Concerns with my system

[MrPsychedelic]

Hey guys. My system has been running great but today I'm not sure what happened.

I was away for a couple days and when I left batteries were around 45%. It's a 48V system with 29Kwh of battery. 2 sets of 304Ah. I don't get much solar at all and when I came back it said 100% which I found odd. I should of checked voltage but I wasn't thinking too.

Today it said 68% with 47.4V and I was running my minisplit heater and a space heater on a victron multiplus 5k and it shut the inverter off due to low battery.

I checked the BMS and it's showing the cells at 47.19V each pack. I'm not good at knowing the volts to battery left so I'm hoping someone here can help me understand what's going on.

Is my shunt bad? Is it something else? What can I do to figure it out?

 

[Nobodybusiness]

Hey guys. My system has been running great but today I'm not sure what happened.

I was away for a couple days and when I left batteries were around 45%. It's a 48V system with 29Kwh of battery. 2 sets of 304Ah. I don't get much solar at all and when I came back it said 100% which I found odd. I should of checked voltage but I wasn't thinking too.

Today it said 68% with 47.4V and I was running my minisplit heater and a space heater on a victron multiplus 5k and it shut the inverter off due to low battery.

I checked the BMS and it's showing the cells at 47.19V each pack. I'm not good at knowing the volts to battery left so I'm hoping someone here can help me understand what's going on.

Is my shunt bad? Is it something else? What can I do to figure it out?

Where are you measuring the SOC?

The batteries themselves or a True shunt?
Does your shunt have the correct capacity input?

If you are relying on an inverter to tell you SOC it’s usually wrong.

I use voltage control vs SOC for this reason.
YMMV.

 

[BTOdell]

It sounds like your BMS/shunt reset its internal SOC value.

Are you using lithium batteries or lead acid? Are you using a Victron shunt?

 

[crowl]

use Voltages if you can instead. 54.4 - 100 SOC, 47.8 is 1-2% SOC. Something is wrong. You have to charge it 100% so shunt recalibrates.
How do I use it. I charge to 54v which corresponds 99 SOC and discharge to 51.6v which corresponds 25% SOC. And never go below.

 

[MrPsychedelic]

Where are you measuring the SOC?

The batteries themselves or a True shunt?
Does your shunt have the correct capacity input?

If you are relying on an inverter to tell you SOC it’s usually wrong.

I use voltage control vs SOC for this reason.
YMMV.

I think I should learn voltage for sure cus of this. 47V seems like it's near the bottom of the batteries state of charge

Measuring the SOC from the victron shunt, the capacity input was correct before I left for the holidays. It did get extremely cold and I'm wondering if that messed things up. I was nervous to leave the heat on and just trusted the JK BMS to keep everything safe. Might of been a bad move.

Is it normal for the victron shunt to reset itself?

 

[MrPsychedelic]

It sounds like your BMS/shunt reset its internal SOC value.

Are you using lithium batteries or lead acid? Are you using a Victron shunt?

Lithium batteries and yes victron shunt. The waterproof one.

Is it normal for the shunt to reset itself?

 

[MrPsychedelic]

use Voltages if you can instead. 54.4 - 100 SOC, 47.8 is 1-2% SOC. Something is wrong. You have to charge it 100% so shunt recalibrates.

Taking a screenshot of those values lol. I have it plugged into the house now going to let it charge all night and day tomorrow till the BMS goes to float

 

[crowl]

Taking a screenshot of those values lol. I have it plugged into the house now going to let it charge all night and day tomorrow till the BMS goes to float

Yes, learn by heart three main values:
54.4 ~ 100%
54.0 ~ 99%
51.6 ~ 25%.
50 ~ <5%.
That's all you need to know.

 

[Nobodybusiness]

I think I should learn voltage for sure cus of this. 47V seems like it's near the bottom of the batteries state of charge

Measuring the SOC from the victron shunt, the capacity input was correct before I left for the holidays. It did get extremely cold and I'm wondering if that messed things up. I was nervous to leave the heat on and just trusted the JK BMS to keep everything safe. Might of been a bad move.

Is it normal for the victron shunt to reset itself?

I have a Victron shunt and I have never known it to reset on its own.

There is the ability in the app to reset it manually.

If you can charge the batteries Manually until full.
Make sure your capacity # is correct then go in the app and manually reset to 100% SOC.

Check your settings on your BMS and Inverter/ charger also..

Watch and see if it drifts that wildly again.

Not sure what happened though.

 

[BTOdell]

Lithium batteries and yes victron shunt. The waterproof one.

Is it normal for the shunt to reset itself?

Go into the Victron SmartShunt settings. "Battery" > "Battery SOC on reset", and make sure it's set to "Keep SOC".
I don't know what would cause the shunt to lose power and reset.
If the shunt is already set to "Keep SOC", then I can't think of what else would have caused it to reset to 100% SOC.

