question

Hi @OR, welcome to the Community!

If you're using proper high-strand DC cabling (not the mid-strand THHN or anything else, see the attached photo from a Victron manual for the correct wire type) then 10AWG (6mm2) will indeed fit, but you're correct - it's tight, and can be a hassle.

Some of the THHN and other incorrect types of wire in 10AWG won't fit at all, so check your wire type first, and then, if you do have the correct type, either grit your teeth and patiently work it in there, or simply go to 12AWG.

Thanks for this interesting information. According to the cable vendor, the max. diameter of a strand is 0,300mm, so it should be fine. So probably I have to thin out and use a smaller ferrule, not nice but I cannot afford to wait for another cable delivery. Then I will switch later.

Thanks.

You can solder the ends of the wire to keep strands in check.

Hi All,

I can confirm that it is NOT possible to professionally and correctly fit a 6mm2 cable into the PV terminals of the 75/15 MPPT Charge Controller.

Today I removed all the wiring from my panels and got underneath the MPPT where I could see properly.

There is considerable green plastic flashing on the terminal housing, and this is a push interference fit when using square crimped wire ends on a 4mm cable.

This green flashing snags on the crimp marks of the 4mm cable making inserting and removing possible but difficult.

This same flashing makes it impossible to insert a 6mm2 cable with a wire end ferrule fitted. It simply wont go past the green flashing on the terminal housing.

So, I trimmed the green flashing away, now a new problem arises.

The square crimped Legrand Brand wire end ferrule WILL NOT enter the slightly oblong hole of the green terminal block.

So removing the wire end ferrule and inserting the cable directly to the terminal is possible, but the fit to the terminal is so tight that it cannot be done without leaving some strands of wire hanging around.

So, this terminal block is at best a 4mm sq terminal block.

Sorry Victron, you have a manufacturing defect.

All the best,

Alex

PS: Yes, yes, I know I have invalidated my warranty by tampering with the device, and also possibly created a safety hazard.....

Super disappointing to read this....come on @Victron you need to get this sorted out as it makes you look totally unprofessional.

They have lovely documentation, talk lots about correct wire sizing and fusing in their wiring handbook YET they cheap out with these terminals.

At the risk of offending... And despite this being a 2 year old thread...

Why would anyone be using 6mm for 15A? I realise that for a long run you may want to increase cable size to minimise voltage drop but In those circumstances it would make sense to drop the incoming cable into a terminal box, or other device, and then take a 2.5 or a 4 from there. Provided you are in an enclosure of some sort, Tri Rated is fine and 2.5 Tri is good for 30A.

Given PV should be connected via fuses and an isolator the opportunity to reduce to 2.5 or 4 seems like a fairly straight forwards choice. My solar comes in on 25mm, and no there is not a chance that would fit into my charge controller.

Also; if a calibrated ferrule crimp tool, or even an imitation of one, is used you will find that the final form is in fact a rectangle. The round headed tools that produce a square profile result are not standard as far as I am aware. To be fair its a long time since I worked on anything that 'required' calibrated tools but I do not think the standard will have changed.

Sorry to be blunt but stuffing wires into holes is interpreted very differently around the globe and I also agree that a well designed rising, or spring, clamp terminal my actually be more secure without a ferrule. Personally I usually crimp everything up to 2.5 even if that means buying double ferrules.

Above 2.5 all bets are off, try looping a couple of crimped 10mm's in and out of a standard MCB or isolator! Sometimes, no crimp is the right crimp, especially if the tool is less than ideal.

I build and maintain Hydroelectric systems for a living and see too many horror stories to take this stuff lightly, sorry. Remember 15A at 75V is a little over 1kW which is a huge amount of heat in a small area if it all dissipates across a bad/poor termination/crimp

Hi Alistair, still learning so apologize if this is an incorrect observation.

If we take 12V nominal voltage, 15A to the battery over a one-way distance of 2.6m which due to installation limitations could happen would result in 6.122mm2 cross sectional with a 2% allowed voltage drop. So now one is trying to stuff 6mm2 wire in....

On the PV side you're right, unlikely 6mm2 would ever be needed.

So if I understood you correctly given everything has to be fused in/out, one would come out of the MPPT75/15 with a short piece of say 4mm2 and then after the fuse scale up to 6mm2 for example for the rest of the path to the battery?

Thanks Nick

There are some salient points in this thread in regards to solutions for this issue.

This however shouldn't be an issue to begin with.

When you reference a data sheet and it says that it accepts 6mm2 it is most unwelcome to discover it does not offer what is specified.

Hello from The Netherlands,

I was given 10mm2 cables to fit into the 75/15, obviously, it didn't work out well, although I did get them in there to some degree. 6mm2 cables did work for me.