question

jonofe avatar image
jonofe asked

Victron Distributor Torque is deforming Mega Fuse

Hi Guys,

I'm currentlich installing a Victron ESS based on MP II 5k and Pylontech US5000 with Lynx Distributor.

I'm using Mega Fuses in the Distributor, but when using the recommended Torque of 14 Nm, the Mega Fuses are deforming. I fear, that I will destroy them.

Please have a look at the 125A fuse:

megafuse.jpg

How can that happen?

Order of mounting from bottom to top:

Megafuse => DC cable => washer => lock washer => nut

is it due to poor quality of the fuses (~30€ per fuse)?
Wrong order of components?
Should I add additional washers?

I'm a bit lost, why this happens with such expensive components!

Any help is very much appreciated!

BR, André

lynx distributormegafuse
megafuse.jpg (3.0 MiB)
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

8 Answers
Alexandra avatar image
Alexandra answered ·

@jonofe

That is probably because the torque is 10nm at least on the fuse side. I usually do 10/12nm both sides. Depends on the feel.

[Edit: I did see the 14nm reference]

Are you sure you have not twisted the bolt in the plastic housing at the bottom?

An face the fuses the other way so the window shows you if they are blown or not.


2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

jonofe avatar image
jonofe answered ·

10 Nm is only for the nut below the fuse. The top nut should be 14 Nm.

What do you mean with twisted the bolt? I did not open the plastic housing below, because the Distributor has all bolds in place.

I checked it again and finally I saw, that one side of the fuse was completely teared, so its really broken. It seems that also the cable lug is moving, when fastening the nut with 14 Nm and the cable forwards the presure to the fuse. So I don't know what going wrong here. How can I check, wether I have original victron fuses?

Summary: I have still no idea how to avoid damaging the fuse if I don't reduce the torque.

Any hint, where to buy mega fuses in Germany which have good quality?

1 comment
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Alexandra avatar image Alexandra ♦ commented ·
I would have the fuse on top of the lug when using the lynx, then the washer -spring washer -nut.

It is weird how you have the twisting moment there.


0 Likes 0 ·
daza avatar image
daza answered ·

I’ve used the Littelfuse‘s and torqued to 14Nm on a distro no issues I do make sure to holed the cable when I’m actually torquing it down though So the cable does not move.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Mike Dorsett avatar image
Mike Dorsett answered ·

Correct mechanical practice where a lock or retaining nut is torqued to a higher value than the nut below is to use a second spanner on the lower nut. This is better than holding the cable, which would place a strain on the crimp.

2 comments
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

seb71 avatar image seb71 commented ·
From the picture it looks like the lug and the fuse blade rotated while tightening the nut. Holding the lower nut would not prevent that. Best would be to hold the lug somehow.
1 Like 1 ·
daza avatar image daza seb71 commented ·
By cable I do mean lug didn’t think it would be taken as cable literally. Thought it would be apparent as for holding the lower nut that should not spin at all the flex all comes from the top of the lug is held it won’t twist at all, do them hand tight with normal socket making sure the lug is straight then the nip up with the torque wrench securely holding the lug that fuse won’t move as long as that lug is on top and the lug is securely held in place.
0 Likes 0 ·
seb71 avatar image
seb71 answered ·

What type of torque wrench did you use? Click type? If click type, did you stop right when it clicked?

What is the torque range?

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

nesswill avatar image
nesswill answered ·

This could happen if there is a burr on a washer causing the washers to lock and putting the twisting action on the lug and in turn on the fuse causing it to move.

Are the washers new or have they been used?

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

jonofe avatar image
jonofe answered ·

The washer were brand new and came with the distributor.

Meanwhile I ordered other Megafuses (same specs) and 5€ instead of 30€ and there is no problem at all. They are much more massive and seems they can resist the torque power.

I uses a Click torque wrench (scale 8 - 25 Nm) and set it a bit below 14Nm. And yes, the lug is moving and subsequently the fuse as well, but I already tried to hold the cable.

My only concern now is the quality of the new mega fuses. How can it be, that there is a difference of 500% in price (5€ vs. 30€)? At least from stability perspective, the cheaper ones are better. :)

1 comment
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Alexandra avatar image Alexandra ♦ commented ·
@jonofe

Try ordering the lugs and fuse differenly.

Even the little red lug in the top bus bar place that on top of the fuse rather than under it.

1 Like 1 ·
daza avatar image
daza answered ·

@jonofe the fuse sounds questionable for a 58volt mega fuse, only fuses I know that are that cheap are the Littelfuse but they are rated upto 70volts if it is the littelfuse don’t worry it’s all good and they don’t seem to have inherited the absorbent fees of the Mega!

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

Related Resources