Marvel 280Ah battery, Triple A 4000 inverter, 24V system
I need help please — once I connected the BMS, it charges from the grid at 50A according to the settings. But during the day, when there’s sunlight, the charging current drops to 20A. When I manually raise it back to 50A, it goes down again to 20A on its own. Is this normal?

More info on number of panels, solar charging current setting, charge priority etc would be helpful.

3 minutes ago, Denns said:

More info on number of panels, solar charging current setting, charge priority etc would be helpful.

Edited September 16, 2025Sep 16 by Sting

Well I am not sure about your inverter but with mine and another I had before, if you set it to solar and utility, when the MPPT is on and you are above the cut off voltage for the battery, only solar charges and load AND both solar and battery supply the load if your load is too much for your solar until the cut off is hit and then utility comes on.

So even though you have it on solar and utility, the utility only kicks in if you are below the battery cut-off voltage. So increase the solar charging to 50A and reduce the Utility charging to 50A ASSUMING your max battery charging is more than 100A.

To be on the safe side, make the max charging one 50A and put the utility one on 30A. I set my solar one higher personally because these days utility is always there so it can take longer to charge but thats your choice. Change the charge setting that is on 20A to a higher value but keep within the max charging of the battery.

I am assuming you have a setting for solar charging current also. If not then lower the Max AC charging and increase the MAX charging to a higher value. The difference would probably be the solar charging current.

Edited September 16, 2025Sep 16 by Denns

On 9/16/2025 at 12:08 PM, Denns said:

Well I am not sure about your inverter but with mine and another I had before, if you set it to solar and utility, when the MPPT is on and you are above the cut off voltage for the battery, only solar charges and load AND both solar and battery supply the load if your load is too much for your solar until the cut off is hit and then utility comes on.

So even though you have it on solar and utility, the utility only kicks in if you are below the battery cut-off voltage. So increase the solar charging to 50A and reduce the Utility charging to 50A ASSUMING your max battery charging is more than 100A.

To be on the safe side, make the max charging one 50A and put the utility one on 30A. I set my solar one higher personally because these days utility is always there so it can take longer to charge but thats your choice. Change the charge setting that is on 20A to a higher value but keep within the max charging of the battery.

I am assuming you have a setting for solar charging current also. If not then lower the Max AC charging and increase the MAX charging to a higher value. The difference would probably be the solar charging current.

Thank you for replay

Update :

When the grid power comes on and there's no sunlight, the inverter charges at 70 amps, as per the AC charging settings.

But when the solar card is active and grid power arrives, the total charging current drops to only 20 amps. However, if I turn off the solar panel breaker, the charging current goes back up to 70 amps.

Note: In both cases, the battery state of charge is between 60% and 70%.

System specs:

- Inverter: Triple A ( voltronic vm iii ) 4000 w

- Battery: Marvel ML 280A 24V lithium

- Connected to a BMS

Edited September 18, 2025Sep 18 by Sting