BMS communication issues

[cojmh]

Hi all,

I am quite new here and have enjoyed reading through other areas of the forum over the past few weeks.

I have had a 4.7KW PV system installed on my house since Dec 2015 and it has been great - but we have ended up sending a lot of the generated power to the grid as we simply could not use it.

Given the current turmoil in the energy market we decided to upgrade to batteries last month (something we always planned to do at some point) and I was told our system (a Solax SKU5000e) would work with the Pylontech batteries. Something I confirmed with multiple suppliers. So we have taken the plunge and got a stack of 4* US3000C batteries. Everything was quite straight forward for the install but I am having issues with the communication between the inverter and master battery.

I have contacted Solax UK and they sent me the correct lead as apparently it is different to the one in the Pylontech external cable set. The Solax cable says it is for LG batteries but I am told this is the correct cable. However when I check the battery status on the inverter (which reports the batteries are OK) it states that the "BMS Disconnected"

Unfortunately I think I have got to the end of the help that was being supplied by SolaxUK and the seller is proving difficult to pin down - Even though the batteries were new.

So I was wondering if anyone else had the same setup as me (Solax SKU5000e and Pylontech US3000C batteries) and if so, how you got it working?

Thanks in advance for any help.

Jon

[Joeboy]

Hi all,

I am quite new here and have enjoyed reading through other areas of the forum over the past few weeks.

I have had a 4.7KW PV system installed on my house since Dec 2015 and it has been great - but we have ended up sending a lot of the generated power to the grid as we simply could not use it.

Given the current turmoil in the energy market we decided to upgrade to batteries last month (something we always planned to do at some point) and I was told our system (a Solax SKU5000e) would work with the Pylontech batteries. Something I confirmed with multiple suppliers. So we have taken the plunge and got a stack of 4* US3000C batteries. Everything was quite straight forward for the install but I am having issues with the communication between the inverter and master battery.

I have contacted Solax UK and they sent me the correct lead as apparently it is different to the one in the Pylontech external cable set. The Solax cable says it is for LG batteries but I am told this is the correct cable. However when I check the battery status on the inverter (which reports the batteries are OK) it states that the "BMS Disconnected"

Unfortunately I think I have got to the end of the help that was being supplied by SolaxUK and the seller is proving difficult to pin down - Even though the batteries were new.

So I was wondering if anyone else had the same setup as me (Solax SKU5000e and Pylontech US3000C batteries) and if so, how you got it working?

Thanks in advance for any help.

Jon

Hey Jon, you've done full power cycles of the inverter and batteries? What settings have you played with in the inverter or are you doing it thru an app. I have a different inverter to you but have found it squirelly to set up when adding new batteries.
First thing first, which battery port have you plugged into for the bms? Here's my setup. Note grey bms comms lead position on master battery.

[cojmh]

Hi Joe,

Thanks for the swift response.

I have plugged the cable into the A/CAN port (which I believe is the same port you have yours in). I have left all of the DIP switches as 0 (off)

I have plugged the other end of the cable into the BMS port on the inverter and made sure the cable was in the correct way around (i.e. Inverter end of cable in the inverter and the battery end of the cable in the battery).

I have cycled the batteries on/off multiple times but I have never shut down the inverter and restarted that (It has restarted a couple of times by itself and I am not sure if that is related to me adding the batteries). This is something I can try a later this evening though if you think it might help. I have tried changing DIP switch one as it relates to the communication speed setting but this did not seem to help.

What is worrying me slightly is that SolaxUK who were helping me have stated that their inverter has not been tested with the US3000C and as such it might not be supported. I was told (but I cannot remember who by) that there was no real differences on the BMS side between the different units from a communication with the inverter perspective. So I am just worried I have a stack of batteries that I cannot use since then SolaxUK have gone silent.

In terms of the settings on the inverter. Once I managed to find the installer code, I checked the settings on the inverter directly (not through an app) and it was set to Lithium batteries with a cut off at 20% State of charge - This is the only thing I have changed on the inverter and I changed it to 10% state of charge cut off. Everything else seemed to be standard.

Thank you again for taking the time to reply

Jon

[Joeboy]

No worries, I don't know that inverter to be clear.

On my own system the first thing I would check for would be a deep delve into battery options. My unit lists pylontech as an option. Next I'd do an inverter reboot and see if the inverter sees the batteries. Lastly have you pushed the red button on your master battery when all is up and running? Marked sc I think? The sequence for me is

All batteries off

Inverter setting
Reboot inverter

Turn on battery rocker switches one at a time top down starting with master battery.

Push red sc button on master battery

[cojmh]

Hi Joe,

I will give that a go and see if rebooting the inverter after the batteries sorts it out.

In terms of the documentation from Pylontech, the batteries should work with Solax and there is no distinction between the different battery units. From Solax they simply state US2000.

In terms of the red button, yes I have pressed that to bring the batteries online.

The first time I did that, the batteries all charged from the grid. Since then the batteries come on and sit there with all the SOC LEDs lit up and the run LED initially on all the time then after a few mins the run LED starts to flash - from looking this up it would appear that it has gone into idle mode and just waits in that mode till I turn them all of and try something else.

The inverter is able to see the batteries because it picks up all of the battery bank voltage and gives a % full number. However I am certain that it is doing this from the main power cables and not the communication cables. It must be getting the percentage full figure as an estimate from the battery voltage.

Just on a side note - looking at your system (which looks great by the way) there seems to be an extra Positive and negative power cable that I cannot quite figure out why it is there. On my setup all of the batteries are daisy chained with the main feed cables going to the first and last battery. So I effectively have a single positive terminal not connected on the master battery and a single negative terminal not connected on the last battery - but I have noticed all of the terminals are connected on your setup. So I was wondering if I had done something wrong with my cables?

Thanks,

Jon

[Joeboy]

Nah, Its not you. I use those last two ports to run power to an offgrid back up inverter to power lights n that. Right enough it sounds like your inverter isn't issuing the command to discharge. Also worth checking all your settings in inverter to make sure it is set to discharge batteries?

Beyond this point i'd be guessing unless i was in about it or had more knowledge of that inverter. Hopefully someone will be along, all the best with the power cycle. It comes in more often than people think!

[Tinbum]

Can you post a picture of the 2 ends of the Com cable showing the wires in the ends so we can see which pins are connected?

[Tinbum]

I don't know that inverter but looking at the instructions.

Have you set up the 'Work mode' and 'Charge' settings in the inverter? ie Lithium Note if their is no BMS coms the inverter will use the defaults and the 'charge cut volts' is set too high. Max for a US3/2000C is 53.2v

[Swwils]

The newer models have the dip switch reversed.

So 0 0 0 0 is

RS485:115200
CAN terminal
resistance: connected

Also the comms cable is different, Pin1/2/3 on both A/CAN and
B/RS485 need to be NULL and the pin order for GND changed.

Hopefully this helps.

[Joeboy]

The newer models have the dip switch reversed.

So 0 0 0 0 is

RS485:115200
CAN terminal
resistance: connected

Also the comms cable is different, Pin1/2/3 on both A/CAN and
B/RS485 need to be NULL and the pin order for GND changed.

Hopefully this helps.

Well thats likely to be it then, if the inverter supplier sent him a cable for their unit tested on us2000's it's not going to work. OP suggest you show cable and delve manuals. I'm sure you could get a cable made up online so it was us2000 at the inverter end and us3000 comms at the can port on battery? Are you handy enough to do a choc block wire on your own to test?