No load, not using - dropping voltage - CC off overnight

[arjuna34]

*No load - no usage - dropping voltage <22V - after sunset CC turns off*

Hi experts,

On setup below, having no active load (inverter off), minimal usage during the day, after sunset, always within 1-2 hours the charge controller turns off.

24V System
2x 460W panels in series
MPPT Epever 60A Charge controller
Inverter: 24V-230V, 1500W/3000W
8x LifePo Litheum 280A batteries in series.
BMS 4s lifepo4

Multimeter reading: 22.1V (now in the morning).

Typical day:
Mornings: CC come online, reading 3.2-3.5V total. I reset CC, typically it reads 22V.
Sunlight: runs up to 28V 100% SOC.
Daily usage: Often nothing at all: charging phone and laptop.
Sunset: in 1-2 hours (even with inverter turned off) CC shuts down.

The reason, and solution keeping batteries operational, can you help with your suggestions, and solution?
What should i check?

Let me know. Thank you.

 

[sirslayer]

Maybe your batteries are not balance?? Batteries that are out of balance tend to leach the potential difference from the other batteries..

 

[crossy]

BMS 4s lifepo4

This worries me slightly, typo or ...

 

[arjuna34]

This worries me slightly, typo or ...

Right, the BMS 8s lifepo4 I have. Thanks

 

[arjuna34]

Maybe your batteries are not balance?? Batteries that are out of balance tend to leach the potential difference from the other batteries..

Maybe.

Though, the BMS 8S should take care of the balancing.

My app shows the BMS regularly goes on and off, and balancing is sometimes on, sometimes off.

At the moment: Diff vol 0.016v. Though other times it can fluctuate up to 0.6v diff.

This helps to identify the cause of dropping voltage right after sunset?

 

[timselectric]

8x LifePo Litheum 280A batteries in series.

Hopefully you mean cells, instead of batteries.

BMS 4s lifepo4

And this is the wrong BMS.

 

[mikefitz]

At the moment: Diff vol 0.016v. Though other times it can fluctuate up to 0.6v diff

Seems the calls are out of balance, what are the cell voltages at the end of the day?
What battery charge current are you getting at midday?
How are you measuring SOC?

3.2-3.5V total. I reset CC, typically it reads 22V.

Are the 3.2 to 3.5 the cell Volts? This does not agree with 22 volts, even 8 cells at 3.0 volts is 24 volts total.

Sunset: in 1-2 hours (even with inverter turned off) CC shuts down.

What shuts down , the charge controller or the battery ?

Perhaps you could make things a little more clear, the charge controler shuts down what, the load outputs ?

Is perhaps the battery shutting down, are you getting high cell or low cell protection errors?

What BMS are you using?

 

[arjuna34]

Thank you for the inputs.

Screenshots today of the BMS app.

Observations:

11:11h* cloudy morning: 26.7V. 100% SOC

*BMS active balance on

19:44h after sunset: charging laptop -1.6A, 24.9V, 97% SOC

(19:45 Turn off inverter, no more load)

20:03h: 25.7V, diff volt 0.048V, 96% SOC
20:33h: 25.6V, diff volt 0.707V (!), 97% SOC
20:58h: 27.6V, diff volt 4.927V (!!!?), 96% SOC
21:04-21:15 charge controller has shut down.

Question;
1. What to make of these readings: diff volt 0.7-4.9V between 20:33-20:58?
2. What more data is insightful to track?
3. What resolutions could I try?
4. anything else to consider?

 

[arjuna34]

Seems the calls are out of balance, what are the cell voltages at the end of the day?
What battery charge current are you getting at midday?
How are you measuring SOC?
Are the 3.2 to 3.5 the cell Volts? This does not agree with 22 volts, even 8 cells at 3.0 volts is 24 volts total.
What shuts down , the charge controller or the battery ?

Perhaps you could make things a little more clear, the charge controler shuts down what, the load outputs ?

Is perhaps the battery shutting down, are you getting high cell or low cell protection errors?

What BMS are you using?

what are the cell voltages at the end of the day?
Today 24.9-25.7V. see screenshots. At 20:00-20:30 the diff volt read 0.7V up to 4.9V!

Are the 3.2 to 3.5 the cell Volts?
This is typically what the mppt display reads coming online when the first sun hits the

What shuts down , the charge controller or the battery ?
Charge controller shuts down. And thr inverter will stop giving power.
panels.

What BMS are you using?
LifePo 8s 24V 100A:

https://www.amazon.es/-/pt/gp/aw/d/B0B2NX5WBL?psc=1&ref=ppx_pop_mob_b_asin_title

 

[Checkthisout]

Thank you for the inputs.

Screenshots today of the BMS app.

Observations:

11:11h* cloudy morning: 26.7V. 100% SOC

*BMS active balance on

19:44h after sunset: charging laptop -1.6A, 24.9V, 97% SOC

(19:45 Turn off inverter, no more load)

20:03h: 25.7V, diff volt 0.048V, 96% SOC
20:33h: 25.6V, diff volt 0.707V (!), 97% SOC
20:58h: 27.6V, diff volt 4.927V (!!!?), 96% SOC
21:04-21:15 charge controller has shut down.

Question;
1. What to make of these readings: diff volt 0.7-4.9V between 20:33-20:58?
2. What more data is insightful to track?
3. What resolutions could I try?
4. anything else to consider?

Cells are grossly out of balance.

Balance the cells, charge fully with a power source and reset soc.

 

[Horsefly]

Another Daly BMS horror story...

