Victron Multiplus II keeps shutting off when SOK 48V Batteries at 50v and 85% soc.

[SkepticalTiger]

I have an issue with my Multiplus II saying Low Battery and shutting off when my 2 SOK 48V Batteries read 50v at 85% SOC and once it's at this voltage and SOC the inverter refuses to turn on unless I switch to shore power. These were purchased directly from Current Connected so the Multiplus II was programmed by them along with a Bluetooth adapter and MK3 USB interface. I bought a Smart Shunt separately for monitoring SOC. I have been trying to get help from Current Connected for the last few weeks but one of their reps seems to never respond unless I send multiple follow-up emails. The RJ45 cables that do connect my two SOK batteries were not purchased from Current Connected.

I am waiting for a specific cable to connect from my SOK batteries to the Inverter, but am not sure if that's just for GX devices. Typically I will have the battery pack running laptops and other devices which eat up about 5% of my SOC per week. I do notice the inverter will turn off during weekends if I don't use my devices for longer than about 48 hours. I was expecting to recharge my batteries to full 50% SOC since power outages in my area occur at random and 50% gives me about one week of power needs. Below are my current settings, but what can I change so my inverter stops shutting off at 50v and 85% SOC?

 

[sunshine_eggo]

50V is NOT 85% unless you're under a VERY heavy load.

Your SoC value is not accurate at all. The shunts require regular sync at 100% to maintain accuracy. Improper configuration will also reduce accuracy, sometimes wildly.

Why is virtual switch enabled? You have it configured to enable multifunction aux relay when voltage drops below 50 (DC low input alarm). Pretty sure this is why you're shutting down:



Recommend you change the pre-alarm to 48.5V and the recovery voltage to 49V to see if this changes the behavior. I'm not familiar with the function of that relay, but it's too coincidental that it's set to open at 50V, and the shutdowns are happening at 50V.

Generally speaking, you are using more power than you are replenishing taking your battery to low states of charge.

Also worth noting that if your battery is interfaced with your GX device, some settings are overridden by the BMS... the charger voltages in particular.

@HighTechLab can likely shed some light on this.

 

[HighTechLab]

I am heading home from lunch and will review the email thread with our tech and this info once I get back to my desk

 

[sunshine_eggo]

I am heading home from lunch and will review the email thread with our tech and this info once I get back to my desk

On a Sunday!!!! BOOM!

 

[Checkthisout]

Curious what the relay is driving that's making it shut down the inverter?

 

[sunshine_eggo]

Curious what the relay is driving that's making it shut down the inverter?

That's what has me confused. I've only used VS to toggle ignore AC input.

 

[740GLE]

You have a victron smart shunt and the MPII dongle so that they are connected in a virtual network?

Can you post the settings of the smart shunt?

I take it the values of 85% SOc is coming from the smart shunt, not the BMS readings?

 

[SkepticalTiger]

50V is NOT 85% unless you're under a VERY heavy load.

Your SoC value is not accurate at all. The shunts require regular sync at 100% to maintain accuracy. Improper configuration will also reduce accuracy, sometimes wildly.

Why is virtual switch enabled? You have it configured to enable multifunction aux relay when voltage drops below 50 (DC low input alarm). Pretty sure this is why you're shutting down:

Recommend you change the pre-alarm to 48.5V and the recovery voltage to 49V to see if this changes the behavior. I'm not familiar with the function of that relay, but it's too coincidental that it's set to open at 50V, and the shutdowns are happening at 50V.

Generally speaking, you are using more power than you are replenishing taking your battery to low states of charge.

Also worth noting that if your battery is interfaced with your GX device, some settings are overridden by the BMS... the charger voltages in particular.

@HighTechLab can likely shed some light on this.

The SOC value was coming from the BMS while the smart shunt pegged me around 70% I think. I synced it at 100% or float charge but have had to keep syncing it again each time the inverter shuts off since there's now low voltage warning.

I think I enabled virtual switch a while back. I was trying to setup something where shore power was on, but would only charge the battery when it got to a low enough voltage, but I ever quite got it to work properly.

I'll change those settings once HighTechLab responds in a bit, but it seems like aux relay enabled and pre-alarm are what's causing my issue thus far. I don't have any GX device yet.

 

[HighTechLab]

BMS communication requires a Cerbo-GX and will not fix this issue.

I am 95% sure what is going on here is the SOC has drifted (pretty far) out of calibration. Whether you are using a smartshunt or the SOC tracking on the batteries, the system will only properly recalibrate the meter 100% when they batteries get a full recharge. So, to start with, recharge to 57.6v (absorption).

From there, run some normal loads and see when the batteries are shutting down.

50V is down in the last 10% or so on these packs, so no matter what is causing the shutdown the batteries are empty and the SOC is wrong. I generally recommend all customers fully recharge to 57.6v once per week otherwise the SOC readings can mislead you. We can turn off VS but it's like turning off the A/C in the car because you are out of gas - it's not fixing the bigger issue here.

