HELP! Charge/Draw Equal from PV, and Inverter/Charger on Shore Power

[lance]

Utterly mystified. Admittedly, I don't know a lot about what I'm doing here but, I built this system with tons of help from folks on this board, and it has been humming for the first several months it has been online. I can't say when this started but, it came to my attention about a month ago.

The system is 24v, 8S Eve 280 LiFePO4 Cells, 640w PV (4panels, 2s/2p), Victron MPPT and Inverter/Charger.

Somehow there is a draw being created that is equal to the input, whether from PV or inverter/charger.

This is with the PV breaker in the on position, and full sun.


This is with the PV breaker off.

I did not capture it with screen shots but, the exact same phenomenon happens with PV off, and inverter/charger on shore power in the charge position.

And, this is a day of PV charging/discharging:



There is a Batrium BMS and it mirrors what the GX is showing.

One final addition to the mystery is this that I captured at the end of the day yesterday. The batteries actually gained a couple of percentage points of charge.



There is an actual negative DC draw flowing into the batteries somehow.


And, lastly FWIW this is the system right now in full sun. Batteries are discharging:




Does anyone have any clues on this? Point me a direction to search for an answer?

All help immensely appreciated!

 

[MisterSandals]

Does anyone have any clues on this? Point me a direction to search for an answer?

This is another thread where someone has some unexplained Victron SCC behavior - it started when he upgraded firmware a couple days ago. Still have not pinned it down to anything. Just gathering clues.

You mentioned that this started a while ago. Do you recall if there was a firmware update around that time?

Also, are you able to confirm or deny the reported current flows with a meter? Especially the DC load that is reported.

Happen to have a pic of your setup or a diagram of how you have this wired. When envisioning how and where you could measure this, it became clear that this could be setup a number of ways.

 

[lance]

You mentioned that this started a while ago. Do you recall if there was a firmware update around that time?

No firmware updates have been done. Exactly how long it has been going on, I can't say but, I noticed it like 3ish weeks ago, and have just been monitoring it mostly. At first I thought it was PV only, and possibly a bad panel. Experimented with covering one pair while in broad daylight, and then the other pair, and all seemed the same.... just cut in half. But, then when I introduced shore power and the charger and saw the same phenomenon happening with the PV breaker off, I knew it wasn't panels.

Also, are you able to confirm or deny the reported current flows with a meter? Especially the DC load that is reported.

I'm afraid I have to plead ignorance here. I do own a multimeter but, barely know how to use it. I'm not sure where I could pick up a reading from.

Happen to have a pic of your setup or a diagram of how you have this wired. When envisioning how and where you could measure this, it became clear that this could be setup a number of ways.

This should get you to an album with pics of set up and diagram created to build it.

temp DIY Solar Forum

4 new items added to shared album

photos.app.goo.gl

NOW THOUGH:

The mystery deepens. I left to run some errands, and checked this while out only to find the batteries fully charged and the BMS having cut charging due to batteries hitting critical.



Still the dynamic remains the same with the DC draw essentially the same as the PV input but, somehow the batteries suddenly charged.


Now, this part is a little embarrassing: I completed this system back in April of this year. I was deeply immersed in it, and knew my way around things pretty well even if I didn't fully understand what I was doing. Now, 8 months later I'm having to relearn how to navigate, and cannot for the life of me find my way back to the settings for the SCC or the Inverter/Charger (both Victron) ugh! I remember there's a "secret" code one has to enter to gain access but, I can't find where. lol.... funny not funny.


On a separate note but, relevant to this: I wonder if there's anyone local to the SF Bay area that really knows what they're doing and might be open to being hired to review my settings/set-up, and just in general get things where they should be and perhaps give me some hands on education as well. Perhaps I'll start another thread with this search but, let me try here first.

 

[MisterSandals]

the BMS having cut charging due to batteries hitting critical.

Wow, battery is at 29.06V. That is mighty high to be charging LiFePO4 cells.
Is there a reason you are charging your cells that high (3.6325Vpc as pictured)? The cells are fully charged at 3.5Vpc and 99% at 3.45Vpc. While that is within the cell limits, its probably most concerning that you may be abusing your system when the BMS cuts battery power, possibly every time you get to full charge. This is REALLY hard on most BMSs and the SCC can't be very pleased with it either (most SCCs warn about lack of connected battery, especially when solar charging).

This is unlikely to be your reported issue, it just caught my eye and thought i would share my thoughts on it.

This should get you to an album with pics of set up and diagram created to build it.

Wow, somebody has some nice fabrication skills and attention to detail. Well done and thanks for sharing!

I remember there's a "secret" code one has to enter to gain access

Its either all 0's (6 i think, maybe 4). Failing that try everybody's favorite 1,2,3,4,5,6 (but keep it a secret).

I wonder if there's anyone local to the SF Bay area

Sending PM

 

[chrisski]

! I remember there's a "secret" code one has to enter to gain access but, I can't find where. lol.... funny not funny

You can reset the Pin on the Victron app by clicking the three dots on the right side.

You will be asked the device serial # which for my device was hidden underneath on the name plate on the back.

I needed to remove the SCC to read it and then install after I wrote the # down.

 

[lance]

Wow, battery is at 29.06V.

This is one of those places where I just need some help figuring it out. I have the "Cell Hi Cutout" on the BMS set to 3.55, and I don't remember where it is set on the SCC (still need to follow your directions above and find my way back to those settings I used to know my way to.) but, my memory is it is basically set to the same max. And still: I've seen it run this high a few times and just not known what else to do. I really do NOT want to be hard on those cells, or the SCC or BMS.

EDIT: The above BMS settings were from the "Charging" tab.... I just wandered to the "Critical" tab and found the Hi Cell Volt set to 3.75. I suspect this is the problem and am changing it to 3.5

Wow, somebody has some nice fabrication skills and attention to detail. Well done and thanks for sharing!

<blush!> Thanks! That was about two years of design/research/build but, I'm pretty proud of it, and getting that kind of feedback from someone who knows what they're doing is particularly satisfying.

I'm going to try finding my way back to the Victron settings now....

 

[lance]

Mystery Solved! Many thanks to @MisterSandals for his help on this...

When I built my system the layout was such that the shunt needed to be mounted reversed but, the software allowed for this by providing a reversed shunt option. When I first started the system that box was checked and everything flowed normally. At some unknown (and unknowable!) point, that box became unchecked. Thus the perfectly equal flow of power in and out of the PV system and batteries. Doh.

If you're running a Batrium BMS and shunt, keep an eye out for this.

 

[sunshine_eggo]

Sorry I missed this. I have both Victron and Batrium and experienced this early on.

About this:

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Hello all I have an Off-Grid inverter growatt spf5000 ES and it is connected to 4 655W panels without batteries so far, its idle consumption from the utility is arouns 2 amps, it is making my energy meter spin like crazy, this system was supposed to save money, now it is costing me money, is...

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Are you saying your inverter pulls 17-20W when it is in the off position?

Did you confirm this with a clamp DC ammeter on the feed wire to the inverter?

Did you exclude the Batrium, MPPT and GX draw as well?

If you're basing this on the "DC Power" value, the DC Power value is notoriously inaccurate. It's literally just a trash heap where any unaccounted for current AND ERROR lands.