Fuse or Circuit Breaker

[d2dave]

I have an auxiliary battery mounted at the rear of my D2.

From this battery I am going to run 6B&S cable to an Anderson plug at the rear bumper to charge the house batteries in my Tvan.

What is better to use, Maxi fuse or circuit breaker and the reason for your choice.

Also opinions as to size. I was thinking 100 amp.

[towe0609]

I'll be interested in the advice you get to this too. For interest, in a recent youtube video MOST PEOPLE GET THIS WRONG - YouTube (https://youtu.be/uxSUzi7PFk0), Ronny Dahl essentially said to preference fuses in engine bay due to heat, and circuit breakers elsewhere. I have no idea if the advice is based on any expertise.


I have an auxiliary battery mounted at the rear of my D2.

From this battery I am going to run 6B&S cable to an Anderson plug at the rear bumper to charge the house batteries in my Tvan.

What is better to use, Maxi fuse or circuit breaker and the reason for your choice.

Also opinions as to size. I was thinking 100 amp.

[Homestar]

I would use fuses myself for 2 reasons. Firstly is the heat issue under the bonnet. Circuit breakers rely on a thermal circuit that heats up as load increases and excess heat can cause early tripping. The other reason is vibration - eventually this will cause the breaker to nuisance trip - it’s one of the reasons we run HRC fuses in our gensets on pretty much all circuits, even low voltage, low current DC.

[Tins]

What Gav said.

As for rating, the cable you are using is rated to a max of 120. I'd prefer a little more margin than 24% but it's probably ample given good cable performs better than it's stated rating.

[scarry]

it’s one of the reasons we run HRC fuses in our gensets on pretty much all circuits, even low voltage, low current DC.

On another note,we have HRC fuses on many jobs as well,they are often near impossible to get hold of these days,particularly if they are needed urgently.

My two cents on what the OP asked,fuses any day.

[d2dave]

I would use fuses myself for 2 reasons. Firstly is the heat issue under the bonnet. Circuit breakers rely on a thermal circuit that heats up as load increases and excess heat can cause early tripping. The other reason is vibration - eventually this will cause the breaker to nuisance trip - it’s one of the reasons we run HRC fuses in our gensets on pretty much all circuits, even low voltage, low current DC.

Gav. Heat is not an issue here as the wiring is going from my battery in the rear of the vehicle to rear bumper.

However, in response to your heat concern with circuit breakers, I have one of Tim's Traxide isolators.

He told me that due to my battery being in the rear that I need a circuit breaker at each battery in case of a short between the two.

He sold me two 50 amp auto reset breakers with the isolator. They have been in use now for 10 plus years without a problem, one under the bonnet, one at the rear.

And when it comes to this stuff Tim is the man.

[drivesafe]

I have an auxiliary battery mounted at the rear of my D2.

From this battery I am going to run 6B&S cable to an Anderson plug at the rear bumper to charge the house batteries in my Tvan.

What is better to use, Maxi fuse or circuit breaker and the reason for your choice.

Also opinions as to size. I was thinking 100 amp.

Hi Dave and you can use circuit breakers or fuses and don’t take any notice of the idiot misinformation in that video.

I near burst out laughing when I heard him say “You should not use circuit breakers under the bonnet because of the heat, but fuses will work”.

Yes, in extreme heat situations, circuit breakers will go open circuit at lower currents.

BUT GUESS WHAT, fuses will act in the exact same manner. He has no idea what he is talking about.

Dave, if you use 6B&S cabling, while 6B&S is rated at a continuous current 140 amps in “OPEN AIR”.

But in the confines of a motor vehicle, 6B&S is derated to a continuous current rating of 105 amps.

Any fuse or circuit breaker use to protect a circuit must have a maximum current rate of at least 20% less than the cables continuous current rating, so an 80 amp fuse or circuit breaker would be perfect.

[drivesafe]

I would use fuses myself for 2 reasons. Firstly is the heat issue under the bonnet. Circuit breakers rely on a thermal circuit that heats up as load increases and excess heat can cause early tripping. The other reason is vibration - eventually this will cause the breaker to nuisance trip - it’s one of the reasons we run HRC fuses in our gensets on pretty much all circuits, even low voltage, low current DC.
Yep, fuses are far more tolerant to vibration.

[drivesafe]

I'll be interested in the advice you get to this too. For interest, in a recent youtube video MOST PEOPLE GET THIS WRONG - YouTube (https://youtu.be/uxSUzi7PFk0), Ronny Dahl essentially said to preference fuses in engine bay due to heat, and circuit breakers elsewhere. I have no idea if the advice is based on any expertise.

Hi towe0609, and sorry mate but that guy is nothing more than a keyboard cowboy.

There are so many erroneous statements in that video that people would be far better off ignoring just about everything he rants on about.

The most common bit of B/S that shows he knows nothing about batteries, is his claim that taking AGMs below 50% SoC can damage them.

Why would battery manufacturers specifically state that their AGM batteries can be discharged down to 20% SoC and some of the newer AGMs can be safely discharged down to 0% SoC?

Again, he calls the AUXILIARY battery a house battery.

For the forty plus years I have worked in the field, the second battery in any vehicle has always been called the Auxiliary battery and House batteries are found in Camper Trailers, Caravans and Motorhomes.

