HIgh voltage alarm - victron products

Henrik

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Hi!

I have 2 solar panels 2x230W, serial connected (2x24 v). Connected to a Victron MPPT SmartSolar 100/20.

The MPPT feeds an 8 cell LifePo4 battery (24 volts). The LifePo4 battery is controlled by a Daly BMS 8S

On the Battery negative side, I have a Victron SmartShunt installed. There is also a Victron Sinus Inverter connected.

According to the VRM portal I started getting High voltage alarms. It says over 30V going to the batteries. I measured the battery + - on the MPPT and I do get a bit over 30 voltages. Not sure why. The MPPT is set as a 24V charger. The config of the MPPT is according to the standard for LifePo4, giving charger voltage at 28.4. You can also see that one of the graphs jumps when this happens, while other graphs show normal. Still my DC tester also shows over 30V.

Temperature in the garage where all hardware is installed is around 15 degrees C (not too cold, not too hot)

How can I even get an output larger than set in the MPPT controller? It should be impossible, right?

Seems to be happening when battery gets close to 100%.

Appreciate all help I can get.

Faulty MPPT charger?

As mentioned earlier, I have no external charger connected. And not anything else that can "add" energy to this system

MPPT settings:

Max charge current: 20A
Battery voltage: 24V
Absoption voltage 28.4V
Float Voltage: 27V
Charger enabled: True (which is the charging function of the MPPT as I understand it)


Daly BMS 8S 24V settings:

Cell volt high protect: 3.65
Sum volt high protect: 29.0V
Chg overcurrent protect: 25A
DisChg overcurrent protect: 30A

Everything running latest fw available

Latest update: I started a small radiator (200W) and alarm went away. Still, why do I get over 30V from MPPT battery connection points when I measure?

1631721197873.png

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Henrik

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I also add picture of statistics showing that this more or less only happens when close to 100% SoC. But still, purpose of MPPT is to never go over max voltage charge is set to, which still is only 28.4V

1631724576981.png
 

rmaddy

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It's odd that the "Solar Charger Battery Voltage and Current" graphs never show it getting anywhere near 30V. So the SCC doesn't ever report such a high voltage. But I supposed that could be part of a faulty SCC.

You mention having a Victron Sinus inverter. What's a Sinus inverter?

Do you have any other charge source such as an inverter/charger or anything else?
 

RCinFLA

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Are you sure your BMS is not shutting down for cell overvoltage due to cells out of balance? When BMS shuts down it may take a moment for charge controller to react to sudden lightened battery charging load, momentarily going above charge voltage limit setting before it drops back down.

With charger on inverter side of BMS output and light enough load on inverter the inverter could keep operating supplied directly by charge controller.
 
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mikefitz

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I suggest lowering the absorption voltage to 28.0 volts and absorption period to 15 minutes . I suspect one of the cells is exceeding the limit in the BMS.

Mike
 
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Henrik

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Hi!

Good input. I added some comments

1. Victron inverter 24/375 (sinus is the more pure form of electricity, alike the electricity coming from wall outlets)

2. No other charge/power source anywhere adding anything. (Not counting the power of love)

3. I see no alarms from BMS. Alarms shown in VRM sometimes are active for several hours. Also note I measured the battery outlets of the MPPT charge controller. My instrument shows little more than 30V. That output should not be able to get affected by my BMS (I guess(?) )

4. Inverter has to be run via battery as no loads are connected directly to "load" port on the MPPT. All loads runs from the Inverter that takes energy from battery. Victron MPPT is really bad at handling inverters through "load" ports. I mean....really bad (buggy)

5. What will technically happen if one cell exceeds the BMS setting limit in relation to the set voltage from a MPPT controller? I don't understand how that would work

General: I still don't understand how a hardware after the MPPT controller can cause the controller itself to give a higher voltage than set in the MPPT settings. I thought that was the main job of the MPPT? I read in another forum that a guy lowered voltage in settings. I also think it would work. But to be honest, that workaround would make me disappointed of Victron as a brand, based on their recommended standard settings used wordwide.

Also, pretty interesting. Alarm went away after I added a load. When no alarms, the output ports from MPPT to battery is correct, when measuring.

I will keep a closer look of BMS alarms (I cannot se history right now).

But let's say BMS shuts it off and disables charging of the battery. It only does that because it is designed to do so (29V in settings), and the reason for doing it is that the MPPT gives too high voltage.

I would accept some alarms hitting a level and then going back pretty quickly, but that is not the case here. They are stuck for quite some time according to logs.

