I have a solar system, with 12 PV, a Victron inverter, an MPPT and
8 batteries in parallel. They are Pylontech US2000C.
I monitor the status of these batteries with the MultiSibControl software (equivalent to Batteryview)
And I notice that at the end of the night, the charges of my batteries are very variable: especially the first one which is very low compared to the others
Pack SOC 22.0% 35.0% 52.0% 46.0% 33.0% 37.0% 39.0% 35.0%
The inverter gives me 37% (average of the values above)
What do you advise me?
Can I swap the batteries? For example replace the first one with the third or fourth?
Or do you think the first battery has a problem?
You should also know that they all go up to 100% when there has been sun all day.
Or you could change the wiring.
If you have used the daisy chained set up for the whole stack and taken the wiring off the first one, that is the problem.
In short you have poor current sharing. See here
Indeed, only bad wiring, nothing else, daisy wiring as Pylontech does is a proven fact already for years not to do so.
Up to packs of 3, maximum 4, ok, but more than that you have exactly this issue.
Buy an extra set of cables with lugs and “split” your bats and connect it 2x4 to the inverter or busbar.
Issue solved.
What you are seeing is the result of a long period of multiple partial chargings, right?
Don’t worry. You will be okay.
The Pylontech firmware knows to properly balance the loads and the current sharing when all are interconnected.
It’s one of the roles of the discharging FET.
When one of the batteries reach a too low SOC, you’ll see that the corresponding battery’s current will drop and allow others to take over.
This, up to a point, regardless of cable’s improper sizing.
This is not hearsay, it’s a fact found out from studying their firmware.
Yes, of course, trying to switch units never hurts.
The “Weakest” in the middle and the “strongest” on the edges.
And indeed, Alex is correct, the software will try to balance the units, but, as can be seen, it doesn’t do a great deal with so many in parallel.
Specially at higher currents these units start to divide from each other, as can be seen above.
Also, when 2-3 units are “empty” and you start a big load then only 5-6 units have to take that load, not nice, as lithium does not like high currents, and so making those units very quickly “older” than the rest.
While charging it works normally perfect, as that is of course the real “job” for the build-in BMSs, discharging is not.