Club 80-90 Forums

Hello, me again!

Finally got round to buying a second battery at the weekend to use as a leisure battery. Been on the Wiki and seen the various entries about wiring up and have gone down the 'smartcom orange box of tricks' route.

Been a bit of a numpty but keen as mustard, what gauge wire should I use from my starter battery to the smartcom relay and again from the relay to the leisure battery? Also, what gauge should I then use from the leisure battery to secondary fuse box / ancillary devices?

Could someone give me an idea of how the gauge of wire and fuse rating works - what is the logic / protocol to follow? If I can get the general idea I should be okay from there....

Thanks,

Chris

Hello again

The size of wire needs to be matched to what you plan to power up to a maximum stated on the relay.

A rough guide is below for 12V DC running less than 3 Meters. Be carful and always use a fuse rated less than the current rate of the wire. If you draw too much current through a small wire it will turn the wire in to a heater. Best way to think of it is how much current am I going to draw from the battery. Then match the cable and protect it with a matched fuse.

A AWG
5 16
10 12
15 10
20 10
25 8
30 8
35 6

Hi Kev,

I'm getting my money's worth out of you!

Thanks for this - makes sense, kind of.

So, to be clear from your table, if I am using a piece of kit drawing 5 amps, what does the 16 AWG? Is this the wire gauge in mm? Again, sorry if I'm being dim here!

Also, how much less would the fuse normally be rated below the wire?

And finally, what about where I will be running from my leisure battery to the secondary 8 way fuse box which will have lots of kit hooked to it - what gauge should be used here?

Cheers, Chris

anyone, anyone??

1.5mm takes up to 20A
2.5mm takes up to 27A

Figures based on mains voltages but that's by the by - it's current that matters. Figures also based on reasonable heat dissipation so don't bury cables in carpet, thermal insulation or the like.

Hi Chris

I usually match the fuse to the item the circuit is powring then use the next cable up.
eg my fridge draws 7.5A I protect it with a 8A fues and use 1mm wire.
I also have a 12V outlet which is protected by a 15A fuse and uses 2mm wire.

If you are using automotive cable there are two types standard and thinwall.

Typical continuous current values are

Standard

1mm 8.75A
2mm 17.5A
3mm 27.5A
4.5mm 35A
6mm 42A
7mm 50A
8.5mm 60A
10mm 70A

thinwall

.5mm 11A
1mm 16.5
2mm 25A
3mm 33A
4 39A
6 50A

K

Thanks again for your help guys! I'll try not to blow anything up!!

Chris