I'm having a problem problem with my system. Most mornings it stop charging my battery after about an hour or two. The battery SOC is then only about 50%.

Rebooting the inverter usually helps but it is not always practical so I'm looking for a permanent solution. 

My system:

1 x RCT-Axpert 5K inverter  (see attached liable) 

6 x 250watt panels 

1 x US3000C PylonTech battery 

Settings:

02 - 20a

05 - usr

12 - 48v

26 - 52.4

27 - 51.8

Firmware - 73.00e

I would really appreciate any suggestions to get this resolved. 

 

 

Edited January 4, 20223 yr by TheOracle

11 hours ago, TheOracle said:

Firmware - 73.00

Update to patched firmware version 73.00e. It fixes the premature float problem, where a passing cloud makes the inverter-charger think that the battery is full because it's not drawing much current. It also has some other goodies like KettleKomp™, though to benefit from that you have to read the instructions and set that up properly.

I assume from the age of the inverter (about the same as mine) that the 250 W panes are 60 cell, and you have them wired 3S2P. But if they are 72-cell, it may be panicking due to excess panel voltage if you have them wired like that. You can check a data page on the front panel to see if that's your issue. The PV voltage should be ≤ 115 V most of the time, to be in the MPPT range. Anything over 130 V and the output will start to derate, anything over 145 V and the SCC will shut off (but could still be damaged because it doesn't disconnect from the panels).

Your system would benefit from another US3000 module, subject to finances of course. You could then also increase the maximum charge current (setting 02) to 60 A, though your 4 panels will rarely put out more than 30 A on the battery side. Having that setting higher may make the inverter-charger better able to transition to the float stage; it uses the value of setting 02 to determine when the battery is full.

Thanks for the detailed reply Coulomb. Unfortunately I have already applied the patch about a year ago. 

Yes my system is old and the panels are 60 cell, but I will monitor the PV voltage to see if something funny is going on. 

I do have 6 panels, so I will increase the maximum charge current and see if it helps. 

I only use about 35A during the night, so I don't really need another battery. I will consider it if there are other benefits. 

Edited January 4, 20223 yr by TheOracle

20 hours ago, TheOracle said:

Settings:

26 - 52.4

27 - 51.8

it looks to me set too low, it could behave that way when batteries are (partly) full. Also disable battery equalization (33).

My 2 Axpert/Synerji MKS 5K work fine with settings (26) 54V, (27) 52.5 to 53V.

20 minutes ago, Beat said:

it looks to me set too low, it could behave that way when batteries are (partly) full. Also disable battery equalization (33).

My 2 Axpert/Synerji MKS 5K work fine with settings (26) 54V, (27) 52.5 to 53V.

Thanks for your input. 

I received those recommended settings when I replaced my old batteries. Please see this thread: 

 

 

2 hours ago, Beat said:

23 hours ago, TheOracle said:

Settings:

26 - 52.4

it looks to me set too low,

It's slightly low, he had it at 52.5 which is the "forum gold standard", as a suggestion to avoid some possible overshooting. But it would not cause the battery to stop charging at 50% SOC, I would not think.

8 hours ago, TheOracle said:

I have already applied the patch about a year ago. 

Ah. Then your firmware is 73.00e, not 73.00 as you said. That threw me off. Sorry, I find it hard to keep track of all the people I talk to on these forums.

So what voltage does the battery get to when it finishes charging? According to the inverter (front panel or monitoring software) and multimeter at the battery preferably.

Perhaps you have voltage drops on your cables. Putting setting 26 back to 52.5 V may help slightly with this. Are your battery cables at least 35 mm²? Though with a maximum charge current of just 20 A, I would not expect this to be a problem, unless they're really thin (like 4 mm² or something).

My apologies about the firmware version, I should have been more clear. 

Will monitor the battery voltage tomorrow and give feedback. 

My battery cables are the standard once which came with the PylonTech battery. 

Thank again for your help, Coulomb! 

I have changed setting 26 to 52.5, and the Axpert behave must better now. 

My Axpert is misbehaving again. 

It only charges to 89% and then after a while the battery voltage go very high and the solar panels disconnect. 

Here is my current settings:

I did upgrade my battery firmware recently:

 

4 hours ago, TheOracle said:

It only charges to 89%

Is that coming from the inverter (via monitoring software) or from the battery's BMS (via monitoring software or something that talks directly to the BMS)?

If it's coming from the inverter, it is fairly meaningless.

4 hours ago, TheOracle said:

after a while the battery voltage go very high and the solar panels disconnect. 

