hi steve,

yes you can do that with the battery

ps LR is landrover ;-)

BearDy89 said:

Unless someone corrects me.
the ignition live just tells the stereo to turn off when the car turns off, the power is fed from the Permenant live which as Station House says also allows it to hold its memory when the power is turned off.

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Bear, I think you'll be pleased with me. So far:

I've installed the relay and 4 way fuse box, screwed onto a painted wooden backing board that's riv-nutted onto the inside of the battery box.

Have connected the relay live to battery live, and the relay earth to battery earth. Just need to run ignition cable from relay to ciggie lighter splice, and 16A wire from 4 way fuse box to stereo (stereo mounting arrived today.) Pics of setup on their way just as soon as I've run some more wires.

Thing is, there appears to be loads of spare/unconnected connections beneath the dash tray that I've removed, and I was wondering: perhaps one of these could provide the direct 12V feed from the battery/engine fuse box that the stereo also needs? If possible, how would I test to ensure one of these wires is suitable for the job?

Also, the stereo has a 10A fuse in it's backside. If I do have to run a wire from directly from battery live then can I get away with using a 16A wire? I have 30A available too. Just needed to be extra sure about what level of current the battery might draw before remounting the dash and all the other bits and bobs.

Thanks

I'll leave Sam to award you marks out of 10 once we see the piccys

Answering your questions

1) 16 amp cable will be fine

2) Live feeds - using your meter with the sharp pointer probes, connect the black probe to earth (screws on the fuse box housing are good) and see if you ccan find one which gives a 12v reading

Know you'll be wondering whether the wire is thick enough for the job - unless it is incredibly thin, it should be fine

Glad you've made such great progress

I await pictures for marking.

Agree with SH on all other points.

no real way to test what a cable is able to handle in terms of current(amps) only way you can guess is if you compare to a known size I.e the 16 and 30A cable you already have.

If you really want to calculate it, this explains:

http://www.tlc-direct.co.uk/Book/4.3.9.htm

Personally I'd just make sure (as Sam suggests) that the wire you decide to use is not too much thinner (the copper wire that is, not the insulation diameter as insulation thickness can vary for the same rated cable) than the 16A stuff you already have.

Station House said:

If you really want to calculate it, this explains:

http://www.tlc-direct.co.uk/Book/4.3.9.htm

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haha i meant theres no real way to test what size a cable is (Current capability) unless you have a degree in physics and maths

BearDy89 said:

haha i meant theres no real way to test what size a cable is (Current capability) unless you have a degree in physics and maths

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Now that I do agree with - i didn't say I understood how to do the calculation

RMS output is about 70% of peak output, and peak to peak is double peak output. Peak output is not about short term maximum output, like say a generators peak output, it's the highest positive voltage of the output waveform.
A lot of manufacturers like to boast about their large amplifier outputs so as most of them are stereo they quote 2 x peak to peak output.

Incidentally our 240v mains electricity is the RMS value so if you were to use the peak to peak value it would be About 650 volts.
It all came about to give a comparison with DC. If you feed 240vdc into a heater you would get the same heating effect out as feeding 240vac rms into the same heater.

Hope this helps in a small way lol

Probably not.

But thanks