Which USB to RS485 converter to use

[stuartornum]

Hi @Frankkkkk

Would you mind letting us know what hardware you are using to communicate with the Pylontech batteries. For example, which USB to RS485 cable you are using, which OS/Hardware etc.

I'm struggling with a Raspberry Pi 3B+ and USB to RS485 adapter (https://www.amazon.com/gp/product/B08RDZVP49)

Cheers!

[Frankkkkk]

Hi @stuartornum ,
I'm using a really cheap one like the one below:

(search terms: USB RS485).

The dip switches must all be down (the first dip switch sets the speed: 115200 vs 9600 Bd).

Cheers and don't hesitate if you need more info !

[Frankkkkk]

PS: I don't know the pinout on the one you showed, but I'm pretty sure that it doesn't match the Pylontech RJ45 pinout ! You'd need a custom RJ45 patch cable (easy to crimp).

It's easy to do with the one I showed above because you can just take a standard RJ45/ethernet cable, cut it in half and take the two strands you're interested in

[stuartornum]

Awesome, thanks @Frankkkkk - I've ordered exactly the same from Amazon. I also asked the question to the seller regarding the pinout for the converter I have... no response yet. I'll keep you posted... thanks again!

[stuartornum]

Hi @Frankkkkk ,

I managed to get my hands on the USB RS485 adapter you referenced above. Also, made a new cable from some CAT6 on to a RJ45 (568b). As per the Pylontech manual it says pin 7 and 8 are recommended for RS485, so converting that to 568b we get (Pin 7: brown/white, Pin 8: brown).

I get the following when trying to run the library:
`

import pylontech
p = pylontech.Pylontech()
print(p.get_values())
Traceback (most recent call last):
File "", line 1, in
File "/home/pi/python-pylontech/pylontech/pylontech.py", line 211, in get_values
d = self.get_values_fmt.parse(f.info[1:])
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 288, in parse
return self.parse_stream(io.BytesIO(data), **contextkw)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 300, in parse_stream
return self._parsereport(stream, context, "(parsing)")
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 312, in _parsereport
obj = self._parse(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 2120, in _parse
subobj = sc._parsereport(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 312, in _parsereport
obj = self._parse(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 2653, in _parse
return self.subcon._parsereport(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 312, in _parsereport
obj = self._parse(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 2413, in _parse
e = self.subcon._parsereport(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 312, in _parsereport
obj = self._parse(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 2120, in _parse
subobj = sc._parsereport(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 312, in _parsereport
obj = self._parse(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 2653, in _parse
return self.subcon._parsereport(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 312, in _parsereport
obj = self._parse(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 2413, in _parse
e = self.subcon._parsereport(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 312, in _parsereport
obj = self._parse(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 703, in _parse
obj = self.subcon._parsereport(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 312, in _parsereport
obj = self._parse(stream, context, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 1041, in _parse
data = stream_read(stream, self.length, path)
File "/home/pi/.local/lib/python3.7/site-packages/construct/core.py", line 91, in stream_read
raise StreamError("stream read less than specified amount, expected %d, found %d" % (length, len(data)), path=path)
construct.core.StreamError: Error in path (parsing) -> Module -> GroupedCellsTemperatures
stream read less than specified amount, expected 2, found 1`

I also switched the brown/brown-white wires around on the RS485-to-USB adapter to see if I got a different output, I did...:

`

p = pylontech.Pylontech()
print(p.get_values())
Traceback (most recent call last):
File "", line 1, in
File "/home/pi/python-pylontech/pylontech/pylontech.py", line 208, in get_values
f = self.read_frame()
File "/home/pi/python-pylontech/pylontech/pylontech.py", line 167, in read_frame
f = self._decode_hw_frame(raw_frame=raw_frame)
File "/home/pi/python-pylontech/pylontech/pylontech.py", line 148, in _decode_hw_frame
assert got_frame_checksum == int(frame_chksum, 16)
ValueError: invalid literal for int() with base 16: b''`

Any thoughts?

Thanks again for your help! Really appreciate it.

(I'm using a Raspberry Pi 3b+)

[Frankkkkk]

Hi,

How are your dip switches set ? They should be all four off (down). Which pylontech modules have you got (model) ?

It would be great to show the received raw frame by either adding a print(raw_frame) after here or by launching wireshark and capturing the serial port communications.

Cheers !

[Frankkkkk]

I suppose that your first wiring must be correct as the frame passed the checksum validation.

Maybe your setup is a bit different than mine and we must change the frame protocol. If you can manage to dump the raw frame I can try to check the differences and patch the lib ;-)

[stuartornum]

Hi @Frankkkkk , thanks for getting back to me.

