Inverter over voltage and shutdown

[Borneoboy]

My 3kw generic 24 volt inverter shuts off when the SCC approaches full charge on the batteries. Usually the shut off only lasts 20 to 30 seconds and the inverter comes on again.
This is a continual cycle until a big load is applied or half the solar panels are turned off manually, which is my current "fix".
Typically happens after noon when all solar panels are in full sun.
Voltages seen at this time are 29+ and even as high as 33 for a moment or two.

 

[DJSmiley]

Which batteries? 33V is very high and should be only occasional when you have a lead-acid and the charger is doing equalization (Which it shouldn't do very often)

in all other cases it should be lower. With LFP it can be as high as 29.2V but it's usually recommend to have an absorbtion of 28-28.4V max.

What is your setup? First guess would be an issue with the charger (not set properly for the used chemistry) or failing charger.

 

[Borneoboy]

LIPO 100Ahr batteries. The controllers are PowMr, not the most expensive, but good value and performance.i have tried "throttling down" to 13.6 (27.2) volts max to stop the overvoltage, but it still happens when the battery/ies get full and the MPPT cycles between bulk charging and absorb at 13.6 (27.2) volts. At this point the MPPT dances about madly with the PV input going up to 60v and down to 40 or so and the current coming right bavk to zero or just a few amps.
That MPPT (I have two) is normally giving 60 volts and about 10 amps from two 250 watt solar panels. It may be faulty, but works well otherwise.

 

[Supervstech]

LIPO 100Ahr batteries. The controllers are PowMr, not the most expensive, but good value and performance.i have tried "throttling down" to 13.6 (27.2) volts max to stop the overvoltage, but it still happens when the battery/ies get full and the MPPT cycles between bulk charging and absorb at 13.6 (27.2) volts. At this point the MPPT dances about madly with the PV input going up to 60v and down to 40 or so and the current coming right bavk to zero or just a few amps.
That MPPT (I have two) is normally giving 60 volts and about 10 amps from two 250 watt solar panels. It may be faulty, but works well otherwise.

What LIPO batteries? Those blue ones from eBay? For some reason, they limit charge to 13.7V max. If you have the settings set for a 13.6 (27.2 paralleled) max output, and you are getting 33V, the controller is at fault, or your BMS is dropping out lower. Try 13.4V

 

[Borneoboy]

Yes, those cheap blue ones from Littokala/Varicore/EBay.
I'll try a lower setting, but afraid I won't get anywhere near full charge (27.2)

 

[Borneoboy]

Also it's only momentary high voltage, then fluctuating wildly...

 

[Supervstech]

Also it's only momentary high voltage, then fluctuating wildly...

Yeah, it is the result of the constant current mode on the charger hitting the charge disconnect threshold of the bms…

 

[DJSmiley]

In this situation its a 24V system so double any values by 2.

Anyway: I highly would recommend getting a decent controller and configure it properly.

The setup you now have has too many disadvantages to make it reliable
- Cells from one of the known sellers of crap and mixed quality
- Charger from one of the known overrated/not performing brands..

so basicly 2 things which will eventually cause major issues. Replacing the cells is going to be an investment (but I highly recommend getting proper cells next time, and not lillikola/aliexpress junk), but a proper MPPT will probably be sufficient for now.

The BMS is now probably disconnecting the charge, voltage spikes up, bms reconnect, voltage drops and that keeps repeating.
Get yourself a good controller like an Epever (or Victron if you want to spend money on high quality stuff), configure it properly.

While those cells aren't the best, it probably will work fine.

 

[Borneoboy]

And is there any easy solution to stop it happening?
I'll try lower voltage cutoffs on the SCC first...

 

[Borneoboy]

Mr D J Smiley
Send me a couple of thousand dollars and I will buy those things you recommend...
Despite the "Avatar" I am actually a 77 yesr old pensioner living on $1000 a month !!

 

[DJSmiley]

I wasn't suggesting replacing the cells. Although that would be better, the prices involved don't make sense and when properly charged those Lillekola ones will probably work also (maybe not at the rated capacity but probably still be sufficient).

Replacing only the charge controller is a much more affordable option and that was what I was recommending. That is not too expensive and will be sufficent for now (and to me is one of the more important parts - having underperforming cells (lower capacity) is something you can live with)

 

[Borneoboy]

Despite the low quality components, I get 24/7 free electric supply and this is the only problem I currently have.

 

[Borneoboy]

I have also had problems with the cells (of course !) and am currently in process of replacing three due to bloating, over high voltage and runaway charging...
The BMS saga is a whole other story and I have tried JBL, Heyo and various Daly ones - none very impressive... frankly the cells seem to behave better when left to themselves !!
I think we have a long way to go in the evolution of solar power, at least the small scale affordable systems. And some of the horror stories I read on this forum (and others) seem to bear witness to this.

 

[Borneoboy]

Yeah, it is the result of the constant current mode on the charger hitting the charge disconnect threshold of the bms…

It seems to be when the SCC changes from Bulk to Absorbtion mode (and back again). Because of the single cells (7 & 8) always reaching 3.65 volts way before any others, this happens a lot.
I agree they are very "cheap & nasty" SCCs (PowMr. !) but there must be some solution ??

 

[buyone]

Yes, those cheap blue ones from Littokala/Varicore/EBay.
I'll try a lower setting, but afraid I won't get anywhere near full charge (27.2)

I've got those and they aren't LiPo, they are LiFePO4. Completely different.

 

[flopsi24]

Hello together,
i have the same issue 2 Years later
My Setup is:
PowMr HVM 10.2m (10200w; 2MPPT; Offgrid)
PowMr LIO48200-15S (~10kwh; 5kw)
the failure is like you descripe ist, when the PV Strings are in the full sun an the Battery is at the end of Bulk charging (at my Setup 50.5V), then the Outputpower with a Heatpump (~2,5kw) is going to wabbling.
It seems that die Outputvoltage is the problem.
The Voltage wabbling from 205V to 235V.
The Battery is wabbling with the Current from -30A (discharge) to 20A (charge).
I interrupt these wabbling with shutdown one pv string, disconnect the load, or put a bigger load to the system..

Is there any Solution for these Problem?

 

[Supervstech]

Hello together,
i have the same issue 2 Years later
My Setup is:
PowMr HVM 10.2m (10200w; 2MPPT; Offgrid)
PowMr LIO48200-15S (~10kwh; 5kw)
the failure is like you descripe ist, when the PV Strings are in the full sun an the Battery is at the end of Bulk charging (at my Setup 50.5V), then the Outputpower with a Heatpump (~2,5kw) is going to wabbling.
It seems that die Outputvoltage is the problem.
The Voltage wabbling from 205V to 235V.
The Battery is wabbling with the Current from -30A (discharge) to 20A (charge).
I interrupt these wabbling with shutdown one pv string, disconnect the load, or put a bigger load to the system..

Is there any Solution for these Problem?

I have read your question several times, i dont quite understand what is wrong.

 

[flopsi24]

My problem is the fluctuating output voltage, which causes the output power to fluctuate. The battery constantly fluctuates from +20A to -20A every 1-3 seconds.
The Problem occurs when the Solarpower is high and die Battery becomes full charged (floating Voltage)

 

[Supervstech]

What kind of batteries are you using?
50.5 is unusual.
What are the charge parameters?

 

[flopsi24]

The Batterys have nominal Voltage of 48V (15 cells), i want to charge only to ~80% for longer durability.

Bulk Voltage Point 51.0V and Floating Voltage 50.5V.