Battery relocation...

4th February 2016, 01:01

Wasn't really sure where to post this, I can't post in the motorsport section for some reason, so.

Right, just to be sure before I go ahead and do it, as I've read many different things and seen people arguing over what's the best way.

Am I okay going from the battery to the fuse box, and then branching off the fuse box to the starter and smaller fuse box? I've read of people suggesting junction boxes but it just adds more clutter to do the exact same job.

Also, I'm guessing 25mm square 170a cable is what I'm after, and then to stick a 100a fuse inline?

Thanks.

4th February 2016, 16:36

Quote:

Originally Posted by BSA

Wasn't really sure where to post this, I can't post in the motorsport section for some reason, so.

Right, just to be sure before I go ahead and do it, as I've read many different things and seen people arguing over what's the best way.

Am I okay going from the battery to the fuse box, and then branching off the fuse box to the starter and smaller fuse box? I've read of people suggesting junction boxes but it just adds more clutter to do the exact same job.

Also, I'm guessing 25mm square 170a cable is what I'm after, and then to stick a 100a fuse inline?

Thanks.

Where u getting all your cables etc from mate as I need to do mine.

4th February 2016, 18:20

Quote:

Originally Posted by ldavies

Where u getting all your cables etc from mate as I need to do mine.

Probably eBay mate

5th February 2016, 08:37

first thing -- you cannot have a fuse in main power lead
your starter could take 300amp spikes when starting .
simplest way is to run main power lead from battery direct to starte motor --then all other wiring can stay the same
--but do not skimp on wire quality as the further way the battery is the more voltage drop you get .
more strands and bigger the diameter the better -- solder all connections

5th February 2016, 08:47

You can have a fuse in the main power lead indeed.

You have to look for how long it draws that value,let's say it could draw 300 amp on a start up but you'll only see that value from a few milli-seconds wheres the fuse needs that for several SECONDS to break.
Refer to the fuse technical sheet.

5th February 2016, 13:46

so why do no car makers fit them on main battery lead ?
cos it don,t work and what would it be protecting if on main supply --only the battery lead--so pointless--have multiple large fuses once you split up the power to go to different parts of car --but never on main lead

5th February 2016, 16:21

When the battery is in an engine bay you wouldn't need a fuse due to it being very close to the applications it needs to be connected to.

However when in the boot it is a good idea to put a fuse as close as possible to the battery to protect the meters of cable that run trough the cockpit.it would cut the supply in case of any spark avoid any possible fire.

8th February 2016, 08:33

sorry you are just wrong --even on diesel trucks vehicles with single or mulitple batteries half way down the chassis --they sill don,t fit fuses --
more connections means more resistance and voltage drop -- --just not needed at any time
I am not arguing you couldn,t find a fuse to suit -- but just not needed or wanted

even fitting a isoltator switch increase voltage drop ----unless very high quality

8th February 2016, 12:43

Quote:

Originally Posted by VeiRoN

When the battery is in an engine bay you wouldn't need a fuse due to it being very close to the applications it needs to be connected to.

However when in the boot it is a good idea to put a fuse as close as possible to the battery to protect the meters of cable that run trough the cockpit.it would cut the supply in case of any spark avoid any possible fire.

I dont understand. Where is the reasoning in this?

8th February 2016, 16:34

Voltage drop is another matter,we're just discussing the fuse part.

I agree with you that most of the time you don't need a fuse but that one time that somehow the positive wire is allowed to make contact with a chassis part that's where you'd have hoped you had one.
This is the way I've done it personally,obliviously you can do it the way you think it works best for you and assume your responsibilities.

8th February 2016, 16:39

Quote:

Originally Posted by Stissy

I don’t understand. Where is the reasoning in this?

What are you referring to specifically?

8th February 2016, 17:05

Quote:

Originally Posted by axsaxoman

more strands and bigger the diameter the better

That's a little vague,you have to consider what's the biggest current draw you have (which should be your starter motor) and the distance from the battery to the junction box (if you used one),keeping in mind these a 25mm2 170amp cable worked for me (battery in the boot)

You can refer to this table (orange is cable's length,yellow AWG size)

Quote:

Originally Posted by axsaxoman

simplest way is to run main power lead from battery direct to starter motor --then all other wiring can stay the same

If you run the main lead from battery to starter motor and all of the other wiring stay the same how would you power up the smaller fuse box? From what I remember if you don't want to use a junction box you still need to run a positive from the starter motor to the fuse box.

Quote:

Originally Posted by ldavies

Where u getting all your cables etc from mate as I need to do mine.

I've replied with links of the material you need in your thread you've made about battery relocation but seems to have gone unnoticed.

Quote:

Originally Posted by axsaxoman

so why do no car makers fit them on main battery lead ?

I know of cars that have fuses on the battery main lead for the same reasons I wrote about,that's where my thoughts are based from.

8th February 2016, 21:10

BMWs are often a good source of good quality battery cable. E34 5 series has the battery under the rear seat and the cable might as well go three times around the car for the amount of wire there is in there. Obviously don't get it from a car that's been wet so the cable is all green and crappy. You have to pull all the carpet out but the quality of the wire is worth the effort. Only by buying known good quality wire from an old-fashioned welding supplies place (where they are likely to care about quality) will you find cable of similar quality.

Personally, I don't solder any joints because it 'wicks' up the wire and where it stops it becomes brittle. You're not allowed to solder wire joints in aircraft for this reason. I use proper crimps but it is expensive for the proper tools. If you don't have proper tools them crimp as best you can and then just 'seal' the end of the wire with a quick flash of solder, and to do this you need a seriously big soldering iron (like 500 watts). If you don't have access to a very big iron or proper crimps get someone to do the crimps for you who has, once you've got the lengths sorted.

I've been in the car job close to forty years and I've never seen a fuse in a starter cable. Run the cable inside the car making sure it's adequately fastened down and not rubbing on anything and it will be fine.

Don't use shit Chinese wire, come to think, don't use shit Chinese anything.

If you haven't bought a battery yet, have you considered getting a Lithium one to save a good few kg? Magnetti Marelli do them now for very sensible money.

25th March 2016, 02:11

Thanks for the information Chip. I'll see if I can find a E34 in a scrappy. Otherwise I'll just get some new decent quality cable.

Interesting point about soldering, I never knew that. Handy to know as otherwise I would have soldered it lol!

I'll give those Magnetti Marelli lithium batteries a little research. I was going to go for a lightweight gel battery like those sold for kit cars.

My other question is am I okay going from the battery to the fuse box, and then branching off the fuse box to the starter and smaller fuse box? Otherwise, what kind of junction box am I going to be after? Thanks.

25th March 2016, 10:15

Quote:
Originally Posted by axsaxoman View Post
so why do no car makers fit them on main battery lead ?
I know of cars that have fuses on the battery main lead for the same reasons I wrote about,that's where my thoughts are based from.

please tell me what make and model of car you have seen fuse in main power lead --like wayne i,ve been at cars for 45+ years and never seen a fuse in MAIN lead

maxi fuses --60 -80 amp for rest of systems but not in starter circuit

mercs also have batteries in boot --so thats another source in the scrappy --cable looks like welding cable on a big stick welder its that big