question

peter79 avatar image
peter79 asked

ESS battery level charging and inverter own consumption

Hello I'm quite new and Victron system was started only few days ago. But I'm observing few unexplained situations. Maybe you can help me.

1. Battery ignores minimal SOC (set to 10%) continues discharge until 5%, then starts charging from grid with 4kW until it reaches 10% and then continues with cca 500W to charge until 13% and then starts again discharging.

1.1. I was thinking that when it reaches minimal SOC it will go to idle and stay there until charged by solar panels, what I understand wrong?

1.2. I was thinking that when grid charging is disabled it means battery is not charged from grid, what I understand wrong?

2. If I look at VRM portal I see Grid, AC loads, Battery, PV charger, but when I calculate the sum I miss 100 to 500W, is this own consumption of Victron equipment? (you can calculate from any of the pictures, discharging 'misses' 109W, Charging1 382W, Charging2 188W)

3. UPS functionality does not work, by power outage lights stay, but clock and remote switches got reset, is there a way to fix this?

My system: 16x IBC solar 450 Wp, 3x Victron Multiplus 5000 (three phase setup), 2x Victron MPPT 250/70, 1x BYD LVS 4kWh, 1x Victron color GX

Attached pictures:

Discharging.jpgDischarging: Battery discharging even under 10%
Charging1.jpgCharging2.jpgCharging: How the battery is charged from grid
Expected.jpgExpected: This is what I expect to see when battery is less than 10%, please compare with Discharging picture

Thank you

Peter

VRMBYDmultipus
discharging.jpg (75.8 KiB)
charging1.jpg (74.1 KiB)
charging2.jpg (80.7 KiB)
expected.jpg (5.4 KiB)
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3 Answers
mysik avatar image
mysik answered ·

The info provided by @Alexandra is not accurate in few points!

Ad1. If your system is configured as ESS, then the Victron will allow to discharge to your SoC limit, and then will turn into Discharge disabled mode. Which means that there will be no DC-->AC inversion. But if you have DC load, it will not stop further discharge. So for example if your battery is idleing your BMS can still pull DC current (if it is powered up by DC side of course) which means that over time it will discharge battery more.

Ad1.1 If the SoC will drop 5% below your SoC limit, the Victron will start charging again (using grid if available) to top up to the SoC limit.


Ad1.2 The system is designed that if SoC drop 5% below your SoC limit or you are below SoC limit for more than 24h then it will slowly charge (using available source, including grid) until lower limit is reached at which point it will switch again to "discharge disabled"

Ad2. There is no 100% efficient systems, you have losses and the system consumption in the missing power. Charging 1000W from AC means you will get less on the DC side, and inverting 1000W from DC means you will get less on the AC side.

Ad3. Multi is capable to switch the power in less than 20 milliseconds, are your loads connected to AC Out1 (critical load) of the Multiplus?

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peter79 avatar image peter79 commented ·
1.1. Not sure If I have seen this somewhere described in this detail, but how it is possible that other systems have much less? For example my brother has similar setup from different manufacturer and it stays on 10% for weeks, with Victron 10 to 5 % drop is in 3-5 hours.

I do not have any DC loads, if there are any they are 'Vicron own' and I would expect they are under control of Victron (in another words my expectation was that when battery hits 10% it will behave the same as if it hits 0% - no current supplied out of battery)

1.2. If I set the charging to be disabled then still my expectation is that it will be disabled, I can maybe understand slow charging as you write, but do you think that 4kW is slow charging?

2. Fully understand, I was just surprised that own consumption is that high in average I see cca 300W

3. This is partly my fault, because I have not deeply studied and have expected that Victron is on-line UPS, but it is offline. Until now one outage covered, one not and one described below


Last story with Victron: I had contacted Victron to help, they have forwarded to local seller, this seller contacted my installer (very skilled person, nice work, great communication...) to tell him that he does not know what he is doing and that customer me is compaining on him! This is total LIE I was complaining about Victrons not working as expected and I was VERY positive about my installer, because I phoned cca 10 other installers and nobody wanted install Victron, saying: "...because it is problem...", "...it does not work in 3 phases...", "...no support from Victron..." ... He was the only one saying that he is willing to do it. The seller then asked to access to my system and as penalty for compaining has shut my house down!

I'm asking my installer to change for another system as this is absolutely bad behaviour of Victron asking some re-seller that has no idea about how it works to support installation.


Bye Victron, hope to never see you again!

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Alexandra avatar image Alexandra ♦ peter79 commented ·

@peter79

Your installer should have informed you your battery bank does not meet minimum requirents set out on the Vitcron ByD page, of your three phase system.

The unexpected behaviour of the soc of your bank is related to being undersized.

