question

Hi @krouink

I'd run with the recommended 70mm2 for the Multis, and the maker's supplied cables. Some of those are special cables with high temperature insulation and should suffice to a common busbar.

However, what this suggests is that you haven't enough batteries. 10kWh isn't much for 15kVA of Multi. You don't say the brand, but Victron usually list the recommended number for those they document. And using less may actually void the battery warranty.. https://www.victronenergy.com/live/battery_compatibility:start

You could run each battery to the bus bar twice and not interconnect the batteries to each other.

JohnC brings up a good point: make sure your batteries are capable of the peak current needed by the Multis. This of course depends on your loads and charging limits.

Hello @JohnC , hello @Kevin Windrem ,

thanks for your answers. I like your idea Kevin to run each battery to the bus bar twice, assuming the batteries don't mind it (they are supplied with miniature link cables to interconnect in a stack rather than go to a bus bar twice).

The batteries are what Victron would consider 3rd party (not listed) LiFePO4, look a bit similar to the Pylontech ones. I wanted to start out with the 10kWh as I have them already (warranty is less of a concern) hoping I could manage by setting up limits?

I understood it is a bad idea to add batteries from another manufacturer to the bus bar (mix and match). Also in the future the hope is that the large battery from an EV can be hooked up.

Do you think with a small battery the Multis won't run smoothly? It's important to know that bulk of solar power is on AC side and one aim is that the Multis allow for 3-phase operation in the event of grid failure.

Hi Guys,

I stay shortly before cabeling my 3 Pylontech US5000 to a Lynx Distributor and a 3 phase Multiplus II 48/5000 system. This is the first step and I plan to expand it later to 6 or 9 batteries.

Unfortunately I couldn't find any serious cabeling plans and tables, showing appropriate dimensions for connecting the batteries to bus bars. If a US2000 has a charging current of about 25 A, the US 3000 of 37 A and the US5000 of 80 A, cabeling is not an easy task ! Especially while Pylontech shows diagramms, where 8 batteries were parallel connected. This means a charching current of 640 A for 8 x US5000 connected via a 25mm2 cable !

I've checked the cabel of the connectors of Pylontech 2000/3000/5000 series and they are all the same size, a 5.3 mm Amphenol Connector which takes 16mm2 or max. 25 mm2 cabels and no 35 mm2 or above. This would require a 8 mm Connector.

Therfore I plan to connect each of my US5000 batteries via two 25mm2 cabels directly to the bus bar. Parallel connecting more than one batteriy, as Pylontech recommends, will override all current limits for a 25mm2 cable (US5000) ! I can not understand, why this cabeling should be allowed and safe unless the BMS will never allow that the max loading/unloading current is higher than 80 / 100 A. If this limit is not controlled and there is no fuse inside of the red line, this would be a very dangerous installation site !

But the 25 mm2 connection is good for 80 A (max 100 A) and if each battery has a separate cabel for Plus and Ground to the bus bar. Additionally I will install a fuse of 125 A on the outgoing red cable and also a breaker for each battery.

The connection to the Multiplus II can also be 25mm2, secured by a 125 A fuse (no breaker required).

Each cable (Plus) leaving the bus bar must be secured ! No exception !

The terminals on the Lynx and Multiplus II allow also wider cabels like 35mm2 or 50 mm2. But they are not really necessary, because the Multiplus II is limited to a 70 A charge/discharge current and this is inside of the limits of a 25mm2 cable (< 2 m).

Please give me any comments for corrections or hints to my plans, so that I can proceed !

Thank you for your help and advice !

Bernhard