Battery to boot - what do I need?

-westy- · 28 Jan 2008 at 18:53

Right, I want to move the battery into the boot of my 205, just to free up some space and shift some weight about. A few questions:

Is it just a case of using a distribution block to extend the battery cables through the bulkhead, under the carpet and into the boot?
What kind of cable would I need?
Is there any particular way to run the cables under the carpet? I've got my ICE cables under there too, should they be avoided?
How do I go about storing the battery in the boot? Sealed plastic box with a breather, then all clamped down?

I'm a bit of a noob when it comes to car electrics to be honest, (not that you could've guessed or anything..)

Thanks

paradigm · 28 Jan 2008 at 18:56

When you say "cables", I assume you just mean "cable". You only need to run the positive back to a terminal block under the bonnet. Negative can just be bolted straight to the bodywork in the boot

I'd run the ICE down one side of the car, and power down the other, to avoid interference on the speaker lines.

-westy- · 28 Jan 2008 at 18:58

Oh, can it? result. I've got a plate in my engine bay that holds all the earths, What do I do with that? And where do I put the negative lead from my battery?

paradigm · 28 Jan 2008 at 19:00

So long as the plate under the bonnet that joins all the earths is connected to the bodywork at some point (could use your negative battery cable to connect to the body in the engine bay), then the circuit will be complete so long as you get a decent connection from the negative terminal of the battery to the boot floor/arch/similar.

Not sure what guage of wire you need, been a while since I did any work involving recabling car batteries.

Firestar_3x · 28 Jan 2008 at 19:02

4 Awg at a guess?

paradigm · 28 Jan 2008 at 19:07

Sounds about right.

-westy- · 29 Jan 2008 at 00:51

So I can just run the negative battery cable to an earthing point in the engine bay, and sort myself a proper earth to run from the negative battery terminal in the boot?

Means I can take my amp cabling out too, just run a short one from the amp to the battery - Can the earth from my amp and the battery share an earthing point in the boot?

agw_01 · 29 Jan 2008 at 01:31

Use a rear seatbelt mounting point for the battery earth. Thin metal will run the risk of overheating and possibly melting.

Use an absolute minimum of 4 gauge cabling and fuse it at the battery end. I'm using a 150 amp fuse and 2 gauge cabling.

I cleaned up and hammerited my battery tray, bolted it through the boot floor and then clamped the battery to that. It ain't going anywhere

The earth cables that run to the negative terminal on the battery at the moment, just bolt them to another part of the body... mine are bolted to the slam panel.

Use cable ties to make sure the cable is clamped in place firmly. You don't want it chaffing on the bodywork.

-westy- · 29 Jan 2008 at 01:44

agw_01 said:
Use a rear seatbelt mounting point for the battery earth. Thin metal will run the risk of overheating and possibly melting.

My seatbelt mounting points are back under the seats, would this be Ok? I've got my rear beam mounting points around there too, I'm assuming they'd be ok to use?

Use an absolute minimum of 4 gauge cabling and fuse it at the battery end. I'm using a 150 amp fuse and 2 gauge cabling.

What do you mean, at the battery end? In the boot?

I cleaned up and hammerited my battery tray, bolted it through the boot floor and then clamped the battery to that. It ain't going anywhere

I was thinking of mounting a plate to the floor of the boot, then mounting the battery onto that, using metal straps. Would that be ok do you think?

The earth cables that run to the negative terminal on the battery at the moment, just bolt them to another part of the body... mine are bolted to the slam panel.

So I'd be able to bolt them to the inner wing, just drill a hole and use a nut & bolt?

One last question - what kind of connection could I use to extend the positive lead towards the boot? I'm assuming chocolate blocks are out the question.. Could I twist & solder the cables together and heatshrink them?

Sorry for all the questions

agw_01 · 29 Jan 2008 at 02:12

-westy- said:
My seatbelt mounting points are back under the seats, would this be Ok? I've got my rear beam mounting points around there too, I'm assuming they'd be ok to use?

Yep. As long as it's a nice big bolt on a strong mounting point you'll be fine.

I know of a few cases where there's been nice melted metal where the mounting surface couldn't handle the current being put through it.

What do you mean, at the battery end? In the boot?

Yep

Have a fuse as close to the battery as possible. Would you believe it, there are people out there who actually recommend not fusing the cable. Yeah ok, it's not my car that could burn out due to an electrical fire.

