Pylontech US5000 drops charge rate after brief stints charging at high currents

[Umski]

Hello folks,

So as the seasons change I have a new annoyance - my other thread on the Solis RAI was getting rather lengthy and this is unrelated in a way so here we go.

The Solis and Pylon have been working great together over the last few months - surprisingly our leccy import halved over Dec and Jan - however as the days get longer I’m facing a new situation- when the PV starts to peak at 3kW or over on these cold windy days with intermittent cloud, the Solis takes the BMS value of 80A charge rate and happily dumps 3kW into the US5000 (the Solis is using the Pylon values so no custom values) - however the last couple of days the Pylon would then drop the charge rate to 0.2C which is 20A or roughly 1kW - I *think* it’s because the Pylon will only sustain short bursts at peak rates and so it drops it down to 20A for a period until it’s happy again - I guess this is temperature related but it doesn’t seem to decrease the discharge rate (I am seeing the values on the BMS info on the Solis) - my preference would be to just charge at a peak of 50A (or 0.5C) as would normally be recommended rather than these extremes - seems a bit of a strange way to program the BMS - wondering if anyone else with a single Pylon has experienced this?

I think there are a couple of ways to solve this

1. Use custom settings to limit charge to 50A or less but there are many more parameters which make me nervous - I am going to test this tomorrow to see if it will take the 50A continuously up to 80% SoC which is when I think it starts to ramp down the charge rate from the BMS

2. Add more capacity - a US2000B is reasonably priced as a small increase but the 4.8kWh of the US5000 have proven to me that my capacity was spot on as it’s worked with my current usage and over winter. Although it would be nice to add another 2.4kWh financially it doesn’t make sense for me at present

Thanks

[Tinbum]

This is for the earlier Pylon batteries and will probably be the same as the more modern ones.



Check DOD for the US2000B.

You can mix and match but personally I'd go for another US5000 when funds allow.

I'm not familiar with the Solis but check the CAN doesn't override any manual setting you put in for current. With my batteries the BMS normally only starts to ramp down in the 95+ (possibly 98+). Your battery may be getting over warm hence the reduction, it will be better for the battery life to limit the current. Have you watched the battery temp with BatteryView?

[nowty]

Add more capacity, a new US5000 has now dropped to £1,608.00 incl. VAT from ITS. As the days get longer you are only going to get more disappointed.

[Umski]

This is for the earlier Pylon batteries and will probably be the same as the more modern ones.



Check DOD for the US2000B.

You can mix and match but personally I'd go for another US5000 when funds allow.

I'm not familiar with the Solis but check the CAN doesn't override any manual setting you put in for current. With my batteries the BMS normally only starts to ramp down in the 95+ (possibly 98+). Your battery may be getting over warm hence the reduction, it will be better for the battery life to limit the current. Have you watched the battery temp with BatteryView?

Thanks, I have seen that table before but it doesn’t quite add up for the US5000 as the default values for C/D are 80A which equates to 0.8C - the lower values make sense as I’ve experienced those in the very cold weather in Dec/Jan - both C and D values then dropped to the 0.2 and 0.05 (20A and 5A respectively) but a quick blast with a 500W hairdryer soon got that up and once charging it went back to normal. I also sometimes see 50A and 60A values depending on what’s going on so I think the US5000 has more mapping than the smaller packs - hence the question for this particular arrangement.

Yes the simple answer is to add more capacity but at the moment any excess is diverted to my DHW anyway and I can’t justify the payback or losing out on a day’s free HW (without using gas) due to the extra capacity (though that’s not an issue later in the year) - the priority being the battery BUT if it does this current limitation then depending on the sun situation I miss the peaks for charging - I think in the grand scheme of things it’s not a biggie, just slightly annoying

I don’t have batteryview - I could do with looking into that to see if my hunch is right - the BMS doesn’t seem to report it to the Solis it seems

[Tinbum]

I don’t have batteryview - I could do with looking into that to see if my hunch is right - the BMS doesn’t seem to report it to the Solis it seems

The BMS does report it in its CAN messages to the inverter. I don't know if the inverter uses it for anything though. 0x356 bytes 4 and 5.

[Umski]

I don’t have batteryview - I could do with looking into that to see if my hunch is right - the BMS doesn’t seem to report it to the Solis it seems

The BMS does report it in its CAN messages to the inverter. I don't know if the inverter uses it for anything though. 0x356 bytes 4 and 5.

Thanks, that’s useful to know - I know of some other Solis AC and hybrid users on another forum so will check with them too - I know I’m not on the latest firmware for my model but as it’s been working okay the faff of going through Solis service hasn’t warranted it - yet!