Other inverters, like Fimer, have manual that state the minimum and maximum conductor size that you are allowed to install in the wire terminal blocks.
For the MultiPlus II 48 4K5 I was looking for similar information. I can’t find it in the manual (pmp48205012…). On page 16 that only states:
DC cables should be copper, with a 90ºC (194ºF) rating.
And there is a table with blank fields for battery capacity, DC fuse and core conductor areas.
I can understand the need for specifying copper conductors (galvanic corrosion).
From “Wiring unlimited” I’ve understood that Victron terminals only like fine stranded wire, solid conductors will come loose over time in the used terminals.
But why is there the Multiplus DC cable 90 ºC (194 ºCF) cable rating limitation? (With corresponding larger conductors and thus lower operating temperatures, I don’t see the problem in using 60 ºC rated rubber cables.)
I don’t see the problem either, but with high amps, you should keep the temperature low. To do this, dimension the cables a bit larger. Some people put all the cables together in a trunk, sometimes even a metal one. If the cables get too hot and the insulation melts, you can get some small sparks.
It is referencing the rating of insulation of the cable chosen. This (90°C) is a common rating for solar installations. Some cables are rated differently and are designed for lighter or heavier use and environmental factors.
So if you look more at data sheets for cables you will see 60°, 75° or 90° etc.
As an example not related to battery cables - pv need to be higher as roof temps can or will be higher.
Because I’d rather prefer an IEC 60332-3 70ºC rated cable with 0.2 mm copper fibres over IEC 60332-1 90ºC rated cable with class 6 diameter 0.3 mm copper fibres.
I don’t want Victron Energy to limit my MultiPlus DC-bus cable choices with minimum 90 ºC rated insulation.
I do not ever want to reach a core temperature of 90º C. For an LFP battery cable my upper design limit is 50 ºC core. (cable heating will also heat the cells).
If you have dimensioned the cable correctly you should not be seeing that heat there at all. Especially not that much heat. So, if it is going to be in trunking in your install use a higher gauge than shown in the manual as it is rated for open air at that dimension.
It gives some insight into what was used by Victron conductors serves as a general design guideline to ensure reliable performance under a wide range of conditions. They assume responsibility for verifying compliance with applicable standards
However, where you the system designer has a thorough understanding of the installation environment and associated thermal limits, alternative cable types may be selected. In your case you are familiar with standards and your install specifics and are taking responsibility for it and will be checking it to keep it safe.
The Rev 00 (04/2025) Dutch MultiPlus II 4K5 manual uses a stronger wording then “should”. My translation from Dutch to English:
DC cables must be copper and operate at 90 ºC (194 ºF).
Must for copper is not a problem. The must for the 90ºC rating is a problem.
There is at least is a translation incoherence between the Dutch and English language versions of the MultiPlus 4K5 manual.
I could live with “DC cables must be copper and should operate at 90 ºC (194 ºF).” This leaves room for the system designer regarding cable temperature rating. The current Dutch language version doesn’t give that room.
Strange Victron Energy manuals. The current Dutch manual, still Rev 00 04/2025, no longer contains the 90 ºC DC cable limitation in section 8.2 (currently that sections is page 14). Why doesn’t update Victron the manual revision number when the text changes?
It would be great if the website resources page/tab, includes the document revision, at least for manuals and datasheets.
At the end of the day Victron can only say what they used in their set up to produce expected results. Complying to Local Regulations will always be the higher authority on any install.
As an installer your duty is to make sure compliance and safety is met.