question

reinobert avatar image
reinobert asked

3-phase multiplus II 5kvA dESS and Pylontech cabling question

Hello Victron hive mind,

Long time reader and now first time poster.
I am in the process of learning and designing my own (d)ESS storage system and I have a question regarding how to connect Pylontech US5000 batteries. I am also keeping in mind that my system should also be able to run the house incase the grid fails.
So I am planning 3-phase system with 3x Multiplus 2 5KvA, in total it may produce 3x 4000W, so 12kW. There will also be 1x RS450/100 MPPT. For now I am planning 6x Pylontech US5000 in "single stack" parallel, but here I think I might have a big problem. Let me know if I am overthinking this.

  1. In the pylontech's manual it states that the power cables are only rated to 100A, which is only 4800W (48Vx100A). If all the phases are maxed out, I will blow the fuse for the 100A cable.
  2. I have also seen in the Pylontech's manual that you can use 2 pairs of power cables, this brings the amps to 200A (9600W). Still short of 12kW. Is it that simple? Won't this bring a possible imbalance in the stack however?
  3. The solution I am thinking of now is to create 3 stacks of 2 paralleled batteries. This way i get 3x 100A, which totals to 14.4kW. This should make sure I don't send more than 100A over the 3 power cable pairs. It should max out at 84A only this way.
  4. My "solution" at bullit 3 brings me to the next problem (yes, i love it). If the entire system is connected to a 48V lynx busbar system, I again have the problem that I create an possible imbalance in the system? Especially since the idea is that it will use the Pylontechs with the dESS, so they will be heavily used. Which only worsens the possible imbalance.

screenshot-20241.png

My feeling is that I have a bigger chance of an imbalance of creating 3 stacks of 2 Pylon's than one big stack.

Am I overthinking this? Is there a more simple solution to my "problem"?

Big thanks and regards.

Multiplus-IIPylontech3 phase
2 |3000

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1 Answer
Alexandra avatar image
Alexandra answered ·

@Reinobert

Overthinking.

Pairs of pylons will be fine. Their OG cables are rated to 120A. Alternate them as in the picture. Your cables will get warm. (I would personally have each battery up to the bar have more than one lynx, it is a waste of energy when heat is made like that.)

The lynx is short so imbalance is less of na issue as the paths are close in length. Pylons sort their own soc as individuals anyway. You will get imbalances anyway even with individual connections, each battery has its own internal resistance difference.

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