I was thinking of mounting a plate to the floor of the boot, then mounting the battery onto that, using metal straps. Would that be ok do you think?

Should be ok, just make sure the metal plate and straps are strong. Batteries are easily flung from one side of the boot to the other

So I'd be able to bolt them to the inner wing, just drill a hole and use a nut & bolt?

Should be fine. Where does the negative lead run from the battery at the moment?

One last question - what kind of connection could I use to extend the positive lead towards the boot? I'm assuming chocolate blocks are out the question.. Could I twist & solder the cables together and heatshrink them?

Distribution block

Or, connect everything to the starter motor positive terminal using ring connectors.

-westy- · 29 Jan 2008 at 02:22

agw_01 said:
Yep Have a fuse as close to the battery as possible. Would you believe it, there are people out there who actually recommend not fusing the cable. Yeah ok, it's not my car that could burn out due to an electrical fire.

So I can get a fuse holder and just crimp that into the battery lead?

Should be fine. Where does the negative lead run from the battery at the moment?

It runs down to an earthing plate mounted on the inner wing, so I might be able to either cut it down and terminate it on there, or just run a lead to somewhere else on the inner wing.

Distribution block Or, connect everything to the starter motor positive terminal using ring connectors.

So i'm assuming I can get a distribution block from a motor factors?

agw_01 · 29 Jan 2008 at 02:28

Get the fuse holder, distribution block and other gubbins from any car audio shop

I'll take some pictures of my battery to boot tomorrow to give you an idea of what you need to buy/how to connect it all up.

It's really easy and you shouldn't have any problems doing it.

-westy- · 29 Jan 2008 at 02:53

Fingers crossed

I just really need to free up some space under the bonnet, its very cramped around that area.

With regards to how its mounted in the boot - am I alright to just have it open, with insulated connections for the battery, or better to put it in a box with a hole to vent?

Cupra · 29 Jan 2008 at 03:42

it HAS to be secured down for mot's

if the police pull you over they can give you 3 points for a loose battery

penski · 29 Jan 2008 at 07:44

I would just buy one of the fibreglass battery boxes designed for the job; they have mounting points and so forth already.

Another point which hasn't been covered is:

MAKE SURE YOU USE A SECURE AND INSULATED BOLT TO PASS THE CABLE THROUGH THE BULKHEAD!

I think Lopez covered this off in his 205 build thread.

*n

-westy- · 29 Jan 2008 at 09:44

penski said:
Another point which hasn't been covered is:

MAKE SURE YOU USE A SECURE AND INSULATED BOLT TO PASS THE CABLE THROUGH THE BULKHEAD!

I think Lopez covered this off in his 205 build thread.

*n

Why would I be using a bolt to go through the bulkhead? I'd be using a rubber grommet to make sure the hole isn't dangerous.

I'm assuming some metal strapping will deem the battery 'secured'? I'd be using 2 - crossed over the top of the battery.

Dogbreath · 29 Jan 2008 at 10:10

I think we've been here before, but you should not normally fuse any cable that goes between the battery and the starter motor. Peak current here will be significantly over 150 Amps with a cold engine, and any fuses will just introduce more voltage drop.

If the OEM did not put a fuse in the battery cable (and they almost certainly didn't) then don't put one in there now.

agw_01 · 29 Jan 2008 at 12:31

Dogbreath, as I'm sure you are aware most cars had the battery under the bonnet with very short cable, therefore reducing the need for a fuse.

If you're going to extend that cable throughout the length of the car, I certainly would not run it without a fuse (or some kind of circuit breaker).

I agree about the cranking current, but I've never popped a fuse *touch wood

* even while cranking for a good 10 seconds after an oil change.

You pop the fuse, just swap it out with one that has a slightly higher amperage, but obviously don't exceed the rating of the cable.

OllyM · 29 Jan 2008 at 12:37

I don't think my car has a fuse between the battery (which is in the boot) and the starter motor, and BMW surely know what they're doing when building cars

If it was dangerous, they wouldn't do it without a fuse would they?!

agw_01 · 29 Jan 2008 at 12:41

BMW's were one manufacturer I was thinking of.

They lay the cable while building the car though so obviously route it in the best place.

Laying a cable through your car on your own, having to go over and under things could result in the cable chaffing... no matter how well you run the cable, I'd rather not risk it.

I really really can't believe there are people disputing the use of a fuse on a high current cable. This happened on another forum, I really thought you guys would have a bit more sense