The behaviour you are experiencing is exactly what I see even on non BYD systems with underspec systems.

So at the end of the day the system is not working correctly because it is not set up correctly.

I personally would not have agreed to do your installation either based on that fact.

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peter79 avatar image peter79 Alexandra ♦ commented ·

Victrons have been mounted in MAR, until 25 JULY we waited for battery, only one cell arrived, ordered and paid are 3 cells. Installer said it is OK to start with one.

I have not read all Victron and/or BYD documents as I was expecting this to be job of distributor/installer - is this really my mistake?

The only request to installer was to have backed up whole house and that is all. He can chose what he want.

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mysik avatar image mysik peter79 commented ·

Hi, @peter79

1.1) Your DC load could be the Victron or could be something in the BYD battery (BMS or PDU). Best way will be to use clamp meter and measure you DC current flow between Multiplus and battery when it is in the "Discharge disabled" mode.

As per spec one Multiplus 48/5000 should draw not more than 30W ( zero load power - 30W; Zero load power in AES mode - 25W; Zero load power in Search mode -10W)

For Multiplus II the numbers are even lower (18W; 12W; 2W)

Also worth to note that some people complained about high power consumption from Multiplus with no AC loads in the past. The Victron replied that "standby load varies a lot per unit", so maybe yours are out of spec.

1.2) I agree and absolutely understand you. It can be quite frustrating when the system is not behaving as you would expect, but as always it is all in details/small prints, which not many people are aware of before installation. I solved this issue with the BMS which is not allowing to draw any power from the battery (basically it is disconnecting the battery from the load if it reached lower limit)

2) 300W sounds a lot for stand by power consumption, way too much. Did you measure it with the clamp meter?

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peter79 avatar image peter79 mysik commented ·

1.1 I have read the specs and I have nothing against this consumption, but when battery discharging is disabled this consumption should go from grid not from battery, reason is that the minimal SOC should be saved for outage situation. For this reason it is not possible to set this limit in battery as battery will disconnect at 10% SOC regardless if there is outage or not

1.2 I'm sure somewhere it is written in small letters, but if battery would be not discharged under SOC there will be no need to charge back to min SOC - note that the charging is with 4kW causing all 3 inverters to run fans at full speed, they are mounted in garage, but during the night in quiet house you can hear them anywhere in the house - this is seriously impacting quality of sleep and that is serious reason to dismount the Victrons

2. No I have 'measured' only by counting from the screenshots, quality of measure on screenshots was verified by calibrated meter used to create invoices in my country and the victrons are 'wrong' by +- 50W, in general 300W standby for 3x5kW online UPS would be good number, but Victrons are OFF-LINE UPS only

Currently the replacement solution seems to use GoodWe 10K (backup output can not be used) + 3x on-line UPS (most probably eaton). Installer already checking availability. Worst on this option is cost and fact that GoodWe battery can not be used for UPS (low current per phase on backup output).

Edit: Other reason to dismount Victrons is that their policy is by any failure disconnect the loads also on non failing units, this is exactly opposite to normal UPS that do everything to keep load running (on UPS failure bypass is used - load not protected, but runs until grid failure)

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Alexandra avatar image
Alexandra answered ·

@peter79

1. will be because you have battery life on. And because some BYDs get a SOC drift sometimes to correct it you would need to charge up fully and keep it there. Sometimes the BMU itself wont allow any more discharge to oreserve its bank (cell balancing maybe one or two cells are lower than others so further discharge could damage them)

1.1. yes they will stay there until solar charges them up, usually the system will go into passthrough until the solar is enough to cover loads and charge. (Also battery life related)

1.2. if you disable grid charger there is no way to charge from grid.

2. Some will be system consumption, some will be wiring and heat losses, battery inefficiency. If they are high then it is usually a set up issue or if you have no shunt or smart battery it is a calculation or assumption by the system so not always on the mark. But you have a BYD so likely on the mark.

3. UPS funtion, the battery is undersized so cant produce surge needed and that would most likely be the issue. And possibly undersized cabling.


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peter79 avatar image peter79 commented ·

@Alexandra, thank you for answer. Your thinking is very similar to my, but how would you explain the attached pictures (to original post)? Battery happily discharging when under minimal SOC (1.1), battery charging from grid (1.2)? It behaves exactly opposite as we both think it should.

Are the Victron units faulty?

I have minimal SOC 10 % and settings without battery life

Settings.jpg

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settings.jpg (61.6 KiB)
Alexandra avatar image Alexandra ♦ peter79 commented ·
What is set on the gx to monitor battery SOC?
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peter79 avatar image peter79 Alexandra ♦ commented ·

I found following:

Battery monitor: Automatic
Auto selected: BYD Premium LV battery

Is that the information you asked about? If not can you please advise me where/what to search?


