Ben Harper

I have two Solis S6 Pro 8KW inverters, at two different houses. The first one was installed in March 2025, and the second one in June 2026. The newer (2026) unit seems to have a higher threshold before the fans switch on (somewhere around 3kw, vs 2kw for my 2025 unit), which makes me wonder if the fan speed is controllable via the firmware. But my real question is this - are the fans physically capable of variable speed, or are they fixed speed? Because on cold days (eg ambient 20C), surely the fans can spin slower when the load is low (eg 2.5KW). I'm curious about the engineering/design decision to make the fans either on/off versus variable speed, depending on ambient temperature and load?

One more interesting plot. This is at night when the house is running off batteries. It's interesting how low the voltage of the bad cell drops. My low SOC limit of 40% kicked in there at 4:30 AM, which is why the voltage stopped dropping. I normally run down to 25%, but since I've been getting this trouble lately, I've raised my lower limit.

I've contacted thepowerstore.co.za where I bought it from, and they're going to assist me getting the RMA done with the distributor. Thank you thepowerstore.co.za! I did not register for the extended warranty unfortunately.

This battery was installed in 2022. I guess I contact the store where I bought it?

Yes it is indeed cell 8. I've checked now as it's discharging, and cell 8 drops much faster than all the others. What are my chances for getting a warranty claim? I installed all my kit myself, so I don't have certificates etc. Any place I should look around in the cape town area for somebody who can replace a cell? That yellow line is cell 8. It's the culprit when charging, and also when discharging. This battery was the 2nd one I bought, so I don't think it's just an age thing.

Hi @Tinbum This is batteryview shortly after it reached 100% SOC (which took 4 hours after the other batteries reached 100%). I don't see anything in the logs. Would I only see alarms in the logs if batteryview was connected and recording while the alarm happened? Also, why do you say to erase the serial number?

@Tinbum Yes - VMin/VMax is very interesting: What does it mean though !?

For me, the voltages are coming out of this: https://esphome.io/components/pylontech/, so they're emitted by the batteries.

@Nexuss I've just taken a careful look at the battery cable lengths, and if you sum up the total length of black + orange cable, then all 3 batteries have equal cable length. For example, if you say that the long cables to the inverter are length "10", and the short connector cables are length "1", then the top and bottom batteries get 10 + 12 = 22 (counting all the cable length in aggregate). The middle battery gets 11 + 11 = 22. In other words, the top and bottom batteries have shorter orange/black, but longer black/orange. So total resistance of the two halves would be the same. Surely that's what matters? Anyway - I'm still puzzled and vaguely worried about the middle battery's "underperformance". It seems like it's getting worse over time - i.e. the pause between batteries 1&3 reaching 100% and then waiting for battery 2, seems to be increasing. Next week I'm going to try flashing them all with the latest firmware, and then swapping them around to see if it makes any difference.

Hi @mocodo , My memory is a bit fuzzy on this, but as far as I can recall, this is what I used to connect batteryview to my Pylontech UP5000. I believe I connected it to the RS232 port (which I think is called the Console port). That little RS232 green adapter has no chip - it's purely a physical device for connecting pins to a DB9 socket. The white Mecer adapter is a plain old USB to RS232 adapter. The pins on my cat5 cable are wired to ethernet 568B on the battery side. So the mapping is: RJ45 Pin 3 -> RS232 TX+ RJ45 Pin 6 -> RS232 RX+ RJ45 Pin 8 -> RS232 GND I hope that helps. I haven't checked the ports on UP5000 vs US3000C, so maybe this useful info!

If you look at the SOC graph, you'll notice that my middle battery's SOC goes down slower than the other two. Could this be because the effective cable length is further for it?

Very interesting that you see the same with your middle battery. Also, I thought 5% was a low SOC to hit every day, but interesting to hear your SOH.

Here is a graph of my 3 batteries. They're all Pylontech UP5000, bought about 6 months apart. I'm curious why the yellow "battery 2" doesn't follow the others during the final charge phase. This pattern occurs every day as the batteries reach 100%. The weird thing is that yellow battery doesn't like to climb up the voltage curve with the other two. But only after they've hit 100% and dropped their voltages back down, then the yellow allows itself to climb back up again, and soon after that, all three are showing 100% SOC, and their voltages are back in sync until this same point, 24h later. That dip you see after nearly reaching 100% was just a 5kw load that drew on the batteries a bit, it doesn't have any relevance to the issue. The lowest I allow the pack to go is 25%, but I'm considering taking it down further once-off for calibration. Not sure how worried I need to be?

OK, that makes sense. I'm wondering now if the backup port gets phase locked to the gen port.

I've seen conflicting advice on whether to plug the generator into the Grid or Gen port, in an off-grid scenario. Which is better? The site is off-grid, with PV + Batteries + Generator.

@Skusku Did you ever get this working? I have a friend who's keen on hooking up a wind turbine to an off-grid Solis S6 and I'm wondering how best to incorporate it.

I'm considering using a 8-16S 200A JK BMS (https://cellsupplysa.co.za/products/8-16s-200a-jk-bms-w-communication-ports), and hooking it up to a Kodak MKS-IV (OGS 5.6). The inverter doesn't have any native "JK" battery type, but it does have support for Pylontech batteries. Can the JK BMS emulate other protocols, such as Pylontech?

Try setting it as high as it will go. If the range is 0..100 (or something like 5..100), then it's probably indicating SOC instead of voltage. These settings (i.e. the SBU/SUB switch) shouldn't be dangerous to play with, in the sense that you're not going to damage your battery, because you have the BMS cable attached. The BMS cable is what tells the inverter to stop charging once it's full. So go ahead and see the range of the setting. On my OG 6.2, the setting is definitely SOC. But on my OG 5.48, I never used this, because I ran my own control software. You can see the prices on Solar Assistant's website. It's $60 for the software. You can find raspberry pi on pishop.co.za.

Solar Assistant doesn't support Solis, at least according to their documentation/website. But probably worth contacting them to see if they're busy with it.

@Inverter You should consider using https://solar-assistant.io/. This will switch between SBU and SUB for you, and it has smarter control than the inverter's builtin functionality.

That's strange - I have no idea why it would do that. What are the limits of what you can set the voltage to? Do you have the BMS cable plugged in? What type of battery have you defined?

Hi @Inverter , if you've got the BMS cable connected, then the battery thresholds you are seeing might be SOC and not voltage. If they go up to 100, then it's probably SOC. SOC is what you want anyway, since voltage is just a vague proxy for SOC.

@Pho3niX90 I see, that does make it hard. I'm wondering whether it would work to predict the timing of the messages from the datalogger to the inverter. If one could accurately predict when the datalogger is talking, and the gaps in between those comms was large enough, then it might be possible to act as a master during the quiet times?

What about timing? It looks like my Solis Cloud data gets updated once every 5 minutes. That seems to leave ample time for another device to make some queries in between? To be clear - I have not plugged anything in yet, and I'm not even sure yet what device I'll use to talk to the RS485 (presumably some USB -> RS48 dongle). I'm just considering whether it's even worth it. @Sc00bs Regarding 5V vs 3.3V, that's something to think of. Are you implying that the datalogger's interface is electrically connected to the RS485 port? My datalogger (W2) plugs into a USB port, so I'd be surprised if this is a problem. But I'll keep it in mind!

Thanks @Moffat . I might just try and see what happens then.