US5000 with Busbar

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daza asked May 1, '23

US5000 with Busbar

Hi I’m looking at going a Busbar route for connected 2 possibly three US5000 Pylontec batteries, what I aim to do is have a neg and pos bus bar wired in parallel would that setup be ok load balancing/charging.

The issue that I have is I can only get 125amp mega fuses aim is to fuse each battery separately but that 125amp is above the max amps that the manufacture states. The recommended Amps is 80amps per battery but seen as I’m theatrically splitting it per battery 125amp safety fuse is too much? Not so clued up on DC side as much as AC. Advise please

busbar

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alaskannoob commented · Sep 20, 2023 at 05:02 AM

If you are wiring each battery to the bus bar, does that mean you are not using the short positive and negative cables to connect batteries to each other?

I am setting mine up and have them each wired to the bus bar and have not used the short cables to wire them to each other, relying on the bus for them to be parallel connected.

But from what I understand, the batteries can balance amongst each other. I'm not sure if those small power cables are then required for that to work. Any idea?

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Answer 1 · 2023-05-01T04:10:03Z

kevgermany answered · May 01, 2023 at 04:10 AM

From memory, the 80A figure is a recommendation for max continuous load, with 100A being allowed. With much more for shorter periods.

The BMS in the batteries will stop excessive current.

The fuses are to protect the wires.

You should design the system so that you don't overload the batteries.

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Answer 2 · 2023-05-01T06:07:58Z

daza answered · May 01, 2023 at 06:07 AM

Hi thanks ok so the fuses will be good then, the Inverter is going to be a 48/5000 multiplus2 I did read some where to set it 25amps per battery, I’ll be using it on power assist from grid and solar so the battery under load won’t be beaten up. Thanks again. From the inverter to the bar ill be using 70mm not more than 2metres in length and then using the supplied pylontech cables to the fused bus bar. Do you think I should use a bigger diameter cable than 70mm?

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Answer 3 · 2023-09-20T13:33:49Z

Craig Chamberlain answered · Sep 20, 2023 at 01:33 PM

Firstly I agree 100% with what was said above that the 125A mega fuses are to protect the cables not enforce the 80A max recommend operational current. You definitely don't want your fuses blowing when running at nominal current levels. As said, the BMS in the Pylontech will manage the current draw and will alarm and/or shut down if you exceed limits.

I'd say 70mm cables are absolutely fine and are what I myself am using on the same inverter with the same batteries. I have three US5000 batteries all connected in parallel to my (modified) Lynx Power-In with 125A megafuses. I then have a second Power-In also modified with fuses added to provide the feeds to the inverter (200A) and my two MPPTs (80A each).

Having originally went with a pair of generic bus bars and fuse holders, I would strongly suggest considering the Lynx Power-In or Distributor as it is much better solution overall and actually not as expensive as it appears when you consider what you get for your money. (ie. 2 x 1000A bus bars, 4 x fuse holders, nice enclosure etc). I got mine for £140 each. You can also get mega fuses rated for 48V operation (actually 70V max) from Mouser if you need ratings that Victron can't provide.

HTH

Edit: I just realised this was an old thread resurrected by a new comment. Oh well, I'll leave my response in case it helps. :)

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