Battery Relocation Dangers

[berjkara]

I’ve had my battery relocated into my trunk for 3 or so months now, and I have been hearing there are some dangers with the wire possibly fraying and causing a fire or things of that sort. I’ve heard I should put a fuse near the battery in the trunk just in case. Can anyone vouch for this? And if so, can anyone recommend what type of fuse i should get? Thanks.

 

-Berj Kara

[Son of Marty]

A well routed  and protected wire shouldn't fray but that being said sh*t happens and I also use a fuse. Marine supply stores carry high amp fuses and holder and that's where I got mine 250 amps is what I think I'm running but I would have to look to be sure, the picture is from west marine, carry a spare fuse in the glove box if you have one you'll never need it?

 

[John_in_VA]

If the wiring is running unprotected through sheet metal holes without grommets there could potentially be a problem - easily & cheaply solved.  Others will have to comment on fuse options.  Be careful!

[SydneyTii]

A few questions

What method did you use? 

TEP and wet battery?

TEP and AGM?

TEP and e30 cable?

e30 cable and battery box?

Cut off switch?

did you mechanically protect the cable by placing it in another tube?

how did you pass through the firewall and rear seat support panel, did you use grommets?

Are the battery terminals exposed in the trunk?

 

There has been posts on a fuse, I don’t think it would hurt.

 

Few pics would be good.

[Mike A]

Post some photos of the installation

[SydneyTii]

7 minutes ago, Son of Marty said:

A well routed  and protected wire shouldn't fray but that being said sh*t happens and I also use a fuse. Marine supply stores carry high amp fuses and holder and that's where I got mine 250 amps is what I think I'm running but I would have to look to be sure, the picture is from west marine, carry a spare fuse in the glove box if you have one you'll never need it?

 

Just be sure to rate the fuse accurately, too low and it will blow every time it loads up, too high and the cable will melt the insulation or worse before the fuse ruptures.

[Simeon]

1 hour ago, SydneyTii said:

Just be sure to rate the fuse accurately, too low and it will blow every time it loads up, too high and the cable will melt the insulation or worse before the fuse ruptures.

 

Absolutely. What size wire are you using? The fuse should be sized based on the current carrying capacity of the cable. 

 

Remember that the 100’s of amps the cable is sized for only happens as a peak when the starter motor kicks in. This is such a short duration it’s unlikely to worry a quality fuse. 

[jgerock]

West Marine sells excellent multi-strand insulated wire that is flexible and great for making battery cables. 

Edited March 28, 2019 by jgerock

[berjkara]

4 hours ago, SydneyTii said:

A few questions

What method did you use? 

TEP and wet battery?

TEP and AGM?

TEP and e30 cable?

e30 cable and battery box?

Cut off switch?

did you mechanically protect the cable by placing it in another tube?

how did you pass through the firewall and rear seat support panel, did you use grommets?

Are the battery terminals exposed in the trunk?

 

There has been posts on a fuse, I don’t think it would hurt.

 

Few pics would be good.

I am using a top end performance battery brace, the one that doubles as a strut bar. I have a positive terminal post that i have put in my engine bay to connect to the starter and other wires that need a positive connection. 

[berjkara]

and here is the thickness of my cable, for anyone wondering.

[Seth Horwitz]

Not to threadcrap, but what is the logic of a fuse? (Newbie question.) All positive connections are still tied into the same point, but there’s just an extra length of cable to where the positive terminal would be. Everything which has a fuse from the factory still has one. Is it just for fear of a chafed wire from a poor installation, or the risk of something loose in the trunk hitting the battery?

[M3M3]

1 hour ago, berjkara said:

I am using a top end performance battery brace, the one that doubles as a strut bar. I have a positive terminal post that i have put in my engine bay to connect to the starter and other wires that need a positive connection. 

Gas vent hose from battery exits the trunk under the car?

[Son of Marty]

Yes the Idea is to protect the main line as it runs through the car, a chafe through or getting a short in a accident would be the same as laying a wrench across the battery resulting in all hell breaking loose. 

[Simeon]

1 hour ago, berjkara said:

and here is the thickness of my cable, for anyone wondering.

 

A 4 AWG cable is rated for 120A not including any de-rating. I would use 120A as your fuse rating. 

 

32 minutes ago, Seth Horwitz said:

Not to threadcrap, but what is the logic of a fuse? (Newbie question.) All positive connections are still tied into the same point, but there’s just an extra length of cable to where the positive terminal would be. Everything which has a fuse from the factory still has one. Is it just for fear of a chafed wire from a poor installation, or the risk of something loose in the trunk hitting the battery?

 

Look at it like this. The risk of a major short goes up when you extend the length of your main battery cable and then run it through various panels from the rear to the front of your car. You have increased the ‘window of opportunity’ for a short significantly. This increased risk can be managed by making sure that your installation quality is good, you have used grommets, the cable is secured well and insulation is supplemented where necessary. You can (and should) do all this but belt and braces is good practice here and so a fuse or circuit breaker is easy to add. You should probably have one where the battery cable is the usual length too but we ignore that one as a risk of a major short is much lower. 

 

A cable of that size, running through your car would conduct enough current before the cable burnt through to explode your battery and set your car alight. This would not be a pleasant experience if you happened to be sitting in the car at the time. 

[Hans]

I'd  be covering those hot terminals in the photo car. Especially in the trunk.