Outer Limits 4x4 Board

Hi all,

I have a question regarding this type of circuit breaker


Do these operate with current travelling in either direction? They are marked with a positive terminal and negative terminal. Reason for this is that I have a 2nd battery in the back and want to have a breaker at each end so that if the cable were to break half way then the spare battery wouldn't cause a fire if the cable were to short circuit (this is opposed to having a breaker at only one end).

Hi stuee, sure their note marked “BAT” next to the short stud and “AUX” next to the long stud.

Away, they are not polarised, in other words they do not have to be fitted in one specific direction.

They have a short stud for the battery side because there is usually only one cable to be connected on that side while on the other side there is a long stud so that you can connect a number of cables to it.

So in your case, you can fit them any way that suits you.

Cheers Drive Safe,

I just picked this unit up when I saw it in Jaycar while picking up some distribution blocks. Got a plus and minus sign but different length studs like you say. I was just concerned that perhaps the breaker mechanism might only work in one direction as I have no idea how these particular breakers work.

If in doubt bench test it and let us know, Better to be safe

pongo wrote:If in doubt bench test it and let us know, Better to be safe

Unfortunately I don't have any equipment that can suck up over 50 amps. I guess I could always try shorting the lead but that's a bit dodgy.

I'm happy with drive safes opinion at present.

Hi stuee, I’d be a little cautious of anything bought from Jaycar unless it was specifically labelled as being intended for automotive use.

This may be the reason for the strange stud markings.

See if there is some info about the device on their web site because while the quality of the product is not in question, how it performs could be.

There is a specific paten for how an automotive circuit breaker must work but circuit breakers made for other uses may not ( and in most cases do not ) perform in a way that is suitable for automotive use. It might mean that your 50 amp CB will perform more like a 20 amp automotive CB.

This may sound strange but there are some very big differences in the way CBs operate. A CB intended for use in a sound system may trip if the applied current exceeds the marked CB maximum by just 10% while an automotive CB is designed to tolerate up to 45% above the marked maximum for 1 hour.

This shouldn’t be a major problem other than it may trip every time a high current load is switched on, like driving lights or your fridge motor and so on.

The CB part number was labeled as being an automotive 12v CB.

Mind you that's not to say that they haven't been mixed up with others or placed there incorrectly. I'll look into it. Worst case I'll take it back. Still a while of putting the battery in anyway.

Hi stuee and this may sound like nothing more than splitting hairs but if it’s a genuine AUTOMOTIVE circuit breaker, it shouldn’t have 12 volts marked on it because Automotive circuit breakers can be use in 6v, 12v and 24v vehicles.

That one just may be the way the Chinese mark them but it’s not common to have the voltage marked on them and it should not matter what voltage they are use with, the current rating is the same, I just have come across voltage specific automotive circuit breakers.

Well I took the easy option, took the jaycar unit back and found one marked with the batt and aux. All good now