• All DIP switches are down: https://imgur.com/a/pIJbQBH
• I have 1x US3000 Plus and 1x US2000 Plus
• I've switched back the wires to be the first way around

Debug out from printing L169:
b'~2002460010F011020F0CCD0CCE0CCC0CCE0CCB0CCC0CCD0CCC0CCD0CCB0CCC0CCD0CCD0CCE0CCC050BE10BCD0BCD0BD70BCDFFC3BFFDFFFF04FFFF0234007F300121100F0CCA0CCA0CCB0CCC0CCA0CCC0CCB0CCB0CCB0CCB0CCB0CCA0CCC0CCC0CCB050BEB0BCD0BCD0BCD0BC3FFD1BFE5FFFF04FFFF0292005FB400C350C4A7\r'

Cheers

[Frankkkkk]

Well, I managed to decode part of the frame:

Container: 
    NumberOfModules = 2
    Module = ListContainer: 
        Container: 
            NumberOfCells = 15
            CellVoltages = ListContainer: 
                3.277
                3.278
                3.276
                3.278
                3.275
                3.276
                3.277
                3.276
                3.277
                3.275
                3.276
                3.277
                3.277
                3.278
                3.276
            NumberOfTemperatures = 5
            AverageBMSTemperature = 30.41
            GroupedCellsTemperatures = ListContainer: 
                30.21
                30.21
                30.31
                30.21
            Current = -6.1
            Voltage = 49.149
            Power = -299.8089
            RemainingCapacity = 65.535
            TotalCapacity = 65.535
            CycleNumber = 564
    foobar = 16
    Module2 = ListContainer: 
        Container: 
            NumberOfCells = 15
            CellVoltages = ListContainer: 
                3.274
                3.274
                3.275
                3.276
                3.274
                3.276
                3.275
                3.275
                3.275
                3.275
                3.275
                3.274
                3.276
                3.276
                3.275
            NumberOfTemperatures = 5
            AverageBMSTemperature = 30.51
            GroupedCellsTemperatures = ListContainer: 
                30.21
                30.21
                30.21
                30.11
            Current = -4.7
            Voltage = 49.125
            Power = -230.88750000000002
            RemainingCapacity = 65.535
            TotalCapacity = 65.535
            CycleNumber = 658
    greedy = ListContainer: 
        0
        95
        180
        0
        195
        80
    TotalPower = -299.8089
    StateOfCharge = 1.0

But I specified the protocol manually:

    get_values_fmt = construct.Struct(
        "NumberOfModules" / construct.Byte,
        "Module" / construct.Array(1, construct.Struct(
            "NumberOfCells" / construct.Int8ub,
            "CellVoltages" / construct.Array(construct.this.NumberOfCells, ToVolt(construct.Int16sb)),
            "NumberOfTemperatures" / construct.Int8ub,
            "AverageBMSTemperature" / ToCelsius(construct.Int16sb),
            "GroupedCellsTemperatures" / construct.Array(construct.this.NumberOfTemperatures - 1, ToCelsius(construct.Int16sb)),
            "Current" / ToAmp(construct.Int16sb),
            "Voltage" / ToVolt(construct.Int16ub),
            "Power" / construct.Computed(construct.this.Current * construct.this.Voltage),
            "RemainingCapacity" / DivideBy1000(construct.Int16ub),
            "_undef1" / construct.Int8ub,
            "TotalCapacity" / DivideBy1000(construct.Int16ub),
            "CycleNumber" / construct.Int16ub,
        )),
        "foobar" / construct.Int8ub,
        "foobar" / construct.Int8ub,
        "foobar" / construct.Int8ub,
        "foobar" / construct.Int8ub,
        "foobar" / construct.Int8ub,
        "foobar" / construct.Int8ub,
        "Module2" / construct.Array(1, construct.Struct(
            "NumberOfCells" / construct.Int8ub,
            "CellVoltages" / construct.Array(construct.this.NumberOfCells, ToVolt(construct.Int16sb)),
            "NumberOfTemperatures" / construct.Int8ub,
            "AverageBMSTemperature" / ToCelsius(construct.Int16sb),
            "GroupedCellsTemperatures" / construct.Array(construct.this.NumberOfTemperatures - 1, ToCelsius(construct.Int16sb)),
            "Current" / ToAmp(construct.Int16sb),
            "Voltage" / ToVolt(construct.Int16ub),
            "Power" / construct.Computed(construct.this.Current * construct.this.Voltage),
            "RemainingCapacity" / DivideBy1000(construct.Int16ub),
            "_undef1" / construct.Int8ub,
            "TotalCapacity" / DivideBy1000(construct.Int16ub),
            "CycleNumber" / construct.Int16ub,
        )),
        "greedy" / construct.GreedyRange(construct.Byte),
        "TotalPower" / construct.Computed(lambda this: sum([x.Power for x in this.Module])),
        "StateOfCharge" / construct.Computed(lambda this: sum([x.RemainingCapacity for x in this.Module]) / sum([x.TotalCapacity for x in this.Module])),

    )

There seems to be some extra bytes sent after the first module (written as foobar in the construct proto). So, my questions are:

• Is the first module an US3000 ?
• Can you try launching the program with only the US2000 connected (do a powercycle first) ? Do it work ?
• Same question for US3000
• Can you try by swapping the master/slave modules ?