Although others may be right that your cells are out of balance, the sequence of screen shots from your BMS would seem to indicate something has gone insane inside the BMS. To have one cell jump to 5V and another drop to near 0V a few minutes after they were both closer to normal is not likely to be accurate.

 

[Checkthisout]

Another Daly BMS horror story...

Although others may be right that your cells are out of balance, the sequence of screen shots from your BMS would seem to indicate something has gone insane inside the BMS. To have one cell jump to 5V and another drop to near 0V a few minutes after they were both closer to normal is not likely to be accurate.

Are Daly that bad?

Mine has been ok so far.

But yeah, look at this screenshot from his earlier post. Wonder what kind of cells he's using, his build etc? Is everything torqued??

 

[mikefitz]

Charge controller shuts down

It may shut down but the cause is the battery shutting down, see screen capture at 20.58. Both the charge and discharge fets are off.
Cell volts are totally unacceptable at this point as recorded by the BMS, measure the actual cell volts with a meter.

What is occurring at 20.58 that can effect the battery? you state no load or charge at this time.

Whilst the cells may be unbalanced this is not causing shutdown without other issues

Your screen capture,
Time current volt delta fet
19.44 - 1.6A .442 on
20.03 0 .048 on
20.34 0 .707 on
20.58 0 4.92 off
Next day
11.11 + 2.8 .210 on

I guess a bad BMS. Perhaps a faulty cell. Faulty connection.

Check all balance lead and cell interconnection. Check cell volts with a meter, compare to BMS cell readings

 

[Checkthisout]

It may shut down but the cause is the battery shutting down, see screen capture at 20.58. Both the charge and discharge fets are off.
Cell volts are totally unacceptable at this point as recorded by the BMS, measure the actual cell volts with a meter.

What is occurring at 20.58 that can effect the battery? you state no load or charge at this time.

Whilst the cells may be unbalanced this is not causing shutdown without other issues

Your screen capture,
Time current volt delta fet
19.44 - 1.6A .442 on
20.03 0 .048 on
20.34 0 .707 on
20.58 0 4.92 off
Next day
11.11 + 2.8 .210 on

I guess a bad BMS. Perhaps a faulty cell.

Home-built battery. Possible bad connection too.

 

[crossy]

This is starting to sound like a combination of issues.

Check and check again the BMS sense wire connections are good, everything cleaned up, no iffy joints etc. etc.

You really need to top-balance your cells. Are the cells new, known good, from a reputable supplier??

Could be a bad BMS.

Some photos of the battery pack would help spot potential problems.

EDIT The feeble balance current that the Daly BMS provides will take literally weeks to sort the issue (if it even can), if you do have mismatched/worn cells then a proper flying-capacitor active balancer is order of the day.

 

[arjuna34]

Good morning everyone,

This morning the battery’s behaviour showed like this:

9:17h Charge controller comes online: display 0.0V.
9:18h I reset the charge controller: slowly the voltage display goes up to 27.6

9:17h Diff Volt 4.690V! Cell 3 at 0.308V, Cell 4 at 5.0V!
9:19h multimeter reading: Fluctuating 1.8V-3.2V on each cell, in 1 to 2 minutes each cell stabilises at 3.2V

9:22h: Diff Volt: 0.011V

9:23h I start charging my phone and battery pack: -1.6A

9:38h I try connecting the fridge (125W/5.2A). The invertor 24V—>220V (1500/3000W) starts beeping. The Diff Volt reads 0.586V

1. What to make of this behaviour overnight and coming online: cell 3 at 0.308V and cell 4 at 5.0V?
2. In 2-3 minutes the battery seems balanced. For the BMS functionality what does this mean?
3. Connecting the fridge (125W/5.2A) why the inverter doesn’t seem to take it?
4. What further checks, and solutions can you suggest?

 

[arjuna34]

And for the battery - mppt - inverter connections it is connected like this.

Any alterations, ensuring fault proof connections you can suggest?

 

[mikefitz]

fault proof connections you can suggest?

It's hard to believe that voltages meter readings on a cell can fluctuate 1.8 to 3.2 volts. Readings of 5.0 volts from the BMS on 3 cells suggests a wiring or BMS fault.
The general setup indicates a 'casual' approach. No over current protection, ( fuses), strange tape on cable connections, no fixture to prevent cell movement, ( I guess the system is in a R V. I see a ratchet strap as an attempt), no insulation between cells, no buss bars.

Although improvements need to be made for safety and reliability, the less than ideal setup does not explain the strange cell voltages.

Suggestions.
Check your multimeter, is the internal batery OK, does it provide a stable reading on a voltage source, say vehicle battery.

Dusconnect the sence wires connector at the BMS.
Examine each cell terminal whilst carefully taking the 24 volt battery apart, examine each cell terminal for corrosion, clean the buss bars.

Test the voltage of each cell with a meter, identify each cell and note the voltage.

Report these readings here and await suggestions as how to proceed.

Do you have AC power and other chargers apart from the Epever?

 

[Checkthisout]

Give each balance lead a healthy tug at the crimps on each ring connector and see if they pull out.

Check all the nuts holding the bus bars down to make sure they are torqued.

It looks like one of the balance leads is charred but it may be just be dark.

I can see a few possible points of high resistance in the battery lead crimps and that splice there.

Going to assume poor connections are the issue. Resolution is to remove cells, top balance and just kinda redo the whole thing with new crimps/connectors etc.

I suggest getting someone to give you a hand.