And this, dear children, is why you NEED a torque wrench and a thermal imager!!

[Crossy]

This was in the first battery pack I built and at the time I didn't own a torque wrench.

I did notice the MCB getting a "bit warm" on the thermal so I ordered a new one.

But only when it arrived did I pull the pack!!

It didn't seem to be "that warm" but it would seem that it was.

 

 

 

 

 

 

[Muhendis]

Many years ago I also got involved in clamping up electrical connectors.

Admittedly we aren't talking of multicore copper cable, but the rules are probably the same.

We were designing the copper busbars for an electroplating plant in South Korea.

The copper busbars were somewhere in the order of 200mm x 15mm. These were the small ones inside the transformer cabinets.

The busbars needed to be bolted together with six bolts at each joint. We were to ensure that the bolts were not done up too tight.

Copper has a bit of elasticity which is lost if the pressure is too great. This elasticity is important when taking into account temperature changes.

As copper cools, it gets smaller so an overtightened joint becomes looser. This looseness gets taken up by the natural elasticity if the joint is done to the right torque

so the correct amount of tightness is important.

It pays to check yer nuts periodically.

 

[lom]

I'm not a big fan of breakers within a battery case and also not a big fan of small DIN mounted double width DC breakers when it comes to higher current. All my battery packs/stacks use only the external wall mounted bigger MCCB type breakers which have a bigger connection surface and a bigger M6 bolt.

[Crossy]

Yeah ^^^, if another one goes fzzt I may replace it with a length of wire and add an external MCCB with nice solid 8mm screw terminals and lugs.

 

Individual pack current rarely exceeds 60A, so I suspect it really was an inadequately torqued terminal.

[BritManToo]

I've got one like that going to my battery as well.

Melted the cable, but the MCB just about survived.

I love the smell of burning plastic in the morning.

[MangoKorat]

Got me worried now.  Did an underground cable joint on my UK household incomer (post meter) and can't remember if I retightened the allen screws after bending the cables into line so the joint covers aligned and clicked into place. 

 

Had a similar problem previously, not my doing though - the electricity provider made a bad joint onto the main cable when the house was built.  15 years on I turned on the microwave one morning and lost all power - been a little flickering for a week or so prior to that. Provider arrived and found the burned out joint.

 

Still, house is sold and I'm heading for Thailand soon 🙂.

[Crossy]

Remember a few years back a whole row of cottages in Wales blew up?

 

Turned out to be an open supply neutral (bad joint) and the whole return current was going via a conveniently earthed GAS PIPE with a predictable result.

[Pogust]

Had a similar experience lately. The inverter suddenly stopped connecting to the batteries. Didn't start a firework though as it was the terminal connecting the DC fuse to batteries that the producer forgot to tighten properly. Now I should have checked the other side of the fuse when I connected to the battery side I guess...

 

Interesting on overtightening Muhendis, I'm always careful on AC connections as the frequency can create vibrations and cause the bolts to come loose. Different on DC it seems.

[MangoKorat]

22 hours ago, Crossy said:

Remember a few years back a whole row of cottages in Wales blew up?

 

Turned out to be an open supply neutral (bad joint) and the whole return current was going via a conveniently earthed GAS PIPE with a predictable result.

Thankfully there is no gas in my village 😁

[Yellowtail]

"It didn't seem to be "that warm" but it would seem that it was."

 

I love that...