Maybe your solar kicked on just long enough to trigger your shunt's synchronization criteria. For lithium batteries, your shunt settings should be:

• Discharge floor: 10-20%
• Peukert exponent: 1.05
• Charge efficiency factor: 99%
• Current threshold: 0.05-0.10

Additionally, you might want to increase the "charged detection time" higher than 3 minutes and make sure your shunt's "charged voltage" is aligned with the absorption voltage of your inverter charger and/or solar charge controller.

 

[MrPsychedelic]

I have a Victron shunt and I have never known it to reset on its own.

There is the ability in the app to reset it manually.

If you can charge the batteries Manually until full.
Make sure your capacity # is correct then go in the app and manually reset to 100% SOC.

Check your settings on your BMS and Inverter/ charger also..

Watch and see if it drifts that wildly again.

Not sure what happened though.

I'm gonna keep them on shore power and let them fully charge over night and throughout tomorrow keeping an eye on their voltages.

I'm wondering if the BMS shut off charging to the batteries, but the shunt still took the solar as charging and that's why it showed 100%. Or the cold just made everything wonky and it just auto reset. I hate the cold lol

 

[MrPsychedelic]

Go into the Victron SmartShunt settings. "Battery" > "Battery SOC on reset", and make sure it's set to "Keep SOC".
I don't know what would cause the shunt to lose power and reset.
If the shunt is already set to "Keep SOC", then I can't think of what else would have caused it to reset to 100% SOC.

Maybe your solar kicked on just long enough to trigger your shunt's synchronization criteria. For lithium batteries, your shunt settings should be:

• Discharge floor: 10-20%
• Peukert exponent: 1.05
• Charge efficiency factor: 99%
• Current threshold: 0.05-0.10

Additionally, you might want to increase the "charged detection time" higher than 3 minutes and make sure your shunt's "charged voltage" is aligned with the absorption voltage of your inverter charger and/or solar charge controller.

I'll double check the settings I have currently and update accordingly. I appreciate the help! I'm wondering if the BMS shut off charging cus of the cold, but the shunt was still thinking the solar was charging so it kept going up because of that, but that wouldn't make much sense since the SOC should be based off voltage I would think?

I do believe I put the charged detection time to 5 minutes, maybe I should up it a little more?

 

[Nobodybusiness]

I'm wondering if the BMS shut off charging to the batteries, but the shunt still took the solar as charging and that's why it showed 100%. Or the cold just made everything wonky and it just auto reset. I hate the cold lol

If physically setup correctly once the BMS shutdown for whatever reason then the current should stop regardless if you had solar or any power available or not.

You shouldn’t have anything accepting power on the battery side of the shunt except batteries.

 

[MrPsychedelic]

If physically setup correctly once the BMS shutdown for whatever reason then the current should stop regardless if you had solar or any power available or not.

You shouldn’t have anything accepting power on the battery side of the shunt except batteries.

I have a victron lynx distributer with solar, inverter, and 12V system. I have the shunt connected to the main negative on that lynx.

I have the both batteries connected to a positive and negative bus bar and from there one wire each pos/neg to the lynx. I figured the solar wouldn't listen the BMS since it's wired to the lynx. I assumed it would push power to the lynx but not let it go back to the battery as it's would stop at the BMS right before the battery.

These are all assumptions and just how my brain thought it worked

 

[Brett V]

It sounds like your voltage dropped to a critical low and the BMS shut down, including power to the smart shunt. Then you got just enough sun to wake things up but the shunt didn’t keep its SOC and reset. In any case, 47.4 volts is a depleted battery

 

[MrPsychedelic]

It sounds like your voltage dropped to a critical low and the BMS shut down, including power to the smart shunt. Then you got just enough sun to wake things up but the shunt didn’t keep its SOC and reset. In any case, 47.4 volts is a depleted battery

I followed Andy's from off grid garage settings of his BMS, the low voltage cutoff is 2.65V per cell, that feels awful low after learning this. Should I raise that up?

Also the BMS is showing .2V lower than the shunt is reading. Is that normal?

 

[Brett V]

I followed Andy's from off grid garage settings of his BMS, the low voltage cutoff is 2.65V per cell, that feels awful low after learning this. Should I raise that up?

Also the BMS is showing .2V lower than the shunt is reading. Is that normal?

You only need one cell to go low to trip the BMS. How well are your cells balanced? I wouldn’t be concerned with changing any of those settings. You pulled more from your batteries than you put in and the system worked as intended.

The voltage you’re seeing on the BMS isn’t unusual and can probably be calibrated but you should be checking first with a decent DVM so you know what you’re actually dealing with. I’m currently discharging and my shunt is showing the same voltage as all four BMS.