I have a solar system with 12 solar panels of 450W each, a Victron EasySolar-II 48/5000/70-50 MPPT 250/100 GX inverter, and a rack with 6 LifeP04 lithium batteries of 2.7 kWh each. The system is configured off-grid and was set up to discharge the batteries down to 35% charge or 50V, whichever comes first. At that point, it switches to using the grid to supply power to the loads and charge the batteries.
Everything worked well for about two and a half years (the system was installed in April 2022), but at the end of 2024, I noticed that the system started switching to the grid at around 28%, when initially it could discharge down to almost 10%. I contacted the installer, who said everything was fine with the system, but I insisted.
However, at this point, I have noticed that it is now switching to the grid at around 40%, meaning it doesnât even reach the previously set percentage, as the 50V threshold is reached before the pre-set percentage. My question is as follows: is this situation related to some calibration that needs to be done, or is it a case of battery degradation?
First, you should check all of the battery cable connections for tightness, any sign of corrosion, or local heating.
Depending on your daily discharge, battery operating temperature, and battery type, itâs possible that the capacity of the battery has diminished significantly. 2.5 years is ~912 days, so itâs a little surprising that you have significant capacity degradation (unless you cycle more than once per day). at 90% depth of discharge you should still be expecting ~2500 cycles. Check with the battery manufacturerâs data sheets for expected life and any warranty for early capacity loss.
I will attach some photos as it is easier for me, since my knowledge is very basic. The installation was carried out entirely by a specialised company and I just want to try to understand what might be going wrong so I can approach this company.
Photo 1 is from when the batteries were about 45% charged (information from Victron) and photo 2 is from about 2 minutes after charging started via the grid (I switched the grid circuit breaker on manually to prevent the system from shutting down).
The installer told me not to pay attention to what appears on these battery screens but rather to the information from the inverter, but I really notice that the second battery from the top has different values from the others â I donât know if that means anythingâŠ
The temperature in the room where the batteries are is probably around 20Âș Celsius at the moment.
The battery rack is connected directly to the Victron.
The batteries have a 10-year warranty, so I find it very strange that such a large degradation could have happened in such a short time, considering that on average, I must discharge about 50% of the charge per day (more in winter, of course, but less than that in summer).
I canât seem to find a CAN cable (like a RJ-45 Ethernet cable) so these appear to be so called âunmanaged batteriesâ. And then you are stuck with values from either the inverter or a shunt. Do you see a SmartShunt in your VRM (venus.local) ?
is VRM â Settings â DVCC enabled? If yes. What is the maximum charging voltage set to?
Yes, itâs true, the batteries have that small LCD with some information, and then the details about charge, voltage, etc., only appear on the inverter, without any auxiliary equipment.
I believe I mentioned the smartshunt to the installer, but he told me that the system, as it is currently configured, is more accurate than with that equipment and that they usually use it for smaller installations, such as caravans, etc.
I am attaching a screenshot of the information from Victron Connect with the default values for absorption and float. I remember that during the system configuration, the installer manually entered the battery bank data, with the respective capacities, voltages, etc.
The batteries are manufactured in Germany, if Iâm not mistaken, and the installer is an official Victron installer.
The system has been working perfectly since it was installed; the only issue that concerns me is the fact that the voltage and percentage readings of the batteries have been showing quite large discrepancies recently.
Seeing 0A on the second battery is concerning, and the current balance between the others is poor. This is one reason NOT to use batteries that donât communicate with each other or a central BMS management / reporting system. See Victron list of approved battery types.
I would check the power cables to the batteries for oxidation and tightness as a start. Also, you should fit a smart shunt to the system, inverter current and SOC measurement is generally poor, and your installer is wrong to advise you to trust that rather than the batteries internal BMS which should be more accurate.
If you have a 10 year warranty, and there is no cable issue for the 2nd battery, then itâs time to claim on that warranty.
Yeah there seems to be some kind of issue with the second battery from the top. The voltage seems to be in line with the others but there is data missing.
I did notice that the two top batteries report a higher capacity. Were these perhaps added at a later date?
What I would do is flip the miniature breaker at the back of the second battery, and see if that resolves the problem, and if it does â warranty claim!
Yes, 2 batteries were installed around 8 to 10 months after the installation of the solar system, which initially had only 4 batteries.
I believe the batteries were added to the lower part of the rack, because the first ones were installed at the top, but it could have happened that when these batteries were installed, the first 4 were moved down and the 2 new ones installed at the top â I canât quite rememberâŠ
I will have to speak to the installer, I just wanted to try to understand what might be happening before contacting him, so that when I report the situation, I can properly explain what is going on.
Is the âext resistanceâ on the display of the second battery always higher than the other batteries? It is rather hard to tell but it looks like a factor 10 higher.
Please check the cables of the second battery. Hopefully they cannot be moved were they are connected to the busbar.
Actually, this parameter has no values (----); itâs only when the batteries start charging that the value âshoots upâ to levels much higher than those of the other batteries.
The other parameter below always shows no values, even when the batteries are charging.
As for the parameters on the left (in the same positions as these), they are always at zero, but when the batteries start charging, they also begin to show values, but these are very different from the other batteries.
Regarding the cables, I donât want to tamper with them too much, but when I carefully pull the cables, they all seem well secured and I donât notice anything unusual about the connections.