Thank you

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Alexandra avatar image Alexandra ♦ peter79 commented ·
No thats fine. BYD is monitoring then
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Alexandra avatar image Alexandra ♦ peter79 commented ·
6% is at 51v (discharge)

8% is at 53.1v (charging)

10% is at 52.3v (charging)

All with similar loads.

The DC voltage varies quite a bit and not how I would expect it to behave as lithium is fairly linear. You have cells out balance badly. And possibly SOC drift.

They need a good charge and to be kept there for a while.

Either that or the multi is the battery monitor on the GX?

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peter79 avatar image peter79 Alexandra ♦ commented ·
It is solar system so the bateries are usually full during day. For example today they reached full at 10:00 and start discharging around 20:00, ~10 hours on full charge (is it sufficient?).

I do not have sufficient knowledge to comment on the voltages, what can I do to make the cells more happy?

Monitor seems to be the BYD (see my other comment)

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peter79 avatar image peter79 Alexandra ♦ commented ·

One more point in my mind, If there is minimal SOC set I can imagine voltage might influence it, but when there is set "NO CHARGING FROM GRID" how can the voltage influence it? My impression (?!) was that this config parameter is not voltage or battery related. It should (as per my knowledge) be settings of Multiplus and when charger on Multiplus is disabled it should not provide any charge regardless of battery voltage.

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Alexandra avatar image Alexandra ♦ peter79 commented ·

So to some degree SOC and voltage are not related, however there is a certain voltage the cells in the BYD need to be maintained above and below.

If cells in the bank are lower than other cells then the system will stop discharging earlier than your SOC set to prevent them from getting too low.

The BYD will then also ask the system to charge to sort out the lower cell issue. The entire time it is the BYD influencing the system charge and discharge.

If you get to 100% everyday and kept there for a few absorption cycles it should be enough. Check the temperature during charging of the battery pack.

The only way to make sure you dont get a charge from grid it to disable the internal charger in the multiplus.

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peter79 avatar image peter79 Alexandra ♦ commented ·

I have checked the cells difference and currently the min cell voltage is 3.32 and max is 3.34 (until I made screenshot it was 3.33). Any other system to compare if 0.02 (or 0.01) is too big or too small?


Current battery temperature is 27 and absolute maximum during charging was 35.

Edit: fixed typo in temperature

2022-08-02-21-07-01.png

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nickdb avatar image
nickdb answered ·

wrt to the UPS functionality, remember that if the grid browns out, the voltage will also drop on the AC out, until it hits the lower cutoff limit. This passing through of voltage is often what can cause sensitive devices to restart or reset. In a normal blackout scenario, provided loads are all on ac1 out, the cutover is fast enough to not cause issues. Ac2 out, of course, will be dropped.

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peter79 avatar image peter79 commented ·
This is partly mistake on my side as I got the impression that Victron is on-line UPS, but in reality is offline UPS. This is by design and can not be changed anyhow.

All loads are on AC1 out. Because I have UPS background, it seems to me that Victron uses 'Open circuit switch', but most blackout happens in 'closed circuit switch' ('short'), we have been testing UPS with 'short' as it is more difficult scenario for UPS to catch on.

From 27.7 we had 2 outages, one was correctly compensated by Victron UPS, second was not.

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nickdb avatar image nickdb ♦ peter79 commented ·

We live in a region with an extraordinarily bad grid, rolling blackouts are a constant feature over the last 2 plus years, with 2 to 3 outages a day at the worst.

Voltage fluctuations are common before and after an outage.

My personal system has logged just under 300 grid failures, out of that 1 reset sensitive devices (and I have a few).

My office has more sensitive gear and we have had no upsets.

So it does work, but you are at the mercy of grid quality on failure.



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peter79 avatar image peter79 nickdb ♦ commented ·

The inverters worked 5 days until the distributor (not installer) has broken the system. Now one inverter is refusing to start causing the other 2 also not start.

In that 5 days we had 2 outages and first of them was catched by Victrons, second not. Most sensitive electronics in house are remote switches (which reset usually first and configuration is very time consuming manual activity), door openers (very problematic element as it has no position limit switch, when someone not knowing there was outage uses the door opener it results in motor fire if he does not recognizes his mistake fast and does not turn off - again settings of one door opener is cca 15-20 min), clock (many around the house, usually quite fast to set, but I feel like monkey setting them each 2nd day :-) )

With this I have learned also one new topic and that is that Victrons does not have bypass switch, resulting in each failure causing loss of power - this is exactly opposite to my expectation and to UPS manufacturing standards.

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