seconds, goes back app to MAX, drops again and continues this behaviour as long as it is close to max power.

The green line is the total output of the system and as you see it jumps from 8800+ down to zero again and again and again.

Is the panel power outage too high ? Do I have to / Can I limit PowerMAX of the MPPTs ?

Shouldn't this be done automatically by my Inverters ?

BR

Gawan


Multiplus-II
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3 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

What size and type of batteries do you have?

Can you check to make sure there is good connection between the batteries all the way to the inverter terminals (fuses intact, nothing is loose)?

Check your graphs in the Advanced section to VRM to make sure that battery voltage is remaining consistent and stable under load and under charge.

If it varies, there could be an issue with the DC wiring, or the batteries themselves.

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gawan avatar image gawan commented ·

I am using 4 pcs quite old and used lead-acid batteries with a total of approx. 1,2 kWh.

This is not the reliable longterm solution, but a "hotfix" to allow me to start my Victron Infrastructure.

I do not want to draw and load energy to them - they should just allow me to run the system. Thats why I set the To-Be-Load-% to 100.

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ gawan commented ·

This is most likely the cause of your issues.

I expect if you investigate the DC voltage of your system during these drops in production that it is not stable. For example, the battery is totally full, there may be some change in conditions to increase solar production, e.g. a passing cloud, and then there is a sudden spike in the DC voltage. When the DC voltage is going up very high, very quickly, beyond the target DC voltage, the system responds by reducing the solar production.

I understand that you want to fully export, but the Victron system needs a stable DC voltage to operate reliably.

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gawan avatar image gawan Guy Stewart (Victron Community Manager) ♦♦ commented ·

Does it make sense to set the load target for the batterie from 100% to a lower value, like 80% ? So that there is still some buffer for DC peaks?

Passing clouds are not the issue - we had two perfect clear days yesterdays and the days before and as soon as the system reached 8500W+ (around 11:30) the issues began ... and stopped when it went down below 8500W again. (around 13:30)

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ gawan commented ·

Yes, It might help if you reduce the target voltages and configure the system so that the batteries do not fully charge, but instead have capacity available to buffer and absorb any changes.

Though it also might not be possible to correct the situation of such a large PV array on such small batteries.

Have you looked at the system DC voltages to see if my theory is correct?

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gawan avatar image gawan Guy Stewart (Victron Community Manager) ♦♦ commented ·

Unfortunately I do not know how to check the DC voltage.

Should I measure it directly on the battery (on one cell)? Or check a single MPPT DC voltage via console ?

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ gawan commented ·

It is logged to VRM in the Advanced section.

I demonstrate in this training video:

https://vimeo.com/373565023

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gawan avatar image gawan Guy Stewart (Victron Community Manager) ♦♦ commented ·

Ah ... thats you in the video ... nice :)

I will have to take a few hours and watch all of them.


I found the graph in the advanced tabs - unfortunately the data is updated every 15 mins only - that frequence is too low to see the drops or see the voltage peaks in detail.

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Guy Stewart (Victron Community Manager) avatar image Guy Stewart (Victron Community Manager) ♦♦ gawan commented ·

It is possible to increase the frequency of the updates to 1 per minute in the VRM menu of the GX device settings menu.

Then you can zoom in for more detail.

Try that first. If that STILL isn't enough resolution - there is another tool possible...

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gawan avatar image gawan Guy Stewart (Victron Community Manager) ♦♦ commented ·

Quick question: I am using MQTT already to get data from the system every second. Do you know the right MQTT key for this value ?

That would make it really easy for me :)

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klim8skeptic avatar image
klim8skeptic answered ·

3 x 3000w multiplus II, 3 x mppt/13kW array, on a 1.2kWh battery is never going to be a stable system.

The battery certainly can not handle the charge currents, or the discharge currents.

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chebanov avatar image
chebanov answered ·

I have the same situation with my MPPT 100/200. I'm using LiFePo 48V 100Ah battery with built-in third party BMS (not connected to CCGX). My max solar power can be around 1.8 kW. Total load equal 300W. When the solar power goes above 800W it drops every 20-30 seconds to 0. Have you found a solution

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samurai avatar image samurai commented ·
Just a 'me too' message. In my case an easy solar II gx 5000 , 2 times US5000 pylontech battery and 4800 wp solar aray.
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janieronen avatar image janieronen samurai commented ·
Could you show advanced page graph about battery voltage & current and solar production in a same picture? What is SOC during time when solar production is ramped down? Two US5000 are close charge limit with 100A MPPT. Have you checked pylontech cell level SOC? As if one cell is over voltage during max charge it will throttle charging down.
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samurai avatar image samurai janieronen commented ·

Seems the 'advanced' graphs are not detailed enough to catch the 0w ehh lows. You can see them when you look in the Dashboard. But I do monitor the system in Home Assistant and there you see the drops:

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There are no alarms shown about the battery and the min and max cell voltage only differs by 0.04V

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