I will start with lowering absorption time to 15 mins

Also want to mention that the Smartshunt settings are:

High voltage alarm: 29V
High voltage reset alarm: 28.4V


One last thing: I mentioned earlier that I added 200W load and alarms went away. I always have a load of about 10W (Raspberry Pi running VRM) but the load is less than the 15W minimum that can be seen by the AC load reading in the system. A real flaw in the Victron logics if you ask me.

1631734609336.png
 

Henrik

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Seems main issue is all the different voltage readings from different involved hardware. Not sure how to correct that but as long as it looks like that, alarms can go off in all directions I assume.

I saw in another forum that a person had alike issues with voltage differences up to 0.2 due to a fuze with too high resistance. But here we are not talking about 0.2 v. More closer to a little more than 2V of difference in pictures.

Although, exactly now, I got a voltage difference of 0.2V between MPPT readings and SmartShunt reading. Seems that difference multiplies by 10 once the system is working with charging/loads during the day.

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RCinFLA

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The fact you say it only happen when battery gets near full charge is the most compelling info.

The BMS will shut down if any single cell exceeds 3.7v. This often happens when cells get out of balance, The overall charging voltage or absorb timeout has not been satisfied but one cell is fully charged and exceeds 3.7v. The BMS shuts down until high cell's bleed resistor pulls overvoltage cell back within reset limit (likely 3.5 to 3.6v). At this point the BMS will reactivate. Process may repeat all over again if cell rises above 3.7v again.

The next key piece of info is if overvoltage is just momentary or does it actually last for some time. This is not just reporting multiple times but actually measured to last for more then just a second or two. Charge controller does not expect a sudden removal of charging load current so it will likely overshoot for a moment if BMS opens path to batteries. Normal battery charging does not have a immediate step drop off in charge current so charge controllers are typically not fast for feedback control on charge voltage. It is concentrating on pushing current to batteries so a sudden load removal will cause it to overshoot in voltage. It should correct within a second or two.

The charge controller is in parallel with battery line going to inverter. Charge controller can power inverter if load on inverter does not exceed PV supplied current. The fact you were charging battery says the inverter load is less then available PV power.

Other things can cause voltage overshoot ringing. Long separated battery lines have series inductance that can cause over/undervoltage ringing with suddenly changing line current (inverter load surge current). This is hard on inverter input capacitors and in extreme cases can blow out inverter MOSFET's. Taping neg & pos battery cables together in parallel greatly reduces their series inductance.
 
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Henrik

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The fact you say it only happen when battery gets near full charge is the most compelling info.

The BMS will shut down if any single cell exceeds 3.7v. This often happens when cells get out of balance, The overall charging voltage or absorb timeout has not been satisfied but one cell is fully charged and exceeds 3.7v. The BMS shuts down until high cell's bleed resistor pulls overvoltage cell back within reset limit (likely 3.5 to 3.6v). At this point the BMS will reactivate. Process may repeat all over again if cell rises above 3.7v again.

The next key piece of info is if overvoltage is just momentary or does it actually last for some time. This is not just reporting multiple times but actually measured to last for more then just a second or two. Charge controller does not expect a sudden removal of charging load current so it will likely overshoot for a moment if BMS opens path to batteries. Normal battery charging does not have a immediate step drop off in charge current so charge controllers are typically not fast for feedback control on charge voltage. It is concentrating on pushing current to batteries so a sudden load removal will cause it to overshoot in voltage. It should correct within a second or two.

The charge controller is in parallel with battery line going to inverter. Charge controller can power inverter if load on inverter does not exceed PV supplied current. The fact you were charging battery says the inverter load is less then available PV power.

Other things can cause voltage overshoot ringing. Long separated battery lines have series inductance that can cause over/undervoltage ringing with suddenly changing line current (inverter load surge current). This is hard on inverter input capacitors and in extreme cases can blow out inverter MOSFET's. Taping neg & pos battery cables together in parallel greatly reduces their series inductance.

The time I measured was when the overvoltage had been there already for some time. Seems this can be seen for some while. Cabling in my case are very short in general. Between battery and shunt there is 1 dm and between shunt BMS, another dm. Between BMS and battery it is about 3 dm. Same length on positive side.

No issues today!!! Probably because the sun decided to bail out on my further tests...
 

RCinFLA

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If the overvoltage is there for long period it must be charge controller when it goes into absorb voltage limit. Maybe it is off in setting calibration such that if you set 28.4v it actually regulates above 30v. See if you can correct problem by lowering absorb voltage setting. Set it specifically to a lower level and measure with voltmeter to see if it regulating where you set it to.
 

