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