Battery 2 Boot - Part 1

[BraindG]

well, im getting there, just and only just...
carpentry isn’t my thing, but hopefully once ive carpeted it, you’ll never know! :thinking:


Anyhoo, brought a cable up from the front after much huffing and puffing and cursing... (i wish they would make other holes from engine bay to cabin... especially on the manuals..)

After this i stripped out the boot, so that i could figure out how to make the box fit... i was just gonna make a box initially, which would fit the battery exactly, but then two points came up..
1: im wasting space
2: what if the battery has to be changed..

so, after thinking about it over a beer, i decided to make the box you see before you today... after spending a bit of time down at B&Q, trying to figure out a way to secure the battery down, i opted for the clamps currently being used within the engine bay....

mock away :p

[enigma]

Looks OK........apart from the cable........are you sure it is up to the job?? Mos cable is about 10 times bigger!??!

[BraindG]

mo has to run Blackpool illuminations off his :)

[Brind]

mo has to run Blackpool illuminations off his :)

LOL

Watching with interest, but that cable IS too small by the 'looks' of it.
What is its rating?

Remember the further you go the less amperage the cable can cope with.

[BraindG]

its 4 gauge, which is good for 120, the manual alternator only pumps out 85.. more than sufficient your tiptronic alty pumps out a bit more, near 100 i think

[Kieran]

its 4 gauge, which is good for 120, the manual alternator only pumps out 85.. more than sufficient your tiptronic alty pumps out a bit more, near 100 i think

But what about the cranking amperage? Don't you need to oversize to avoid melting the cable when trying to start the car?

[Brind]

Don't forget the cable you have going to your fusebox (the original) is very short and can cope being that size.
And the starter motor is very close as well so it has enough power to crank.

The cable run you have has increased the resistance and is now considerably weaker than a shorter run.
Just think about the run to the starter motor now, was at the most a metre and now it's 3 metres? plus the bends make a difference.

It's not once you're running but the power you need to get it running, just think how much your battery can kick out, 300amps plus!

[wirdy]

Cold cranking amps (CCA on your battery) will exceed 120 amps Barry :wow: .

I use 2-gauge for my banger car (the battery has to sit in a box behind the roll cage) even that got hot one time when I had to crank the car off the track in gear using the starter ;)

IMO although you'll be okay with 4-gauge in 'normal' service, all it takes is a starting problem and you'll be getting a fair bit of heat generated in your cable. Have you ever felt 4-gauge jump leads after a good session trying to start a problem car??

As long as your car starts up like a Mitsubishi should - no probs. :)

Anything more than 30 seconds cranking :thumbsdow

[Pete M]

Another point is that the cable looks to have clear insulation. Isn't this the big fat speaker type cable? My point is that regardless of the wire size (4 gauge), the insulation on the outside has to be suitable. The big fat speaker cable is made to look cool, but it may melt its insulation if you get into the situation of having to crank the engine for a long time. The other point is that the insulation may not be very abrasion resistant. Tucked through body cavities etc, with full battery voltage on it at all times, a short circuit couldn't be stopped without disconnecting the battery. Just be sure that the cable you're using is rated and designed for what you're using it for. I'd be sure to fit a quick disconnect on the battery itself, just in case.

Just my 2 cents worth (wearing my electronics technician hat)....

[wirdy]

....Another point is that the cable looks to have clear insulation. ....

I didn't notice that Pete - you must have a better monitor than me!

Pete's right Barry, that cable is not suited to batteries for the reasons stated. You really need a high density or Nyvin-type insulated cable for this application.

PM me if you would like some, we can come to some arrangement ;)

[Japmetal]

The insulation shouldnt be an issue; I have the exact same cable [mine is Phoenix Gold branded] which IS designed to be power cable, but is made to coordinate with the speaker cable you are confusing it with !

I would agree about rethinking the gauge of cable to be used though; also, MOT regulations state that if your battery is not in the engine bay, it must be in a suitable battery box [available from anywhere that does motorsports-type equipment] incase of spillage/damage. might be worth getting this checked with an MOT station before you get it trimmed & find you have to tear it out again :huh:

[Brind]

Some cable like that is specified as power cable but you will often see a disclaimer suggesting it should not be used on starter motors.

The only reason why they'd say that is: amperage, heat and possibly durability.

[Pete M]

One way to check the cable would be to take it to an Auto Electrician that has a high output battery load tester. This is usually a water-cooled device that tests how well batteries perform under maximum load. If you put a piece of the cable in series, it would show how it dealt with say, 150 Amps.

Of course, I wasn't saying it was speaker cable, but l hadn't seen power cable with that sort of insulation. The nyvin (ah... memories (21 years RNZAF)) type of fibreglass insulated cable is the real stuff. Very durable, small diameter for current capability, heat resistant etc. Probably difficult to source these days. I still have a set of jumper leads I made 30 years ago from some offcuts, and they work better than most of the modern fat ones.

I sure hope you don't have to pull it all the way out of the car again. My Mini (yes, I've got one of those too!) has the battery in the boot, and the battery +ve cable goes out the boot floor and to the front of the car on the outside. I would think this is possibly preferable, as it wouldn't have to go through so many holes in the bodywork, and you could fix it to the inside of the sill, possibly on the way to the front. Just a thought. You'll be regretting telling us about it!

[Nick VR4]

Just thinking here guys

Has the battery been secured in that box

It wont move at all . forward , back if you brake hard or up if you hit a bump etc ??

[BraindG]

this may sound stupid, but what about using normal electrical cable? 25mm (suitable for electrical meter in house) = £1.06 per meter

35mm £2.41 a meter

i know its not very flexy, but whats the argument for not using this?

we're debating the matter here at work you see..

