Adding 2nd set of Pylontech Cables from US5000 to Multiplus-II

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David Molyneux asked Apr 22, '24

Adding 2nd set of Pylontech Cables from US5000 to Multiplus-II

I have had 2xUS5000 batteries connected to a Multiplus-II/48/5000/70-50 for the past 2 years and they have been running flawlessly. This week I added a 3rd US5000 and while refreshing my memory on the ESS settings I saw some posts about the supplied cables to the inverter not being large enough. Even at max output or when charging, the standard cables don't get remotely warm but I do have a spare set of the long cables and figured I should use use them if that would be better from a safety and performance perspective.

This is my setup now:

Would I just add the extra set to the spare poles top and bottom? Like this:

Thanks!

Multiplus-II Pylontech

pxl-20240420-201112304-2jpg.jpg (1.5 MiB)

pxl-20240420-201112304.jpg (1.5 MiB)

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Answer 1 · 2024-04-22T11:29:03Z

nickdb answered · Apr 22 at 11:29 AM

Fairly common to do that. Just need a busbar/lynx distributor to connect them to, don't whack them onto the same connection.

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Answer 2 · 2024-04-22T11:58:27Z

David Molyneux answered · Apr 22 at 11:58 AM

My intention was just to connect the 2nd set of pylontech cables to the inverter and then connect to the batteries, is this not feasible?

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nickdb ♦♦ commented · Apr 22 at 12:43 PM

It makes for a terrible connection. Terminals are not meant for stacking like that. Rather use a bus bar.

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David Molyneux nickdb ♦♦ commented · Apr 22 at 01:18 PM

So in this scenario I would need a Lynx distributor, thicker gauge cables from inverter to Lynx, a 3rd set of Pylontech long cables so each battery is connected separately and 3 mega fuses, one for each battery?

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nickdb ♦♦ David Molyneux commented · Apr 22 at 01:37 PM

No, you can use the loop method you have shown and connect the two sets of cables to a shared lynx or busbar. I would up the gauge on the feed to the multi to cater as well,

You could connect each battery individually, but probably overkill at this stage.

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David Molyneux nickdb ♦♦ commented · Apr 22 at 04:54 PM

Thanks, would 125A fuse be sufficient for each battery cable? I don't tend to see more than 4800w from the Multiplus when it's going flat out.

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Answer 3 · 2024-04-22T14:53:35Z

chrichri answered · Apr 22 at 02:53 PM

Hi, i did this already with two batteries. I had the cables left so I used them. These cables are only 25mm2 cables to my knowledge. I did exactly what you would like to do. In my case the two batteries are conected with the little cables. The second port of each - is conected to a GND Bus Bar. One screw per cable. The both + cables I conected stacked on a fuse screw (in my case its a 100Amp fuse - safe is better) and from the fuse with a 90mm2 cable to a main sewitch and then again with 90mm2 to the multi plus. This makes me sure not to loose any mV on cables :- )

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David Molyneux commented · Apr 22 at 04:56 PM

Do you have a picture? I can't quite visualise the fuse connector / distance from battery terminals etc.

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Answer 4 · 2024-04-23T06:34:51Z

dognose answered · Apr 23 at 06:34 AM

Adding a battery does not increase or decrease the overall current. It could, but not if the rest of the system stays the same.

Depending on the distance to the inverter, you'd be good with the 25mm cable i'd say.

People tend to exagerate cable sizes, because they use some "random minimum spezification" that works for all cable lengths and very often isnt required at all.

Properly fusing is more important than using arm-thick cabling ;-)

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Answer 5 · 2024-04-23T06:45:39Z

duivert answered · Apr 23 at 06:45 AM

just for info:

standard pylontech cable's are not 25mm2, they are awg 4 > 21mm2

the equivalent used in mm2 is 25mm2

never stack cable lugs, always use busbars, there are small ones available for that

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nickdb ♦♦ commented · Apr 23 at 07:27 AM

Yip, nothing sloppier and more amateur than stacking lugs. Also, both positive and negative should be fused.

Shortcuts eventually lead to problems.

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dognose nickdb ♦♦ commented · Apr 23 at 08:53 AM

more amateur than stacking lugs

I disagree with that ;)

If you are adding batteries for the sake of capacity, using vertical stacking is no problem.

If you add batteries for the sake of power, using horizontal stacking is the way to go.

It doesn't make sence to directly connect 12 Battery-Modules to a single busbar, when you only need a fraction of the possible output, but sheer capacity. It is more cost and space efficient to connect them as 3x4, if the discharge rate of 3 modules would satisfy the maximal required currents anyway.

Especially for installations "beyond amateur" levels, vertical stacking is widely spread to reduce costs and space consumption.

(sure, for 3 modules there is no reason to NOT use a busbar, but if the current of a single module(-stack) is sufficent there is also no reason to enforce it or considering either installation as "bad practice".)

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