Circuit Breakers & Temps - TOMZN overheating

[nate_syd]

any sign of over heat/melting ?

oh sorry - nah 100% perfect
The cable is also a lot larger too - so somewhat of an unfair comparison.
Old stuff was equiv to the BMS cable (2x7AWG I think) - new stuff is much, much larger.

 

[summit]

oh sorry - nah 100% perfect
The cable is also a lot larger too - so somewhat of an unfair comparison.
Old stuff was equiv to the BMS cable (2x7AWG I think) - new stuff is much, much larger.

i was wondering if the overheating at the breaker had transfer sufficient heat back to damage the welding cable insulation, not so much due to resistive heating by current flow.

 

[nate_syd]

i was wondering if the overheating at the breaker had transfer sufficient heat back to damage the welding cable insulation, not so much due to resistive heating by current flow.

The previous cabling - yes, it was rated at 125deg & did suffer. The middle of the cable in open air was fine, but at the ends it had been deformed slightly.

 

[nate_syd]

Thinking about all this - what's interesting is that at the other end of the damaged cable above - it was perfectly fine.
I think a *significant* portion of the issue is the clamping/fixing of the cable. When it was put in the breaker - the cable gets screwed down, you're just not going to have a large amount of surface area. At the other end its a crimped lug - cold welded on the cable & large lug surface area = no issues/heating. Look at the ZJBeny breaker - only accepts lugs.

IMO - i'd probably say that anything over 60-80A should only ever use a crimped lug. There shouldnt be such a thing as a screw onto a cable setup above that current.
Maybe it would be ok if its not sustained... but safety & headroom IMO.

 

[JRH]

Under load what is the voltage drop across the breaker?

I have found that most electrical products that are imported from Asia have ratings that are based on unrealistic assumptions. They tend to use minimum size wire, flimsy connectors and fasteners of dubious quality and metallurgy. However if you know this and avoid operating at the top end of their rating they can work fine.

Different philosophy of engineering at work over there. Here in the US most engineers calculate the minimum necessary and double and triple it for safety. Over there they calculate the minimum necessary and than try to find a cheaper way to barely reach it.

The only thing I intentionally buy from China is YumYum Sauce or Soy Sauce… they can keep their cheap prices and cheapo products…

 

[pmknowles]

There was an earler question about how they were wired. These DC breakers are supposed to be wired battery at the top (unlike AC breakers where the input is at the bottom). Not sure if that would be the issue...

 

[Ron-ski]

These DC breakers are supposed to be wired battery at the top

Directional and polarised breakers shouldn't be used on a battery, current flows both ways with a battery.

Read the guide here, see the section that's titled "Directional or Polarized DC Breakers – Don’t use ‘em", although that's talking about using them on individual strings in parallel, the same clearly applies to batteries especially as the current flows in both directions - charging and discharging.