[BraindG]

Just thinking here guys

Has the battery been secured in that box

It wont move at all . forward , back if you brake hard or up if you hit a bump etc ??

nope, it will be as secure as it was in the engine bay if not more so, cos the the side walls

[Nick VR4]

no worries then ;)

[wirdy]

[mine is Phoenix Gold branded] which IS designed to be power cable, but is made to coordinate with the speaker cable you are confusing it with !

I think that's why it's just meant for amplifiers and accessories? :)



...but what about using normal electrical cable?.....but whats the argument for not using this?.

For DC applications- wire is wire, cable is cable; the major advantage of a stranded cable being it's flexibility. If you can bend solid insulated wire to the route you need then there is not a problem. ;)

[BraindG]

at £2 per meter ill get it there :D

[BraindG]

ok, went out and got myself some 0 gauge today... 6 meters, and a couple battery terminals..

60 quid :shifty:

tomorrow, with the help of a mate, were running that down, earthing it all and trying again...

now..
just to recap on the plan..

0AWG from engine to boot... engine side will connect directly to the old + terminal... and obviously other end will connect to + on Batt, with a nice fuse!.. (perhaps directly to starter motor aswell.. will see)

4AWG will connect from the negative on the battery to a nice fresh bit of metal on the body of the car, in the boot... then find a place to earth the front cable... and i should be in business... (or should i leave the 4awg in and use that as the negative?)

[Brind]

You're still going to have the same amperage on the return path too.

However since the body is negative earth you can supply the car with several routes back to the battery so you're not relying on one wire to take the heat so to speak.
Due to body panel welds and resistance through the metal I would take the 4G back to the engine bay, it wouldn't hurt! the more you can supply it the better, obviously there is a limit where it starts to make no difference but I'd rather do that than under supplying the car.

In domestic situations you will have what is called a 'ring' circuit, this is mainly used for your electric sockets.
Basically you come out of the fuse board with a cable, loop your sockets together and then the last socket is then linked back to the fuse board again.
With the two cables you can double the load capacity of the sockets.

[wirdy]

and obviously other end will connect to + on Batt, with a nice fuse!..

WITH A NICE FUSE!!!!!! :undecided

WHY?????????? It'll have to be HUGE! :wow: Like something you'd find in a national grid sub-station!!

Remember cranking your starter motor is 'virtually' a dead short to your battery - you don't need to protect this circuit with a fuse - (the manufacturers don't), your choice I suppose. :thinking:

[Kieran]

Errr.....

For the benefit of Barry and people who like to meddle, would someone care to post how a battery relocation to the boot should be done?

Or have the replies to this post more or less covered it? :thinking:

[wirdy]

Understand your sentiment Kieran :)

You beat me to it. I don't think anyone was meaning to shoot Barry's ideas down - we just wanted him to do a safe installation.
He was good enough to share his progress with us, it's just I can't stand by and watch someone do something that can be done much better - especially when a beloved VR4 could go up in flames :(

I think we've covered most points in this thread. The battery box question hasn't been put to bed AFAIK? I'd get one if I was doing this mod - regardless of the MOT regs ;) .

[Kieran]

Cool:)

As long as all the bases are covered, that's all good in the hood :-D

/notes this thread for future reference and pencils idea into 'Cunning GLS Plans' book.... :devil5:

[Brind]

This is something you do NOT want to mess about with if you're not sure what you're doing!
As Wirdy just pointed out, "could go up in flames".

One of the main misconceptions of electricity is voltage and its potential amperage.
Just because your car battery is only 12 Volts the amps in this situation is potentially 4 times HIGHER than what it supplying your house!

I don't see why a new thread should be made, the only change is the cable size.

[Japmetal]

Having done some building work on the side these pst few weeks, I may be refitting my boot with a false floor etc to take my sub box & if all goes according to plan should be relocating my battery too; When I do, I'll take some pictures, we can iron out the kinks [debates !] in the setup & I'll do a proper 'How-To" write up for you to stick in your members area :)


AND just for the record, that cable is fit for anywhere in your electrical system - although I'd agree that the main feed for your starter may be pushing it a bit !

[BraindG]

its all done... will show photos once the box is carpeted etc

[wirdy]

......The nyvin (ah... memories (21 years RNZAF)) type of fibreglass insulated cable is the real stuff. Very durable, small diameter for current capability, heat resistant etc. Probably difficult to source these days.......
Not difficult to source if you're still on the 'inside' Pete ;) :boing4:




AND just for the record, that cable is fit for anywhere in your electrical system - although I'd agree that the main feed for your starter may be pushing it a bit !

I wouldn't trust it for battery cable on my car mate. It may be oil, fuel and 105c temp resistant, but it's primarily designed for audio power hook ups. If you're going to do the job properly then use proper DC power cable. You also pay a big premium for it to look nice with the clear PVC coating - but if you're putting it under the carpet- why bother? Normally these cables only go up to a maximum size of 4 gauge anyway, which isn't man enough for the current that's drawn on start-up. See cable current load (http://www.powerstream.com/Wire_Size.htm) for a non cable-specific guide. Barry's got it about right with zero gauge. I checked my banger car battery cable and it's 000 gauge!! :rolleyes5 Well up to the job!!

Although I admit I probably over-spec most of my cabling, just to have a safety margin of >25% of max load, I think Pete M will agree that if it's used on aircraft then that's a good indication. If they ever start using this type of clear insulated cable on aircraft then I'll drop by for dinner to eat some of your freshly cooked humble pie. :-D :-D