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Victron smart mppt 100/20 goes up and down like a Yoyo and crashes output to zero

Blue-Flower

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Jun 28, 2021
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Location
The Netherlands
My setup:

1 solar panel Wattstunde WS200SB (200W, Umpp 19.8V, Impp 10.1A).

Attached to a smart solar MPPT 100/20 with the latest firmware 1.56. Victron Connect thinks it is a 48V version as well as my Raspberry Pi. The label on the device tells otherwise (ie no 48V written on it).(Sidenote: is there a physical difference between the two MPPT models? Or are they the same?)

Four 75 Ah LiFePO4 in series with an overkill like BMS. (Home made pack)

Main problem is that the mppt crashes its output to zero and starts up again. see the attached pictures. I have no clue why. I checked the BMS. No problems with it. It does not trip any error coditions.


I want this to be resolved. MPPT crashing all the time to zero output is not good.

What is going on? Is this the same bug that ought to be resolved in this firmware revision?

Is my MPTT broken and need to be replaced?

Or is it a problem that there is 1 solar panel attached with an output of only 5V above the battery? Do you have the same problem with 1 panel?



Any help is appreciated.
 

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Can you post your battery charge profile settings?

What are your BMS HVD settings? The controller might be tripping that. That would cause abrupt drop from mppt.
 
What I have done is the following:



Battery voltage: 12V (LiFePO4)

Max charge current 20A (I use a smart MPPT 100/20). I could set a bit lower.



Expert mode on



Charge voltages:

Absorption voltage set to 14.10 Volts. (that is 3.525V per cell and is a bit on the high side 14.00 would be better)

Float at 13.70V (we do not need to float these Litium Iron Phosphate batteries)

Equ voltage greyed out



Bulk:

Re-bulk offset 0.20V (is maybe a bit too low - just testing for the moment)



Absorption:

Duration 5 minutes (could be lower - just testing it while monitoring each cell in the BMS)

Tail current: disabled

equalization stop mode: fixed time

Eq duration: 0 minutes



Voltage compensation:

Temperature compensation disabled



The BMS controller is a bit more complex but I use my cells between max 3.60V and 3.00 V. Which relates to the steep inflection points in the IU curve and the state of charge (SOC) is then somewhere between 95% and 5%.

I use an Overkill BMS also known as LLT power or JBD type bms.

4S LiFePO4/120A bms with bluetooth. I have it for only one week and it works with Android and my iPad. I still have to tests it with an uart.



Base parameters:

Cell number: 4

Nominal capacity: 75 Ah

Galvanometer resistance: 0.20 milliOhm



Protection params:

Overvoltage: 3.60 Volts (V from now on)

Overvoltage release 3.45V

Overvoltage release delay 2.0 seconds (s from now on)

Undervoltage: 3.00V

Undervoltage release 3.25V

Undervoltage release delay 2s

Pack undervoltage 12.00V

Pack undervoltage release 13.00 V

Pack undervoltage release delay 2s.

Charging over temperature: 50 degrees Celcius (C from now on)

Charging over temp release 40C.

Charging over temp delay: 2s.

Charging under temp 5C

Charging under temp release 7C

Chargeing under temp delay 2s

Discharge over temperature: 50C

Discharge over temp release: 45C

Discharge over temp release delay 2s

Discharge under temperature -10C

Discharge under temp release 0C

Discharge under temp delay 2s

Charge over current 40 Ampere (A from now on)

Charge overcurrent release 32A

Charge overcurrent release delay 10s

Discharge overcurrent 60A

Discharge overcurrent release 32A

Discharge overcurrent delay 10s

Balance turn-on voltage: 3.20V

Balance precision 0.001V



Hardware protection:

hardware overcurrent protection 67A @ 160 milliseconds

hardware short circuit protection 89A@ 70 microseconds

short-circuit protection release delay 32s

Hardware overvoltage protection 3.70V

Hardware overvoltage protection delay 8s

hardware undervoltage protection 2.70V

Hardware undervoltage delay 16s
 
I also watched the bms during the charging. I diod not see anything out of the ordinary except for the current going up and back to zero.
I do not think that the bms is at fault. I could be mistaken though if the display on my Android phone lags a bit in time and does not show any tripping.
 
Victron settings
 

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Those settings look fine. Are you sure the batteries are not full? If they are fully charged, PV string voltage will go up, and power will go down. I think that's the issue. Add a load to the battery (a large load) and see if that solves it. I think the voltage of the battery is settling and the mppt is kicking on and off at the top.
 
Battery was not full.

I still have a hunch that it relates to using only 1 panel with an output voltage that is slightly higher than the battery. It is within spec of Victron, but I'm not sure if they really specify it correctly: PV must be 5V higher than battery. After the MPPT has started, this requirement drops to 1V above battery.
I do not have 2 panels or a higher voltage output panel.
I like to know if this is really the case. If so, I can go back to the seller of the panel and swap it for another solution.
 
Last edited:
Welp I give up. I hope someone can figure this one out.

Also be sure to check every connection and circuit breaker in your system.
 
What are your thoughts about the edited post? You just posted a message that you have no clue while I was editing the previous post. It crossed each other.
 
A screenshot of Victron Connect when it goes to 0 amps would help (e.g. it may display why it's not charging).

Based on your graphs, however, your solar input voltage goes to 0. Do you have an auto-reset circuit breaker between the panel and the SCC? Sort of seems like there's a connection or breaker problem between the panel and the SCC (or possibly a bad panel).
 
The MPPT screenshots shown in the first post shows that the output of the MPPT goes to zero. No errors or warnings were shown.
The solar output to the input of the MPPT should never go to zero. I'm not sure if the resolution of the graphs are good enough. I browsed through the stack of screenshots and attached a new one in this post. In the first post, there is a graph which did show the output of the PV going down to zero. I think it is an artifact or a glitch of the software. It is not very clear either. I never saw it again.
As you can see, I use only mechanical current protections. They never tripped.
 

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Last edited:
That's a smart solar mppt image.
Not the main overview page of VictronConnect.

I hope to capture an image tomorrow since the error lasts for only a few seconds.
 
Well, I swapped the solar panel for a different one. One that has a higher volatge output.
It is cloudy today and unfortunately no tests. Bummer.
 
I returned the solar panel and got one with a higher voltage: Wattstunde type WS120SF-HV.
Since then the problems were solved.

Apparantly, the Victron smart mppt 100/20 needs a higher input voltage panel to charge a 14V LiFePO4 system.
 
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