Victron multiplus-II shutting down

[brackstone]

Just got my multiplus running but I am getting low battery shut down for some reason.

Whe solar MPPT is switched off the inverter runs all ok. I have pulled 50 amps for a few min with no issues.

With the MPPT switched on as soon as I put any load over 10 amps the inverter shuts down with low voltage warning.

So I am assuming this is an MPPT issue. See attached MPPT setting. I am wondering is this is an overvoltage from the MPPT as some times it shuts down the battery BMS

 

[sunshine_eggo]

Battery details needed.

Capacity?

DIY or pre-built?

Known charge state?

Individual cell voltage data?

 

[brackstone]

Batteries are roamer 24v 240aH connected in series, they are fully charged and balanced.

I have just set the victron MPPT absorbtion and float voltage down to 48v and so far the inverter has been running all ok even running my mitra saw. Previous it would shut down as soon as I operated the mitra saw so I am assuming this is an overvoltage coming from the MPPT. Only issue at 48v setting I am not charging now.

 

[sunshine_eggo]

Two 24V in series for 48V MUST be perfectly balanced. It is commonplace for series connected battery imbalance to trigger one battery to over-volt and cut charge.

Are you monitoring the 24V each individually?
Do you have access to the cell data?
You charged each 24V to 28.8V for at least two hours absorption individually and again in parallel while confirming charge current was never interrupted by BMS?

The idea that the MPPT can in some way cause issues with the MP is not the most likely cause. The MPPT can only send current or not send current. However, an imbalanced battery/BMS, particularly one built from individual series batteries, can wreak havoc on a system.

Recommend you:
Disconnect the MP
Enable VictronConnect settings to keep the display on.
Set Expert mode: fixed absorption time of 3 hours and disable tail current if enabled.
Select trending in victronconnect to display battery voltage and current
Monitor the individual 24V batteries with voltmeters.

Charge the batteries to 56V and observe the behavior. It should hit 56V, and the current should slowly taper to zero. If you see any abrupt changes in current or voltage, that's the BMS interfering.

 

[brackstone]

Screen shot of batteries BMS attached. I will have ago at what you said tomorrow. I do not have any victronConnect to the inverter at present.

Reason why I thought it was MPPT issue because the inverter runs all ok with the MPPT switched off or the charge voltage dropped to 48v. On 55v setting the inverter shuts down under load

 

[HRTKD]

Having the solar charge controller contributing power is masking the problem.

If you have a cheap fuse in between the battery and the inverter, that could be the problem. We've seen that before on the forum. It could also be poor connections on the circuit to the battery.

With the system under load for a few minutes, check all your connections/wires with your finger, looking for a hot spot. A connection that is hotter than the other connections is a red flag.

Your batteries look to have well balanced cells. However, I don't see what state of charge the battery BMS thinks it is at. The voltage of 26.4 seems a bit low. I change my 12 volt batteries to 14.2, so yours should be closer to 28.4 at 100% state of charge.

 

[sunshine_eggo]

I would not conclude voltages in the low 3.3V range are in any way indicative of balance. Overwhelming quantity of posts here indicating that batteries with voltages in the operating range rarely have significant voltage deviation even when they are KNOWN to exhibit substantial imbalance above 3.40V/cell.

 

[HRTKD]

I would not conclude voltages in the low 3.3V range are in any way indicative of balance. Overwhelming quantity of posts here indicating that batteries with voltages in the operating range rarely have significant voltage deviation even when they are KNOWN to exhibit substantial imbalance above 3.40V/cell.

I know that you know that I know that. But since no state of charge was provided, it was the only thing I had to go on.

 

[brackstone]

Having the solar charge controller contributing power is masking the problem.

If you have a cheap fuse in between the battery and the inverter, that could be the problem. We've seen that before on the forum. It could also be poor connections on the circuit to the battery.

With the system under load for a few minutes, check all your connections/wires with your finger, looking for a hot spot. A connection that is hotter than the other connections is a red flag.

Your batteries look to have well balanced cells. However, I don't see what state of charge the battery BMS thinks it is at. The voltage of 26.4 seems a bit low. I change my 12 volt batteries to 14.2, so yours should be closer to 28.4 at 100% state of charge.

I have a temp infra red gun and all connections are normal. Fuse and holder are very good. I will recheck all connections tomorrow. Voltage is about 53v on shutdown but maybe a spike that I am not seeing. Video Link showing the shutdown LINK

 

[brackstone]

Whe I have then at 100% again I will give it another try

 

[HRTKD]

In the video, that is a reading from the battery side of the fuse? A reading right at the Multiplus would be helpful also.

 

[brackstone]

In the video, that is a reading from the battery side of the fuse? A reading right at the Multiplus would be helpful also.

This reading was taken from the busbars next to the inverter. If there was any issues with the connections etc would it not shutdown at any state. At present it only shuts down with MPPT on. With MPPT off inverter runs fine

 

[HRTKD]

At present it only shuts down with MPPT on. With MPPT off inverter runs fine

Hmm, that's the opposite of what I thought was happening. Can you post the settings for the solar charge controller?

