was sent this via email. what size wire to use

zippy656 · 10-06-2009, 21:52

	Ginny Simkins

Dear Steve

Please see below:

Sq mm Rating in Amp
0.2 1.4
0.35 3.2
0.5 1.0
0.75 14.0
1.0 16.5
1.5 21.0
2.0 25.0
2.5 29.0
3.0 33.0
4.0 39.0
6.0 50.0
10.0 70.0
16.0 110.0
25.0 170.0
35.0 240.0

Depending on load: eg 1 headlight @ 55W dividethis by lowest expected
voltage (during cranking) eg 11.5~12v, which gives a figure of 4.8 amps on a
12 v vehicle so the wire required is 0.5sqmm.

If you are using more than one piece of equipment on a wire, just add them
up and do same as above. Adjust for 24V vehicles (min @ crank is ~20v).

As far as measuring a piece of string will be fine although we like to use a
piece of 7 core trailer cable which behaves more like a loom around corners
etc.

Hope this helps

Best regards

Ginny

Deleted account DD · 10-06-2009, 22:13

excellent stuff

ssteve · 10-06-2009, 22:21

Quote:

Originally Posted by zippy656

from www.simtekuk.co.uk‏

	Ginny Simkins

Dear Steve

Please see below:

Sq mm Rating in Amp
0.2 1.4
0.35 3.2
0.5 1.0
0.75 14.0
1.0 16.5
1.5 21.0
2.0 25.0
2.5 29.0
3.0 33.0
4.0 39.0
6.0 50.0
10.0 70.0
16.0 110.0
25.0 170.0
35.0 240.0

Depending on load: eg 1 headlight @ 55W dividethis by lowest expected
voltage (during cranking) eg 11.5~12v, which gives a figure of 4.8 amps on a
12 v vehicle so the wire required is 0.5sqmm.

If you are using more than one piece of equipment on a wire, just add them
up and do same as above. Adjust for 24V vehicles (min @ crank is ~20v).

As far as measuring a piece of string will be fine although we like to use a
piece of 7 core trailer cable which behaves more like a loom around corners
etc.

Hope this helps

Best regards

Ginny

11.5- 12.0 volts at cranking! a bit optimistic?

especialy when 24 volt system lost 4 volts??

ssteve

extreme-4x4 · 10-06-2009, 22:56

you mean someone understood all that ?

i just thought he was posting his spam mail here

zippy656 · 11-06-2009, 05:42

ehehehhe
i could do that, but take way to long!

Deleted account DD · 11-06-2009, 07:09

well I'll

for zippy.

I can never find what mm wire for the power when I need to

zippy656 · 11-06-2009, 08:37

Thanks dave.. at least some one else found it usefull

extreme-4x4 · 11-06-2009, 09:04

no its good, even better you shared it

i just didnt understand it

zippy656 · 11-06-2009, 09:11

Quote:

Originally Posted by extreme-4x4

no its good, even better you shared it

i just didnt understand it

who said i did!

ocelot · 11-06-2009, 09:22

I always find it more useful to add 100% to cable size for currents up to 10A @ 12vdc, for battery/power requirements (winches etc) I use 16-18mm singles, for most other things, 4mmsq will do the job.
If really low current, 12v cig sockets for gps etc, 1.5mm flex will do the job but remember to put fuses in line.......... otherwise you could end up with burnt cable or worse...........
I work in marine electronics so well used to 12 and 24vdc systems running for 20 meters or so, if the cable is too thin, the volt drop is considerable, the thicker the cable, the better the efficiency, to a point, resistance then comes into play over very long distances..... ie, over 20m @ 12vdc

zippy656 · 11-06-2009, 09:26

that sounds like a good idea, always use more than you think you will,.

im after adding 3 lights sockets into the boot area, what you think i shoul duse for that then?

fuse box better than inline ones?

ocelot · 11-06-2009, 09:36

depends on the current the lights draw,

w=I squared x resistance,
or
W (watts) = I (current) x V(volts) translate that into
I=W/V

Take your total wattage and divide it by the voltage.

if you're using 75 watts (3x25w 12 lamps) divide that by 12vdc to give you the current draw, which is in the 6A region, so you'd need 2.5mm cable but allowing for headroom because you'll always fit something else too....... try 4mm sq, use singles so you get more into a tight space, cable tie at 6" intervals if you can and use a fuse box, don't forget to use the right fuse for the job, if the load's 6A use a 10A fuse, again, for headroom but the fuse will blow if shorted because the battery will try to shove the current down the easiest route, ie a short cct........

zippy656 · 11-06-2009, 09:43

oops lighter sockets.. for fridge, orange flashing lights ( 2 x 25w ) , cb, inverter ( 150w ) phone sat nav, phone, compresser.

ok, not all at same time though, well I hope not at least, but should be ok to do so if really needed

Terranosaurus · 11-06-2009, 09:58

The above specs are for modern thinwall cable (which i always use), however the stuff you are likely to come across unless you specifically buy thinwall has much lower ratings

1mm2, 8.75amp.
2mm2, 17.5amp.
3mm2, 27.5amp.
4.5mm2, 35amp.
6mm2, 42amp.
7mm2, 50amp.
8.5mm2, 60amp.
10mm2, 70amp.