That's really weird. You are only charging from solar, and the solar goes away... and the battery voltage goes high! It looks to me that the battery is disconnecting for some unknown reason. The inverter isn't designed for this (some later models are), so the "battery" voltage (voltage at the battery terminals of the inverter) goes wild.

Then the battery decides to connect again, but now its voltage is quite low (perhaps 49.5 V, or about 3.33 V per cell, which is the resting voltage of LFP cells when not charging or discharging for some time). After a minute or two, the solar charger starts charging again.

Is it possible that when the inverter thinks that the battery volage is bouncing around near 51.5 V that it's actually much higher? Yet the voltage is so flat, it's like the LFP cells are nowhere near fully charged. They might indeed be at 89% SoC.

Perhaps there is a cell that is much fuller than the others, and its voltage rockets to about 3.6 V at this overall SoC. That could cause the battery to disconnect. But I'd expect the battery to give some sort of warning, or you should at last be able to find something in logs. Sorry, I know nothing about Pylontech batteries, other than the 48 V models are 15S LFP.

Especially considering the recent battery firmware update, I'd concentrate on the battery side for now.

@Coulomb  there might also be the possibility that the SCC voltage regulation is not functioning as it should be . I would like to suggest that @TheOracle performs the same charging cycle but with the PV input disconnected and the grid charger enabled .  I infer from the solarassistant graphs that the BMS went into protection mode and as a result the SCC charge voltage went up to 57V for about 7 minutes before the machine was restarted. That's not what I am used to in terms of the Axpert battery voltage regulation. I have in many occasions booted the Axpert with a 52V  bench supply with a blocking diode , and I still get stable regulation from the grid charger. I expect the SCC charger to match this stability.

On 2024/06/14 at 6:09 PM, BritishRacingGreen said:

I infer from the solarassistant graphs that the BMS went into protection mode and as a result the SCC charge voltage went up to 57V for about 7 minutes before the machine was restarted.

Good point. For example, the buck transistor (at least one of them) could have shorted. I was thinking that it shot up to 57 V too quickly for that, though. But maybe there was such a short, bringing the voltage up to say 54.5 V, and the BMS decided it had enough of that and disconnected, and that sent the inverter's "battery" voltage to 57 V.

I was also thinking that the battery voltage was jumping around a little too much. Maybe one of the SCC transistors was shorting intermittently, just for seconds at a time, and only when the SoC reaches about 89% does this cause the battery voltage to trigger the BMS to disconnect.

Quote

That's not what I am used to in terms of the Axpert battery voltage regulation.

Yes. Overshooting the target voltage that suddenly and that far is not typical Axpert solar charger behaviour.

Thanks for everyones input, I really appreciate it!

I think I fixed the issue! I added this  Tuya smart breaker to my electrical panel last week, but it turns out that was the culprit. Once I disconnected it, everything went back to normal.

@Coulomb, my apologies I only saw your post now. I have my Solar Assist connect to the inverter and PylonTech battery so I assume the soc is from the battery. 

Again thank for your input. 

I spoke to early, it happened again today except the soc went to 98%

I have to switch off the inverter for the voltage to go back to normal. 

Edited June 15, 2024Jun 15 by TheOracle

My battery cells seem to be in balance 

@TheOracle

Hi, were you able to solve the problem of the max charge at 89%?
The same thing happens to me and I have not found any solutions.
Thanks

Edited November 7, 2024Nov 7 by RobyT

@TheOracle,

"My battery cells seem to be in balance"

SA can only tell you the highest/lowest battery cell voltage at the time when you are observing the screen.

This, in my opinion, is a "flaw", in that you don't really see what happens to the cell voltages difference over a full days cycle of charging/discharging. 

You SA may show a small 13 mV difference, but unfortunately one needs to look broader.

I see @Youda has posted an program to do this, assuming it's windows based, then you can monitor you Pylon's cells. Not sure if the program has graphing facilities, as the BMS Tools I use, also doesn't give one the ability to graph the cell voltages over say 24h.

In the time I was using SA, I saw different values at different times of the day, and I don't have the time (who has?) to constantly monitor SA. Even so, SA could "catch" an errant value, but no indication of which cell is misbehaving.  

I capture my battery voltages using Influxdb & graph it with Grafana. With such a graph, one can see the problematic cells. As my batteries are getting towards 3 years old, I watch them regularly, to see if my 3 misbehaving cells are deteriorating any further. They have been consistent over the last 6 months, since getting this to work. 

At least I would know which cells I need to replace, if one or more goes belly up...

38 minutes ago, RobyT said:

@TheOracle

Hi, were you able to solve the problem of the max charge at 89%?
The same thing happens to me and I have not found any solutions.
Thanks

Yes, the issue was related to a Tuya smart breaker I added.