One other thing I need to address - I found this email went unanswered since 12/6 in one of my newer tech's inbox and I'm pretty sure it's because she needed to discuss it with our tech support manager for some help. I will have a meeting with both of them tomorrow - done means done and it should have not gone this long unresolved. So, thank you guys for bringing this to my attention so quickly to keep my attention on a potential bigger issue at hand.

 

[SkepticalTiger]

You have a victron smart shunt and the MPII dongle so that they are connected in a virtual network?

Can you post the settings of the smart shunt?

I take it the values of 85% SOc is coming from the smart shunt, not the BMS readings?

BMS was what gave me that reading. Here are my smart shunt settings, the battery % isn't synced at the moment.

https://imgur.com/a/OFM7kLO

 

[HighTechLab]

BMS was what gave me that reading. Here are my smart shunt settings, the battery % isn't synced at the moment.

https://imgur.com/a/OFM7kLO

Set discharge floor to 10%, charge efficiency factor to 97%
EDIT: and battery SOC on reset to "keep SOC"

Thanks!

 

[740GLE]

Post a tTrend of the smart shunt SOC and voltage for the past 5-10 days.

 

[sunshine_eggo]

The SOC value was coming from the BMS while the smart shunt pegged me around 70% I think. I synced it at 100% or float charge but have had to keep syncing it again each time the inverter shuts off since there's now low voltage warning.

I think I enabled virtual switch a while back. I was trying to setup something where shore power was on, but would only charge the battery when it got to a low enough voltage, but I ever quite got it to work properly.

Recommend you disable it.

I'll change those settings once HighTechLab responds in a bit, but it seems like aux relay enabled and pre-alarm are what's causing my issue thus far. I don't have any GX device yet.

Then don't try to connect battery to inverter. The VE.Bus connections are for daisy chaining inverters in parallel or connecting to a GX device.

Set discharge floor to 10%, charge efficiency factor to 97%. Thanks!

For the OP's info, this 10% has nothing to do with anything except the Shunt's "time to go" value, i.e., it's telling you how long it takes to get to 10%.

I would also recommend the following changes:

Charged to 55.0V
Tail current to 6%
Battery SoC on reset to "Keep SoC"

 

[HighTechLab]

Recommend you disable it.



Then don't try to connect battery to inverter. The VE.Bus connections are for daisy chaining inverters in parallel or connecting to a GX device.



For the OP's info, this 10% has nothing to do with anything except the Shunt's "time to go" value, i.e., it's telling you how long it takes to get to 10%.

I would also recommend the following changes:

Charged to 55.0V
Tail current to 6%
Battery SoC on reset to "Keep SoC"

I don't like charged below float voltage because then the system can keep resyncing while there are very low loads in float mode.

Most definitely set Battery SOC on reset to keep SoC, otherwise if you run the battery dead it will jump to 100%

 

[SkepticalTiger]

BMS communication requires a Cerbo-GX and will not fix this issue.

I am 95% sure what is going on here is the SOC has drifted (pretty far) out of calibration. Whether you are using a smartshunt or the SOC tracking on the batteries, the system will only properly recalibrate the meter 100% when they batteries get a full recharge. So, to start with, recharge to 57.6v (absorption).

From there, run some normal loads and see when the batteries are shutting down.

50V is down in the last 10% or so on these packs, so no matter what is causing the shutdown the batteries are empty and the SOC is wrong. I generally recommend all customers fully recharge to 57.6v once per week otherwise the SOC readings can mislead you. We can turn off VS but it's like turning off the A/C in the car because you are out of gas - it's not fixing the bigger issue here.

One other thing I need to address - I found this email went unanswered since 12/6 in one of my newer tech's inbox and I'm pretty sure it's because she needed to discuss it with our tech support manager for some help. I will have a meeting with both of them tomorrow - done means done and it should have not gone this long unresolved. So, thank you guys for bringing this to my attention so quickly to keep my attention on a potential bigger issue at hand.

What do you think about my recent VC Smart Shunt Post?

 

[SkepticalTiger]

Post a tTrend of the smart shunt SOC and voltage for the past 5-10 days.

I lost that last time when the system turned off today. I'll need to keep load or set the battery's shutoff to be 72 hours instead of 48 it seems.

 

[HighTechLab]

I lost that last time when the system turned off today. I'll need to keep load or set the battery's shutoff to be 72 hours instead of 48 it seems.

Why can't you charge the battery? If you have the battery on charge it won't go into sleep mode.

 

[740GLE]

I lost that last time when the system turned off today. I'll need to keep load or set the battery's shutoff to be 72 hours instead of 48 it seems.

The BMS shut off?

The only way the victron smart shunt should lose power (system shutting off) is if the battery terminals went to zero volts.

 

[Checkthisout]

The BMS shut off?

The only way the victron smart shunt should lose power (system shutting off) is if the battery terminals went to zero volts.

Yeah. I mean is that what's occurring?

His BMS is tripping on low cell voltage and that's why the MP won't come on until a/c power is supplied?

 

[HighTechLab]

Most likely. If he is not regularly doing a full charge that will cause the SOC to drift and for him to run out of power.