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10-06-2009, 22:13	#2
Deleted account DD Senior Member Join Date: Sep 2008 Posts: 4,705	excellent stuff

10-06-2009, 22:56	#4
extreme-4x4 Senior Member Join Date: Sep 2008 Location: WALES Posts: 6,295	you mean someone understood all that ? i just thought he was posting his spam mail here

11-06-2009, 05:42	#5
zippy656 Senior Member Join Date: Aug 2008 Location: Devizes Wiltshire Vehicle: Nissan Note Ntec 1.5 Posts: 14,138	ehehehhe i could do that, but take way to long!

11-06-2009, 07:09	#6
Deleted account DD Senior Member Join Date: Sep 2008 Posts: 4,705	well I'll for zippy. I can never find what mm wire for the power when I need to

11-06-2009, 08:37	#7
zippy656 Senior Member Join Date: Aug 2008 Location: Devizes Wiltshire Vehicle: Nissan Note Ntec 1.5 Posts: 14,138	Thanks dave.. at least some one else found it usefull

11-06-2009, 09:04	#8
extreme-4x4 Senior Member Join Date: Sep 2008 Location: WALES Posts: 6,295	no its good, even better you shared it i just didnt understand it

11-06-2009, 09:22	#10
ocelot Senior Member Join Date: Jun 2009 Location: merseyside Vehicle: Nissan Terrano 2.7 Posts: 242	I always find it more useful to add 100% to cable size for currents up to 10A @ 12vdc, for battery/power requirements (winches etc) I use 16-18mm singles, for most other things, 4mmsq will do the job. If really low current, 12v cig sockets for gps etc, 1.5mm flex will do the job but remember to put fuses in line.......... otherwise you could end up with burnt cable or worse........... I work in marine electronics so well used to 12 and 24vdc systems running for 20 meters or so, if the cable is too thin, the volt drop is considerable, the thicker the cable, the better the efficiency, to a point, resistance then comes into play over very long distances..... ie, over 20m @ 12vdc

11-06-2009, 09:26	#11
zippy656 Senior Member Join Date: Aug 2008 Location: Devizes Wiltshire Vehicle: Nissan Note Ntec 1.5 Posts: 14,138	that sounds like a good idea, always use more than you think you will,. im after adding 3 lights sockets into the boot area, what you think i shoul duse for that then? fuse box better than inline ones?

11-06-2009, 09:36	#12
ocelot Senior Member Join Date: Jun 2009 Location: merseyside Vehicle: Nissan Terrano 2.7 Posts: 242	depends on the current the lights draw, w=I squared x resistance, or W (watts) = I (current) x V(volts) translate that into I=W/V Take your total wattage and divide it by the voltage. if you're using 75 watts (3x25w 12 lamps) divide that by 12vdc to give you the current draw, which is in the 6A region, so you'd need 2.5mm cable but allowing for headroom because you'll always fit something else too....... try 4mm sq, use singles so you get more into a tight space, cable tie at 6" intervals if you can and use a fuse box, don't forget to use the right fuse for the job, if the load's 6A use a 10A fuse, again, for headroom but the fuse will blow if shorted because the battery will try to shove the current down the easiest route, ie a short cct........

11-06-2009, 09:43	#13
zippy656 Senior Member Join Date: Aug 2008 Location: Devizes Wiltshire Vehicle: Nissan Note Ntec 1.5 Posts: 14,138	oops lighter sockets.. for fridge, orange flashing lights ( 2 x 25w ) , cb, inverter ( 150w ) phone sat nav, phone, compresser. ok, not all at same time though, well I hope not at least, but should be ok to do so if really needed

11-06-2009, 09:58	#14
Terranosaurus Senior Member Join Date: Aug 2006 Location: YORKSHIRE Vehicle: 2001 2.7 TDi T2 SWB Posts: 4,077	The above specs are for modern thinwall cable (which i always use), however the stuff you are likely to come across unless you specifically buy thinwall has much lower ratings 1mm2, 8.75amp. 2mm2, 17.5amp. 3mm2, 27.5amp. 4.5mm2, 35amp. 6mm2, 42amp. 7mm2, 50amp. 8.5mm2, 60amp. 10mm2, 70amp.