He as done a little bit of googling and is now making out he is some sort of expert in a field he actually hasn't got a clue about.

Again, he states the second battery under the bonnet should be a Deep Cycle battery and he claims it can used to jump start and assist when winching.

First off, most Deep Cycle batteries do not like under bonnet heat and they do not tolerate any form of ultra high current discharging.

There are heaps of other errors in his video.

[AK83]

I have both. In engine bay of the D1.
Both batts in engine bay. Aux has a 50A breaker, main has a 100A maxi.
Never triggered/tripped/blown.
Have accidentally hit neg to pos on the main a couple of times doing work, usually spanner(never learn!). Nothing tripped or blown.

I personally prefer a breaker simply for the quick and easy reset.
If there is a major issue and trips again, you don't end up blowing another fuse again .. just another reset. if happens again then figure out what/why, rectify, and away you go.

But with a fuse, if tripped a second time, do we really carry multiple 100A maxi fuses with us all the time, and where do you get one again easily enough .. especially when remote?

For d2dave, have you already installed an fuse/breaker to the aux battery? Is the question just related to how to fuse aux to the van?

[Tins]

Thanks Tim.... I nearly posted that vid here specifically to give you a laugh....

[jon3950]

He has no idea what he is talking about.

How can you say that, he’s Ronny Dahl - he’s an influencer.

[d2dave]

For d2dave, have you already installed an fuse/breaker to the aux battery? Is the question just related to how to fuse aux to the van?

Yep Aux battery was installed over 10 years with a 50 amp breaker at both ends.

This thread is about protecting my cable from aux battery to campers house batteries, via Anderson plug on rear bumper.

[RobMichelle]

Isn’t that what you catch when you drive with the window open ?

[TonyC]

Dave,
Ho much current do envisage the Tvan batteries drawing?

What cable is running from the cranking battery to the auxiliary battery?

I can't see the point of a 100 amp braker/fuse between the auxiliary batt and the Anderson plug when there is a 50 amp braker at the main batt, as all your current needs to pass through that 50 amp braker.

Can you connect you new cable to the non battery side of the rear circuit braker, rather than have a second one?

Tony

[JDNSW]

For my minor contribution - fuses are cheaper and probably more reliable - but you need to have replacements when you need them. And in a few years, these may not be as easy to find, especially in Woop-Woop!

Circuit breakers are much more convenient in use, but more expensive, and if it does need replacement, an exact replacement is not going to be readily available.

[Blknight.aus]

I do both, a resettable circuit breaker or self resetting if its a critical requirement thing with a bigger fuse.

so if you want a 100A load youd fit a 100A circuit breaker with a 120A fusible link between the breaker and the battery.

The logic.. if thecircuit breaks in the middle of no where shorting out, it trips the breaker. you find the damage, fix it and reset the breaker, and you can do this dozens of times if you need to (say you have an intermittant cable nick you cant find) if the breaker spot welds itself and you get the short, the fuse goes.

Remember if your doing it for a battery to battery connection you need circuit breakers and fuses at each end of the cable.

[drivesafe]

The suggestion of the 80 amp fuse, is to future-proof the setup.

The circuit breakers may last for ever, or need replacing at some time.

50 amp auto resetting circuit breakers can tolerate sporadic high current event that may trip them, but then they just cool down, reset and everything gets back to working and you will never be aware the system has tripped.

But a 50 amp fuse or manual resetting circuit breaker in the same type of event, will leave the setup open circuit until you discover the system has tripped.

So you need to replace an auto resetting circuit breaker with a higher current capacity fuse or manual resetting circuit breaker to reduce the chances of such event causing issues and with 6B&S cable, 80 amps is the highest safe current rating you can use.

[d2dave]

Dave,
Ho much current do envisage the Tvan batteries drawing?

What cable is running from the cranking battery to the auxiliary battery?

I can't see the point of a 100 amp braker/fuse between the auxiliary batt and the Anderson plug when there is a 50 amp braker at the main batt, as all your current needs to pass through that 50 amp braker.

Can you connect you new cable to the non battery side of the rear circuit braker, rather than have a second one?

Tony

A good point Tony. However, as I am running a fuse I am going for a fuse with a higher amps than the breakers. This way the breakers should protect the fuse.

The fuse will still protect the cable from aux battery to the Anderson plug and through to the house batteries.

And yes I could probably connect the cable between existing circuit breakers, but with the way it is set up this would involve a longer run of this very heavy cable and be more labor intensive.

And to answer your first question, batter to battery is 6 B&S, the same as I am running to my Anderson plug.

[Blknight.aus]

Dont forget to wire a telltale across the big fuses and the circuit breakers..

when one pops the light turns on.... I generally use 12v auto leds

If you use a decently sized light, in the event of a self resetting circuit breaker acting as a charge regulator it'll reduce the trip frequency and arcing.. IF you use it on a non self resetting circuit breaker it will still try to charge your battery, just very slowly, and your fidge or load will act funny. but importantly if you need it to run some critical LED area lighting you'll still get that to work.

[Redtail]

How can you say that, he’s Ronny Dahl - he’s an influencer.

And he spells it as influenza in his vid!
Makes me sick, too. [tonguewink]

Not to mention "daul batteries" in the opening titles.

[jon3950]

Not to mention "daul batteries" in the opening titles.

Don’t start me on the spelling, my inner Ron will come out.