Hi All, My first post here!

I have an Axpert VMIII 5kW inverter, 2 x 3.5kW Pylontech (US3000) batteries and 3kW of panels to charge them.

My setup is just a few months old and has been working fine up till now, but yesterday I noticed the solar charging just stalled at around 18A. After a bit of investigating I found the issue was the Max Charging Current had reset to 20A, I used the app to change it back to 50A, a few seconds later and it's reset back to 20A  Finally a power cycle fixed it and I got it back to 50A, but I woke up this morning and it's reset itself back to 20A again and I had to power it on and off again to get it back up.

Additional information, I have the Pylontech batteries connected to the inverter using the comms cable and using the Pylon setting as the battery type, so it's possible the batteries could be changing the setting, perhaps they limit charging amps due to cold weather in the morning? Also, Due to loadshedding I changed the Solar Only charging option to Solar + Utility so i could charge the battery off mains.

Any help or advice would be appreciated. Thanks.

9 minutes ago, deenem said:

solar charging just stalled at around 18A. After a bit of investigating I found the issue was the Max Charging Current had reset to 20A, I used the app to change it back to 50A, a few seconds later and it's reset back to 20A

Yes, this is the firmware setting the limit down in response to messages from the BMS. You may have a cell out of balance a bit; given time and the reduced charging current, it should sort itself out. When using the battery type setting at PyL or one of the new options, just let the BMS manage the battery settings.

Of course, this code is all fairly new, and it's possible for bugs to be present 😏. If you're really sure it's doing the wrong thing, gather as much data as possible, post it here, and we can try and get it fixed. For now, give it some time because the likelihood is that it's a balancing event.

It could also be reducing the charge current for cold weather, but I'd expect the cells to have to get down below about 5°C for this to be needed. LFP should not be charged at all below 0°C.

Hey, thanks for the response. It does seem to be the battery BMS. I noticed it always limits the input to 20A when it gets to 87% full, then down to 10A at about 95%.

The battery used to run down to 20% overnight but due to loadshedding I've changed things so it's only around 40% in the morning now. 

I will leave it tomorrow morning and see it it gets out of the 20A limit at any point

Just a follow up for someone reading this. I swapped the RS485 cable from one battery to the other and changed the Link 0 and Link 1 connections to make it the new 'leader' and that seems to have resolved it. Just hoping it's not a faulty BMS on the other battery.