Hello everyone
I have a question:
I have 8 Pylontech US2000C batteries, in parallel with a Multiplus 2 GX Victron 5000/48.
When retrieving the battery information (via the RS232 port), I notice that when the multiplus indicates 100% charge, all the batteries are charged at 100%, but in the morning for example, when the multiplus indicates 33%, I have a battery that is at 16% and others at 53%.
The average is indeed 33%.
Can you tell me if this is normal? If not, how can we fix it?
Thanks in advance
Are they in one stack of 8?
Are they all the same age?
Are you using both +'ve and -'ve connections (one top of stack, one bottom of stack)?
I would consider having more stacks with fewer batteries.and connecting them via busbar.
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Yes they are stacked, and the + wire goes from the battery at the top, and the minus from the battery at the bottom.
The 2 at the top are 4 months newer than the others.
Currently I have for example:
Pack SOC 42.0% 59.0% 77.0% 69.0% 48.0% 57.0% 59.0% 58.0%.
its better to keep the stack smaller and parallel them 2x4 or even 2x2
Also pylontech forbids to stack them liked this on top off each other, you could violate your warranty
Ok, but how do you make the connections with for example: 2x4, or 2x2 ?
You will need more pylontech cable connection sets, 2x4:
From the victron pylontech manual
https://www.victronenergy.com/live/battery_compatibility:pylontech_phantom
With such an assembly, do I have to modify the configuration of the multiplus?
Nope keep it as is
you only might need a busbar if you dont already have one
Ok, I’ll make the change.
While I’m waiting to make the change, can I swap it with another battery, even if it’s the first (master)?
or is it not recommended?
Also make you absorption time MUCH longer, and set absorption voltage == charge voltage
Stick to the documented settings. If installed correctly there is no need to deviate.
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But there is always some room for experiments, hard to hurt the batteries…
I’ve experienced several stacks where single batteries would shut off because of overvoltage in one cell, after some time balancing would correct the error and the current went up again. If absorption is too low and too short the balancing can’t work…
When changed, keep the system charged for a few days
Even better would be to charge them individually and whent they are all at 100% soc connected them and let them balance out over a couple of days
Weak packs usually end up with high SOC, since the BMS prevents discharging cause one or more cells would get under voltage.
Those packs with low SOC are usually ok.
Inspect the 77% pack an do a capacity test. I bet this one has weak cells.