flibble
|
| posted on 1/5/11 at 09:49 PM |
|
|
Battery cable, does size matter?
Silly question probably but...
I had to run a battery cable from the boot through the trans tunnel to the fuses/relays etc under the scuttle (2.5m), I used an offcut of cable from
work but am now wondering if large cable has any detrimental effect on voltage drop etc, tried to have a "first start" of the engine today
and it struggled to turn over and just wondered if it's a possibilty, if not then it's a new battery needed (which I strongly suspect).
The cable is about 20mm2.
Cheers
Kev
|
|
|
|
|
MikeRJ
|
| posted on 1/5/11 at 09:55 PM |
|
|
For high current cables the larger the better.
|
|
|
flibble
|
| posted on 1/5/11 at 09:57 PM |
|
|
Ahh, I see, never did understand electrickery.. Although that means im gonna have to splash out £70 for a new battery now  Booo.
Cheers!
|
|
|
plentywahalla
|
| posted on 1/5/11 at 10:11 PM |
|
|
Your starter will draw 200 amps minimum, more when cold possibly 300 amps. 20 sqmm is rated at only 100 amp so over a long length you will get serious
voltage drop.
Use the heaviest cable you can, 40 or 60 if you can get it.
|
|
|
flibble
|
| posted on 1/5/11 at 10:17 PM |
|
|
Ahh but it's 20mmx20mm, (closer to 25x25 actually) not 20 square mm, which is why I wondered if it was too big 
|
|
|
MakeEverything
|
| posted on 1/5/11 at 10:23 PM |
|
|
quote:
Originally posted by flibble
Ahh but it's 20mmx20mm, (closer to 25x25 actually) not 20 square mm, which is why I wondered if it was too big
Cable is measured by the cross sectional area of the conductor.
You wont get any noteable voltage drop over 2.5m. 25m, maybe. Go to an electrical wholesalers and ask for 25mm tri-rated cable. I dont believe you
can get this stuff in 20mm.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
|
|
|
flibble
|
| posted on 1/5/11 at 10:39 PM |
|
|
Aww, I'm confused now, lol
I guessed at the 20mm measurement but putting the verniers across the bare wire (not the insualtion) it measures 23.9mm, I can't believe
it's too small, its at least 3x the size of the battery wire on my daily SAAB!
It's got the same strand size as the normal auto wire I got from VWP, so not the heavy gauge thick cores.
|
|
|
iank
|
| posted on 1/5/11 at 10:59 PM |
|
|
If it truly is 23.9mm diameter conductor it's over 450mm^2 (!!!)
The downside will be the weight and the unwieldiness of using it - 60mm^2 (od with insulator of around 15mm) is good for 415A yours will be ok in the
multiple 1000A's.
ETA: Assuming it's copper
[Edited on 1/5/11 by iank]
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
|
|
|
HowardB
|
| posted on 1/5/11 at 11:32 PM |
|
|
i used some spare arc welding cable on mine plenty thick enough, (about 1/2" your cable sounds as though it designed for a power station!
Howard
Fisher Fury was 2000 Zetec - now a 1600 (it Lives again and goes zoom)
|
|
|
James
|
| posted on 2/5/11 at 12:24 AM |
|
|
A v8 BMW 740 has the battery in the boot, which in a car that long means cable about 100m long! 
It's about 13mm thick... I have one as it was only about £5 from the scrappy. Must be worth more than that scrap metal value now! 
So if 13mm is enough for a v8 starter and all the 740's gadgets... it'll be more than enough for your little car!
Dont weigh it all down with 100kg of copper!
Cheers,
James
------------------------------------------------------------------------------------------------------------
"The fight is won or lost far away from witnesses, behind the lines, in the gym and out there on the road, long before I dance under those lights."
- Muhammad Ali
|
|
|
RazMan
|
| posted on 2/5/11 at 07:36 AM |
|
|
quote:
Originally posted by iank
If it truly is 23.9mm diameter conductor it's over 450mm^2 (!!!)
That would start a whole carpark!! How on earth did you find a connector to fit that? maybe from the battery room of an old Russian sub??
[Edited on 2-5-11 by RazMan]
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
|
|
|
jeffw
|
| posted on 2/5/11 at 07:50 AM |
|
|
Got a weigh a lot as well. 24mm diameter conductor is enormous.
|
|
|
omega 24 v6
|
| posted on 2/5/11 at 08:18 AM |
|
|
Remember to complete the circuit you also need an earth wire. I presume you are using the chassis for this??? If so then make sure all earth points
are clean and secure. If not ,and you have run a cable ( any cable from the battery to earth) it needs to be of the correct size as well.
If it looks wrong it probably is wrong.
|
|
|
flibble
|
| posted on 2/5/11 at 09:05 AM |
|
|
Lol, yes it is quite big, and someone guessed correcty, I believe it's grounding cable for one of the substations that keep the site running
(industrial chemicals). It only has maybe 2-3mm of insualtion oddly, although that's not a problem as I've run it through B&Q white
PVC(?) pipe so it's well p[rotected. Not sure if it's copper, its the same fine silver strands that my tiny thinwall cable uses?
On a side-rant:
It's amazing what some big companys throw away (this was in a skip, about 50m of it), and it was a general waste skip, not the dedicated
recycling skip. There were also umpteen solid lumps of stainless (used for counterweights in the food side of the factory, so food grade 316 I
assume), that were about 12" diameter and 18" tall, weighed a ton and real struggle to lift. Endlesss flat screen monitors under a year
old, massive helical gearsets off something industrial that were still in the wrappers and said to be worth thousands and TONS of other stuff, etc,
etc, . all being dumped.. and why..?
All beacuse the american HQ top dogs were coming over for a look around tour UK site (on a money saving mission ironically) and all this looked
untidy.
I asked if I could Ebay it and split the profits with the company but no, all to be dumped 
|
|
|
snowy2
|
| posted on 3/5/11 at 09:11 PM |
|
|
fibble him of B+ fame?? if so i i could have answered your comment elsewhere ;-)
should have read your profile a bit more.......Hi Fibble :-)
[Edited on 3/5/11 by snowy2]
|
|
|
flak monkey
|
| posted on 4/5/11 at 06:54 AM |
|
|
16-20mm^2 will be plenty even with the battery at the back
Current capacities are the continuous load ratings. Starters only draw for a few seconds. Most car starters are rated at around 1.5kW which I make to
be 125amps...
Use welding cable, nice and flexible and rated to at least 200amp continuous
Sera
http://www.motosera.com
|
|
|
wilkingj
|
| posted on 4/5/11 at 04:43 PM |
|
|
You have made an earth cable from the chassis to the engine?
Same size as the Battery to Starter solenoid cable, as it carries the full current when starting the engine.
Also make sure you scrape the paint away down to the bare metal when you make any earth connections.
Cheers
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
|
|
|
flibble
|
| posted on 4/5/11 at 05:03 PM |
|
|
Cheers for the replies,
Yes, I've earthed the chassis to the engine, almost 100% sure it's the battery now, will have to go to Halfords and see if they'll
exhcange without a receipt (only 18 months old), If not then £70 for a new one.
Measuring across the terminals after charging for 16hrs showed 12.8v which is normal I think, but goes straight down to 8-9v when starter button is
pushed. It then slowly recovers back up to 11-12v but takes a few minutes.
Hi Snowy!
[Edited on 4-5-11 by flibble]
|
|
|