Interesting though

Cheers !

[Frankkkkk]

And the code if you want to try manually:

    def get_values(self):
        #self.send_cmd(2, 0x42, b'FF')
        #f = self.read_frame()
        rf =  b'~2002460010F011020F0CCD0CCE0CCC0CCE0CCB0CCC0CCD0CCC0CCD0CCB0CCC0CCD0CCD0CCE0CCC050BE10BCD0BCD0BD70BCDFFC3BFFDFFFF04FFFF0234007F300121100F0CCA0CCA0CCB0CCC0CCA0CCC0CCB0CCB0CCB0CCB0CCB0CCA0CCC0CCC0CCB050BEB0BCD0BCD0BCD0BC3FFD1BFE5FFFF04FFFF0292005FB400C350C4A7\r'
        ff = self._decode_hw_frame(raw_frame=rf)
        f = self._decode_frame(ff)
        print(f)
        print(f.info[1:])

        # infoflag = f.info[0]
        d = self.get_values_fmt.parse(f.info[1:])
        return d

[stuartornum]

Hi @Frankkkkk ,

Apologies for the delay in getting back to you:

• Is the first module an US3000 ? - Yes
• Can you try launching the program with only the US2000 connected (do a powercycle first) ? Do it work ? - It DOES work perfectly with just the US2000 connected!!
• Same question for US3000 - It does work perfectly with the US3000 on it's own as well!!!
• Can you try by swapping the master/slave modules ? - I'll read up on how to do this now and get back to you.

Thanks for your help on this, it's really is appreciated

[stuartornum]

I believe I've switched the US2000 to become the master, however, the documentation says to always use the US3000 as the primary when you have a mixture of US2000's/US3000's.

Here is the output:

    NumberOfModules = 2
    Module = ListContainer: 
        Container: 
            NumberOfCells = 15
            CellVoltages = ListContainer: 
                3.287
                3.289
                3.288
                3.287
                3.287
                3.289
                3.289
                3.288
                3.286
                3.287
                3.287
                3.288
                3.288
                3.287
                3.288
            NumberOfTemperatures = 5
            AverageBMSTemperature = 30.11
            GroupedCellsTemperatures = ListContainer: 
                30.11
                30.11
                30.21
                30.11
            Current = -1.8
            Voltage = 49.315
            Power = -88.767
            RemainingCapacity = 29.0
            TotalCapacity = 50.0
            CycleNumber = 659
        Container: 
            NumberOfCells = 15
            CellVoltages = ListContainer: 
                3.288
                3.289
                3.289
                3.288
                3.289
                3.288
                3.288
                3.29
                3.289
                3.289
                3.289
                3.289
                3.289
                3.29
                3.289
            NumberOfTemperatures = 5
            AverageBMSTemperature = 30.21
            GroupedCellsTemperatures = ListContainer: 
                30.21
                30.21
                30.31
                30.21
            Current = -1.7
            Voltage = 49.333
            Power = -83.86609999999999
            RemainingCapacity = 43.66
            TotalCapacity = 8.464
            CycleNumber = 565
    TotalPower = -172.63309999999998
    StateOfCharge = 1.242816091954023

I'm not sure how much I believe some of the numbers, "StateOfCharge" for example...?

[Frankkkkk]

Hi,
No problem for the delays ! :-)
Interesting results 🤔

I suppose we could patch the decoding to handle US3000 as primary modules.. It's strange though. Sadly I don't have one so I can't really test this edge case. Maybe we could add a warning in the readme as a workaround.

As for the StateOfCharge, it's meant to be a percent (0-1: sum(all remaining capacities)/sum(total capacities)). However in your case the US3000 states a RemainingCapacity of 43 but a TotalCapacity of... 8.464 😦 which thus skews the calculation

If that's okay with you, I'll just add a warning for this edge case in the readme, and maybe in the future we can fix the US3000-US2000 bug ?

Cheers

[petero-dk]

I would like to assist on this, what would be the preferred next steps. I have both US2000 and US3000 with the 3000 as the primary right now