 

[brackstone]

Hmm, that's the opposite of what I thought was happening. Can you post the settings for the solar charge controller?

Well this was why I keep going back the the MPPT causing the issue. More like overvoltage and the BMS maybe shutting down. I have emailed roamer to find out the charging settings for the battery. Attached is the MPPT settings

 

[brackstone]

Hmm, that's the opposite of what I thought was happening. Can you post the settings for the solar charge controller?

I was running the inverter for 10 min cutting wood with my mitre saw all ok with absobtion and float set to 48v on the MPPT, all was OK. Tomorrow I will see if I can increase this voltage 1v at a time to see when it starts to shut down.

 

[HRTKD]

Yes, if the BMS shuts down it could look like a low voltage situation. 48 volt charge is low. 56 volt bulk is on the upper end.

I think this is your battery: https://roamer.com/products/24-230smart

Specs look OK. The 45 amp charge rate from the solar charge controller shouldn't be a problem at all. But if the BMS has a High Voltage Disconnect value set too low, that could be a problem.

 

[brackstone]

Yes, if the BMS shuts down it could look like a low voltage situation. 48 volt charge is low. 56 volt bulk is on the upper end.

I think this is your battery: https://roamer.com/products/24-230smart

Specs look OK. The 45 amp charge rate from the solar charge controller shouldn't be a problem at all. But if the BMS has a High Voltage Disconnect value set too low, that could be a problem.

Yes thats the battery. Spoke to roamer and 56v charging sould be OK. He also said about making sure the batteries are same state of charge before connecting in series. This is something I did not do so possible this is the issue as one BMS may shut down. Will charge them tomorrow to same sates individually then retest, fingers crossed.

 

[sunshine_eggo]

I know that you know that I know that. But since no state of charge was provided, it was the only thing I had to go on.

It was reporting a 5A load. No better way to pull cell voltages down to the operating range almost instantly then put a load on it. In that case, SoC doesn't matter.

I was running the inverter for 10 min cutting wood with my mitre saw all ok with absobtion and float set to 48v on the MPPT, all was OK. Tomorrow I will see if I can increase this voltage 1v at a time to see when it starts to shut down.

Again, with the trend tab, you can see EXACTLY what the MPPT is doing with voltage and current during charge.

The only thing you've done by setting it to 48V is effectively disconnect it. You need to see what's happening during charge.

Chasing it 1V at a time is not diagnostically meaningful. Set it to the desired absorption voltage and log what happens. The chances of this being battery/BMS related are very high. The chances of it being the charge controller are very low.

You likely missed it, but there was a huge discussion of one battery that would cut voltage when the charge current ended, i.e., it was fine while charging, but when the charging stopped, the BMS would completely cut off EVERYTHING and then turn back on.

Yes thats the battery. Spoke to roamer and 56v charging sould be OK. He also said about making sure the batteries are same state of charge before connecting in series. This is something I did not do so possible this is the issue as one BMS may shut down. Will charge them tomorrow to same sates individually then retest, fingers crossed.

Two 24V in series for 48V MUST be perfectly balanced. It is commonplace for series connected battery imbalance to trigger one battery to over-volt and cut charge.

You charged each 24V to 28.8V for at least two hours absorption individually and again in parallel while confirming charge current was never interrupted by BMS?

 

[brackstone]

It was reporting a 5A load. No better way to pull cell voltages down to the operating range almost instantly then put a load on it. In that case, SoC doesn't matter.



Again, with the trend tab, you can see EXACTLY what the MPPT is doing with voltage and current during charge.

The only thing you've done by setting it to 48V is effectively disconnect it. You need to see what's happening during charge.

Chasing it 1V at a time is not diagnostically meaningful. Set it to the desired absorption voltage and log what happens. The chances of this being battery/BMS related are very high. The chances of it being the charge controller are very low.

You likely missed it, but there was a huge discussion of one battery that would cut voltage when the charge current ended, i.e., it was fine while charging, but when the charging stopped, the BMS would completely cut off EVERYTHING and then turn back on.

You maybe wright about one BMS shutting down this will explain the sudden shutdown which my multimeter is not picking up in time. I have a victron shunt which I need to connect so this may show more. I will balance them tomorrow and reset with the trending on MPPT running. This was one trend I took but will have to do same when it shuts down

 

[sunshine_eggo]

You maybe wright about one BMS shutting down this will explain the sudden shutdown which my multimeter is not picking up in time. I have a victron shunt which I need to connect so this may show more. I will balance them tomorrow and reset with the trending on MPPT running. This was one trend I took but will have to do same when it shuts down
View attachment 145679

Nothing stands out in those numbers. Simply looks like variable power delivery.

Yes... smartshunt! It will actually LOG the data you select for up to 45 days even if the app is not connected. Select the parameters you want in Trends, and it will record them. I don't know if it records everything, but I think it does. It will definitely log the two parameters you select.