Battery in boot relocation questions

[crobaa]

Hi guys, looking to relocate my battery to the boot this week. I know this has been covered before but looking to 100% clarify a few things.

1. Do you need to run a negative wire from battery to engine bay? Or is it ok to run negative wire to chassis only, keeping in mind it's only a 1.5m longer cable run than factory.

2. What size cabling do I need to use to compensate for voltage drop?

3. If a negative wire needs to run, can it and the positive wire be run side by side the whole way or should they be separated?

4. Can I just purchase wire from supercheap or autobarn? If not, where?

5. What model of dry cell/sealed battery is suitable for b18c7 in eg hatch taking into account extra distance from motor. I'd like as small as possible without it becoming impractical, also where is the best place to purchase from?

Thanks

[mooshie]

just run the negative to a really good grounding point on the chassis, thats all they do in the engine bay anyhow.

Cabling size- bigger the better but at least 2 gauge, alot of people use welding cable which is about a 0 gauge as it is more flexible

good tool shops should be able to get welding cable and supercheap etc should be able to do 2 gauge

battery size is a good question I think about 350 CCA is standard on B18 cars? but I have heard of people running as low as 220CCA

Just remember to fuse the cable with about an 80A fuse close to the battery itself and use grommets wherever it goes through metal, I also wrapped mine in a cheap garden hose split along its length to give more insulation! also put corrugated tubing in areas where it could potentially rub on metal.

[crobaa]

Do you recommend using those firewall brass fittings that allow a lug to be bolted to either side? Or Just drill through and use a bush/grommet?

[Alexplicit]

just a caution, try your hardest to keep the positive away from the negative unless well insulated, just incast rubbing occurs

[crobaa]

Ok, I'll try space it apart where rubbing could occur, my main concern with them being close together was interference of emf of some sort but I doubt it would be an issue

[DLO01]

As a general, keep all cables as short as possible.

Run -ve straight to chassis. No need to run back to engine bay.

A larger gauge +ve is needed to compensate for extra length and therefore more voltage drop.

[crobaa]

What size ve would you recommend? Still looking for a battery model recommendation too

[Sexc86]

Gday mate,

Just been through a battery relocation myself.

Firstly i would run a 0gauge positive multistrand to your starter motor, then a 0gauge negative to a ground point in your boot (close to your battery). I would also run a secondary negative to your engine bay - 2/4 gauge (this will help minimise voltage drop over your chassis). Make sure you use high end double insulated multi-strand cable (not 7core or solid).
I would also highly recommend installing a inline circuit breaker between your battery and starter motor (dont waste your time with fuses - they are a nuisance - check out Jaycar electronics). If you are ever in a serious accident and your cable breaks and comes in direct contact with your chassis it can result in massive fault currents ! Also a circuit breaker can be another point of isolation to help keep your car secure from thieves (they cant hot wire the car if no power to starter motor and they dont know where the switch is ?)

Make sure you use a drycell like odyessey or similar securly mounted in a battery bin (check out battery world - Dont waste your time with supercheap)

[crobaa]

Is there any particular reason you chose zero gauge or did you just want to be safe? It's around 2 or 3 times larger than the standard cable right? Isn't it excessive? I see you're a sparky (I am too) so feel free to use jargon. Is the voltage drop formula in the cable selection guide relevant here?

[crobaa]

Just took a look at the odyssey website, the pc625 or pc680 seem to be good specs, what batt is everybody here using? The 680 is smaller, has less cca but weighs more. It must last longer? Is 220cca enough?

[Sexc86]

Is there any particular reason you chose zero gauge or did you just want to be safe? It's around 2 or 3 times larger than the standard cable right? Isn't it excessive? I see you're a sparky (I am too) so feel free to use jargon. Is the voltage drop formula in the cable selection guide relevant here?

Gday mate,
I chose 0 gauge just because the supply cable is alot longer when the battery is boot mounted compared to when when the battery is in its standard location - and even though you may only get a minimal voltage drop over the cable its still a relatively high percentage compared to the supply (being only 12v). Also i since the price in cable is minimal between sizes i simply chose to get the best. If you did decide to go 0gauge, you will need a 75mm ring lug (75mm cable entry with a 8mm - 12mm termination hole). However since the flexible cable compresses so much (more the our regular 7core). You will need to crimp it twice on two settings. Get some Hex multi-crimpers - First crimp on the 75mm settings, then go over your crimp again on the 50mm setting... its the only way i could get mine to hold ! (make sure you get 3 - 4 nice uniform crimps on your lug !) - Follow this up with some heat schrink on your lug to tidy it up and keep your exposed live parts to a minimal in your engine bay.

