Melted wiring at battery

[Sonniemacc]

Hi I’ve had a ‘slight’ problem with some leisure battery wiring. This wire runs from my starter battery via a fuse to my b2b charger, it’s 8AWG wire which I thought should be more than enough to carry the current (roughly 3m).

It looks like the wire has got so hot that it melted through the insulation and melted the battery casing. No idea how this has happened so would love some suggestions but my best guess is a bad connection of the ring connector to the terminal? Admittedly the connector wasn’t fit very well to the terminal and should really have been in its own threaded stud so maybe it was arcing?

It’s worth me adding this didn’t happen for over a year until recently I upgraded to a Lithium leisure battery which can be charged at 20A instead of the average 6A or so my Lead acid was being charged at. Perhaps this increase in current with the bad connection has resulted in this?

Any other thoughts?

 

[Howzat]

I'd also go with arcing but just make sure the b2b is deffo 20amp as 8AWG is only good up to 40amp. A cheapo clamp meter would confirm this.

 

[Dellmassive]

Poor connection with the wire and clamp at the battery.

Caused high resistance, and heat build up on the terminal and Worked it's was back.

Id replace the cable with a 16mm2 or 25mm2 cable.

Also where's the fuse?

 

[rippelep]

I had something similar, in my case the issue was the bad crimping, I got a smell fortunately and stopped the current.



it got hot in seconds.....

 

[Camper_Chris]

Hi I’ve had a ‘slight’ problem with some leisure battery wiring. This wire runs from my starter battery via a fuse to my b2b charger, it’s 8AWG wire which I thought should be more than enough to carry the current (roughly 3m).

It looks like the wire has got so hot that it melted through the insulation and melted the battery casing. No idea how this has happened so would love some suggestions but my best guess is a bad connection of the ring connector to the terminal? Admittedly the connector wasn’t fit very well to the terminal and should really have been in its own threaded stud so maybe it was arcing?

It’s worth me adding this didn’t happen for over a year until recently I upgraded to a Lithium leisure battery which can be charged at 20A instead of the average 6A or so my Lead acid was being charged at. Perhaps this increase in current with the bad connection has resulted in this?

Any other thoughts?View attachment 285406

This is typical of a high resistance connection, any resistance no matter how small contributes to the heating effect. There is a formula to demonstrate this effect. Power (watts) = current (amps) squared x resistance (ohms). So 20 amps squared is 400, if you have 2 ohms at your connection the heating effect is 800watts. Hence the damage you have seen. As an electrical engineer I see this issue time and time again, with poor connections, and people modifing wiring. You are just lucky you didn't end up having a fire and your van being destroyed.

 

[Dellmassive]

Hi I’ve had a ‘slight’ problem with some leisure battery wiring. This wire runs from my starter battery via a fuse to my b2b charger, it’s 8AWG wire which I thought should be more than enough to carry the current (roughly 3m).

It looks like the wire has got so hot that it melted through the insulation and melted the battery casing. No idea how this has happened so would love some suggestions but my best guess is a bad connection of the ring connector to the terminal? Admittedly the connector wasn’t fit very well to the terminal and should really have been in its own threaded stud so maybe it was arcing?

It’s worth me adding this didn’t happen for over a year until recently I upgraded to a Lithium leisure battery which can be charged at 20A instead of the average 6A or so my Lead acid was being charged at. Perhaps this increase in current with the bad connection has resulted in this?

Any other thoughts?View attachment 285406

What van is it?

Don't look like a T6?

Not that that matters

 

[Sonniemacc]

I'd also go with arcing but just make sure the b2b is deffo 20amp as 8AWG is only good up to 40amp. A cheapo clamp meter would confirm this.

It’s a Ctek d250se so maxes out at 20A but I also have a lithium battery with built in monitor so can see how much it’s being charged. Or could there still be more current drawn into the b2b charger even if not pushing out?

 

[Sonniemacc]

Poor connection with the wire and clamp at the battery.

Caused high resistance, and heat build up on the terminal and Worked it's was back.

Id replace the cable with a 16mm2 or 25mm2 cable.

Also where's the fuse?

The fuse is about 1ft after the terminal and I think like 30A but would need to check. I could replace the cable but not really wanting to as 8AWG should be more than enough for 20A plus it was a pain to route through :/

 

[Sonniemacc]

This is typical of a high resistance connection, any resistance no matter how small contributes to the heating effect. There is a formula to demonstrate this effect. Power (watts) = current (amps) squared x resistance (ohms). So 20 amps squared is 400, if you have 2 ohms at your connection the heating effect is 800watts. Hence the damage you have seen. As an electrical engineer I see this issue time and time again, with poor connections, and people modifing wiring. You are just lucky you didn't end up having a fire and your van being destroyed.

Yeah totally agree! It was fine for so long before but clearly the change of leisure battery and increase in current had a massive effect! I’m thinking of getting a new terminal like this one below for a better ring connection or I could wire directly in without a ring connector.

 

[Sonniemacc]

I had something similar, in my case the issue was the bad crimping, I got a smell fortunately and stopped the current.

View attachment 285416

it got hot in seconds.....
View attachment 285418

Yeah could be this! Is there way around this? Just better crimping?

 

[Dellmassive]

I wouldn't pull 20A over 10mm2 cable.... If defo up rate the cable to 16mm or 25mm

..

But 12v planet does show 8awg/10mm2 as ok on the volt drop calculator.....

For 20A at 12v on. 4meter cable run/one way.

.

 

[Dellmassive]

Yeah totally agree! It was fine for so long before but clearly the change of leisure battery and increase in current had a massive effect! I’m thinking of getting a new terminal like this one below for a better ring connection or I could wire directly in without a ring connector.

View attachment 285471

Don't use this type of connectors.

They aren't good enough.

You need a proper crimp on lug.

And a decent connection to the battery POS terminal.

Then use the chassis as the NEG return, and keep that neg cable as short as possible.