Henrik

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Today while at work I got another alarm. When I came home alarm had already recovered. Although, in the BMS software I found a high voltage alarm. Not for a specific cell, but for the battery in total ("sum volt high level 2"). The BMS has high volt protect set at 29V.

I will work from home tomorrow and will be able to check alarms and do some measures when alarm comes again. Today the alarm came 30 min after the battery was fully charged.

All I changed since earlier was setting absorb time to 15 mins instead of 2 hr. I will run tests again and also try to lower the absorption voltage to 28. The alarm was a bit more than 2 hours this time.
 

Henrik

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Strange! People in these forums mentions that bulk and absorption is the same. But Victron does not seem to think so according to attached picture. In this picture it is clear that my alarm issue comes as soon as absorption is finished and goes back to bulk. Bulk does not seem to care much for the voltage setting. Then the alarm keeps going until the sun goes down :)

It seems we got closer to the main issue here. I'm guessing the setting "Re-bulk offset" setting in the SmartSolar MPPT at 0.2V gives me some issues here.

1632160407910.png
 

Henrik

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I checked my history for other alarms. Strangely I cannot see the absorption starting/stopping at all during those alarms. I can only see bulk.
 

Henrik

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Now I did some more tests as I got more alarms.

While alarm was active I measured voltage. It is about 30.4. While having alarm I lower the settings in the MPPT controller to 28 from 28.4. And yes, these 0.4 is seen with my voltage meter.

So I would have to lower MPPT settings to 26 or so in order to have 28.4. Seems like a faulty MPPT controller to me to be honest.

While having the alarms I also set Inverter to off to see if it had something to do with it. The power used from it was about 10W. It made no difference when turned off.

I also set MPPT battery charge settings to LifePo4 standard. It made no difference.

Currently I have these 3 alarms on my BMS also.

Sum volt high level 2
Cell volt high level 2
Diff volt level 2

My BMS says SumVolt currently is 30.0. My cutoff is 29
My BMS says these voltages per cell:

3.772
3.854
3.666.
3.823
3.804
3.809
3.746
3.550

I still wonder why Victron decided to try to fry my batteries almots on daily basis. I of course also wonder why the BMS lets it.
 

Short_Shot

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So the victron is actually ramping up to 30 volts it looks like from the one chart?

Sounds like a faulty unit. It shouldn't even really be reaching 29 tbh.

Your bms is also apparently faulty or setup wrong to be allowing the cells to get that high in the first place.
 

Henrik

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I then put some more load on it, about 250W. Still showing to high voltage from MPPT when I measure with voltage meter.

I then set MPPT charge voltage to 26. It now measures 26.5.

BMS cell voltages are now:

3.436
3.444
3.456
3.447
3.472
3.443
3.414

Not really sure about anything at the moment.
 

Henrik

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So the victron is actually ramping up to 30 volts it looks like from the one chart?

Sounds like a faulty unit. It shouldn't even really be reaching 29 tbh.

Your bms is also apparently faulty or setup wrong to be allowing the cells to get that high in the first place.
Yes, MPPT measure with voltage meter shows over 30V.

When I started using it I tried it out, setting the BMS to lower settings to see if it kicked in and it did. Not sure why it does not do that now. It would be another thing if it would read wrong, hence act wrong, but it seem to read correct but act wrong.

I will check the age of the MPPT to see how long warranty I got on it.

I might consider restarting it also but to be honest, that is not a good workaround. Would be there again after a while I believe.
 

Short_Shot

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28v should be more than sufficient. Charging up to 3.65v is excessive and there is very little extra capacity to be gained. Just a few ah.

Your cells will last much longer if they never exceed 3.5 volts as well.
 

Henrik

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Another question, Bulk and Absorption are considered the same. But why does this MPPT have 3 separate lamps then? One for bulk, absorption and float. When at bulk, most of the time voltage seem to be correct. Then when alarms comes, it generally did most of the charging needed. Could it be that it is a high voltage due to battery being full and that I at that time don't get any amps anyway? I guess high voltage with low amp still can overcharge battery
 

Henrik

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28v should be more than sufficient. Charging up to 3.65v is excessive and there is very little extra capacity to be gained. Just a few ah.

Your cells will last much longer if they never exceed 3.5 volts as well.
If I set mppt to 28 it still goes up to 30V :)
 
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