Also i mounted my cry cell in a battery bin in the boot and used some black compression glands for all the cable entries.... looks hella neat ;) ill try get you some photos in the next week .... i spent alot of time on my battery relocation

Good luck bro, any more questions just hit me up


Ps. The reason i would run a separate earth to your engine bay is that i have noticed in the past that some components use the chassis ground as a reference and some use the chassis ground to completely function (ie the circuit return path is through the chassis and not specifically a negative cable that is run to the device). So if you have a high resistance (common especially in older cars) over your chassis it can negatively effect how some of these devices perform. By running extra earth cables to different points over your chassis it will eleminate / reduce this.

[crobaa]

Thanks mate, I was planning on using the same glands you mentioned. Lucky I have a middys account lol. Was there any issues running zero gauge (fitting it through tight areas) I'm putting the batt between my rear strut brace and back seat on passenger side, was hoping to run the cable through the Chanel under the passenger door, under ecu and through firewall. Its good hondas mount battery on the firewall, like 1m less on cable to use compared with on the nose in most cars

[Sexc86]

Yeh mate, that was the only issue with large 0 gauge. Was a little tight in some spots but still manageable. Also remember to run a separate Positive feed for your fuse box which links up with your alternator. Or you could piggy back the fusebox feed from the termination point on your starter motor.

[crobaa]

Bump.

[DLO01]

What are you bumping? What else do you need to know?

[crobaa]

What battery to use, I've got no idea on what specs to look at other than cca

[Bludger]

the standard battery. (go to the shop and ask for a battery that suits your vehicle)

be careful of fuse selection. When you turn that key, you're unloading full power to that starter via the fuse,.

[Bludger]

Yeh mate, that was the only issue with large 0 gauge. Was a little tight in some spots but still manageable. Also remember to run a separate Positive feed for your fuse box which links up with your alternator. Or you could piggy back the fusebox feed from the termination point on your starter motor.depends how you do it, but if you just have the +ve running to the starter motor & leave all the existing wiring there, everything will work fine.

[crobaa]

From what I understand if the battery is mounted in the cabin or even in the boot it needs to be a dry cell so I cant use the standard battery.

[Bludger]

Do as you like, it seems you already know what battery you need, no need to ask.

I've had boot relocation's and only ever used standard batteries.

[crobaa]

I'm just clarifying the law. Let me know if I'm wrong but either way I'm not keen on breathing in any fumes coming out of a wet cell battery. Even mounted in a sealed box with a vent hose to outside I'd still rather a dry sell which as far as I can tell all odyssey batteries are. What I'd like to know is what odyssey battery to use

[xclusive_eg8]

where abouts are you mounting in the boot?? I got the wire, now all i need is time and a box

[crobaa]

Between strut brace and back seat. Less length on cable, less volt drop, and possibly better weight distribution too as opposed to further towards rear of car

[cotties]

oddessy pc680 is the best batt for its size
for a 5 second draw it will put out over 400 amps which you will never ever even come close to using, its just the nature of the agm dry cell, super high and fast current draw. this is why its hard to get cca ratings on them because they just dont behave like normal wet plate batteries.
4 guage is plenty big, dont know what everone else is saying, like you trying to start a truck motor or something. 4 guage cable is rated at like 120 amp continus draw so a 3 second start at like 60 amps at the most is a walk in the park.
as long as you use good quality cable you wont have any problems, audio power cable is pretty good just make sure its well protected in engine bay and from rubbing as the cable cover tends to be not as durable as proper battery cable.
the audio cable is also good cause they have a high strand count as you sparkys should know. the more strands, the more surface area, the more electrical current it can handle. its basic electrical theory. just the same case that 1.5mm flex is rated for the same amperage as standard 2.5mm twin and earth cause the flex has more strands and more surface area for the current to flow on.
also one good ground in the boot is more than enough, just make sure you sand down the area where the bolt is for best connection. as for ring termals easyest is standard gold plated audio terminals, just crimp them with proper battery lug crimper (not a hex crimper) or fold one side under the other with pliers or multigrips, then use a gas torch and add solder to the exposed cable on the ring side of the terminal, after that it will never come loose.
also dont forget to run the main power cable from the main battery point on the starter motor to the main fuse box in engine bay. for that 8 guage cable is fine.

[crobaa]

Thanks heaps mate, pq point given

[DA9-47]

hi guy's , i know this is an old thread, but any chance you could tell me if this wire is ok from Jaycar?
http://www.jaycar.com.au/productView.asp?ID=WH3094&form=CAT2&SUBCATID=995#1

and what type of circut breaker??
http://www.jaycar.com.au---------------/productResults.asp?whichpage=1&pagesize=10&keywords=circuit+breaker&form=KEYWORD (http://www.jaycar.com.au/productResults.asp?whichpage=1&pagesize=10&keywords=circuit+breaker&form=KEYWORD)

cheers

[crobaa]

Personally 0 gauge is overkill. You can use it if you like but it la harder to work with and more expensive. What's the c/b for? I would have thought oem short circuit protection is fine?

[trism]

You need 0 gauge to handle the current for the starter motor.

[Bludger]

you need a direct connection between the starter & battery, no circuit breaker will be able to handle the load....

Battery > master switch > >>>>>

-----starter
-----fuse/circuit breaker > rest of car.


meaning after the main switch, you may split it in two.....

one to the starter and one to the rest of the car, via a fuse...

[Bludger]

Personally 0 gauge is overkill. You can use it if you like but it la harder to work with and more expensive. What's the c/b for? I would have thought oem short circuit protection is fine?
not really......

[crobaa]

I actually spoke to an auto elec about this the other day. I'm an electrician too so I have an understanding of current carrying capacity of cables. But I'm just going off what he said. 0 gauge of course will work but you don't need such huge cable. My original batt location is next to firewall and planned location was right behind back seat on eg hatch so my volt drop would be less than most.

From an electricians perspective 0ga is so damn large and only used for pretty large applications. Not 1 or 2 seconds of start up current. Can anybody explain in further detail why 0ga is necessary?

[Bludger]

I actually spoke to an auto elec about this the other day. I'm an electrician too so I have an understanding of current carrying capacity of cables. But I'm just going off what he said. 0 gauge of course will work but you don't need such huge cable. My original batt location is next to firewall and planned location was right behind back seat on eg hatch so my volt drop would be less than most.

From an electricians perspective 0ga is so damn large and only used for pretty large applications. Not 1 or 2 seconds of start up current. Can anybody explain in further detail why 0ga is necessary?
I don't think anyone will dispute the fact with you that, smaller cable will work.
In all honesty, I think even 8Ga will do the job. Even twisting 3 or 4 figure8 together will work. (don't do it)

I'm disputing that you call it overkill. Because for the amount of money doing a PROPER battery relocation, $10 - $15 extra for the best cable isn't going to hurt.

[crobaa]

If smaller cable is totally adequate in every way then bigger cable is overkill IMO. Putting bigger cable would just be harder to run, terminate, hide and cost more for no gain at all. But I can see why some people just the biggest because they can

[Bludger]

we'll agree to disagree.....

agree?

[TbM]

I actually spoke to an auto elec about this the other day. I'm an electrician too so I have an understanding of current carrying capacity of cables. But I'm just going off what he said. 0 gauge of course will work but you don't need such huge cable. My original batt location is next to firewall and planned location was right behind back seat on eg hatch so my volt drop would be less than most.

From an electricians perspective 0ga is so damn large and only used for pretty large applications. Not 1 or 2 seconds of start up current. Can anybody explain in further detail why 0ga is necessary?

Most of the time you only need the starter for 1 or 2 seconds but in the off chance you have a fuel problem, ignition problem etc that requies you to crank the car over for a longer period than normal then your better off having the constant power handling that the higher gauge cables give expecially when your using longer lengths of cable.

Heres a chart i found that helps illustrate that when you increase the cable length and constant power handleing requirement of the wire, the required gauge goes up quite quickly.
http://www.hifisoundconnection.com/Shop/Control/fp/SFV/30046/view_page/Car-Audio-Wiring_Power-Wire_Speaker-Wire

[crobaa]

Agreed. Just realized I made this thread ages ago and still haven't done it lol. Damn being poor

[mooshie]

you need a direct connection between the starter & battery, no circuit breaker will be able to handle the load....

Battery > master switch > >>>>>

-----starter
-----fuse/circuit breaker > rest of car.


meaning after the main switch, you may split it in two.....

one to the starter and one to the rest of the car, via a fuse...

Not sure if I like the idea of an unprotected live cable running the length of my car....

I run an 80 amp fuse about 20cm from the positive terminal and in 4 years have not had a problem.

[Bludger]

There is the master switch.
What sort of fuse are you running.

[crobaa]

A hrc style fuse has a high start up load current and lower running current. Dunno if they exist for cars. What kind of amps does a starter motor draw? Just get a fuse that's bigger?

[crobaa]

Fault current will be way higher than whatever the starter draws

[Bludger]

If you must have one, look up a megafuse

[crobaa]

Most of the time you only need the starter for 1 or 2 seconds but in the off chance you have a fuel problem, ignition problem etc that requies you to crank the car over for a longer period than normal then your better off having the constant power handling that the higher gauge cables give expecially when your using longer lengths of cable.

Heres a chart i found that helps illustrate that when you increase the cable length and constant power handleing requirement of the wire, the required gauge goes up quite quickly.
http://www.hifisoundconnection.com/Shop/Control/fp/SFV/30046/view_page/Car-Audio-Wiring_Power-Wire_Speaker-Wire

That chart is for car audio am I right. That stuff runs for a long time, even with engine issues your only going to crank for 10 seconds or so, if it's not starting by then your gonna stop cranking and go fault finding or whatever. You would have to crank for like 30 seconds straight to start doing damage to the cable.

Another option in this scenario, which is way more obvious is that you run the firewall through terminals so u can just disconnect your batt and hook it up to those with jumper cables (which I might add are designed for break down situations, pretty long and still not zero gauge)

[DA9-47]

So basically most people's opinion are that i should just use 0 gauge wire even if it might be alittle harder to install , better overkill than underkill in my small noob brain lolz,

but with the Fuse, i think if someone would point me in the right dirrection with what sort of fuse i could use that would help heaps,

should it look like this? http://www.cloudelectric.com/product_p/fu-mega80.htm ???

[Bludger]

see post 41

[Bludger]

btw, thanks for the link

LOL

been looking where to buy them:p

[DA9-47]

see post 41
hmmm o k?

btw, thanks for the link

LOL

been looking where to buy them:p
so that is what they look like , ok now i understand, would jaycar have these ? maybe better than online, and having to wait lol

[DA9-47]

http://www.jaycar.com.au/productResults.asp?MID=1&SSUBID=658&SUBCATID=969&keyform=CAT2#1???

[Bludger]

the minimum fuse @ jaycar which is 125Amp is too large a value for egg/dc2/da

[Bludger]

mooshie said he runs 80a with no problem, 80amp sounds right to me.

[Bludger]

dear as ^*&#

http://www.keoghsmarine.com.au/product_list.php?g_CategoryID=37

[DA9-47]

the minimum fuse @ jaycar which is 125Amp is too large a value for egg/dc2/da
i need 80 Amp max>?

[Bludger]

I believe that constant cranking will blow an 80a mega fuse.

normal use will be ok i think.

[DA9-47]

I believe that constant cranking will blow an 80a mega fuse.

normal use will be ok i think.

so by saying that 100 Amp be better?

[Bludger]

no...

[DA9-47]

ok so constant cranking will blow an 80 Amp but a 100Amp is too much

[Bludger]

You want the one that will blow when pushed, not the one that will never blow....

If it never blows, why need a fuse?

[DA9-47]

You want the one that will blow when pushed, not the one that will never blow....

If it never blows, why need a fuse?

awesome cheers, that makes sence

have no idea about this stuff so thats why i ask silly questions

[crobaa]

Isn't the fuse purely for short circuit current? The amps being drawn by the starter should be pretty consistent

[trism]

The fuse is there to protect the cable in the case of short circuit.

0 gauge can run 150amps all day. But if there is a short circuit ie the insulation wears through and it grounds on the chassis, it'll flow infinite current. The wire heats up, melts the insulation, and causes it to catch fire, burning your car to the ground.

So we install a 140amp fuse. The starter wont draw this much, and if the cable does happen to short out, it'll pop the fuse instantly.

You have the fuse mounted with in 20cm of the battery, so that you only have 20cm of unprotected cable.

[crobaa]

The fuse is there to protect the cable in the case of short circuit.

0 gauge can run 150amps all day. But if there is a short circuit ie the insulation wears through and it grounds on the chassis, it'll flow infinite current. The wire heats up, melts the insulation, and causes it to catch fire, burning your car to the ground.

So we install a 140amp fuse. The starter wont draw this much, and if the cable does happen to short out, it'll pop the fuse instantly.

You have the fuse mounted with in 20cm of the battery, so that you only have 20cm of unprotected cable.

Exactly! All you need is a fuse larger than starter current

[DA9-47]

The fuse is there to protect the cable in the case of short circuit.

0 gauge can run 150amps all day. But if there is a short circuit ie the insulation wears through and it grounds on the chassis, it'll flow infinite current. The wire heats up, melts the insulation, and causes it to catch fire, burning your car to the ground.

So we install a 140amp fuse. The starter wont draw this much, and if the cable does happen to short out, it'll pop the fuse instantly.

You have the fuse mounted with in 20cm of the battery, so that you only have 20cm of unprotected cable.

wow that made the whole thing sound simple !!!thanks!!

just worried ill get the wrong fuse lol

how do i find out what a Da9's starter current is?

[mooshie]

Mine is a glass fuse in a holder but much bigger than the normal glass fuses for cars. I can't remember where I got it from now unfortunately..

[crobaa]

Maybe a car stereo type one?

[trism]

Yep. What you want is an "ANL" style fuse holder.